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Morphological studies on the beet armyworm Spodoptera exigua (Hubner) (Lepidoptera: Noctuidae)

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Morphological studies on the beet armyworm Spodoptera exigua (Hubner) (Lepidoptera: Noctuidae)
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Spodoptera exigua (Hubner) (Lepidoptera: Noctuidae)
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Ngo Dong, 1937-
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xiii, 118 leaves : ill. ; 28 cm.

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Subjects / Keywords:
Antennas ( jstor )
Armyworms ( jstor )
Beets ( jstor )
Eggs ( jstor )
Female animals ( jstor )
Insect antennae ( jstor )
Instars ( jstor )
Moths ( jstor )
Scent glands ( jstor )
Sensilla ( jstor )
Beet army-worms
Dissertations, Academic -- Entomology and Nematology -- UF
Entomology and Nematology thesis Ph. D
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bibliography ( marcgt )
non-fiction ( marcgt )

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Thesis:
Thesis--University of Florida.
Bibliography:
Bibliography: leaves 113-117.
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Typescript.
General Note:
Vita.
Statement of Responsibility:
by Ngo Dong.

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MORPHOLOGICAL STUDIES ON THE BEET ARIMYWORM
SPODOPTERA EXIGUA (HUBNER) (LEPIDOPTERA: NOCTUIDAE)












By

NGO DONG












A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL
OF THE UNIVERSITY OF FLORIDA
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY




UNIVERSITY OF FLORIDA 1974





























To my wife, Ton-Nu Thanh-Chau

and my children,

Ngo Bao, Ngo Quynh, Ngo Anh, Ngo Anh-Thu.













ACKNOWLEDGMENTS

The author is greatly indebted to Dr. Dale H. Habeck as chairman of the Supervisory Committee for his guidance, criticisms, and valuable suggestions in carrying out the work and organizing the material for this dissertation. Further appreciation is expressed to Dr. Habeck for supplying the laboratory and photographic supplies necessary for this research.

Deep appreciation is expressed to Dr. Harvey L.

Cromroy, Departments of Entomology and Radiation Biophysics, who has offered valuable assistance to the author.

The author wishes to express his gratitude to Mrs.

Thelma C. Carlysle for her aid with the use of the scanning electron microscope, darkroom work, and the histological slides. Grateful acknowledgment is given to Dr. Derrell Chambers for providing facilities in the Insect Attractants, Behavior and Basic Biology Research Laboratory, USDA, Gainesville, and to Dr. Thomas C. Emmel for helping in the chromosome study.

Special thanks are extended to Dr. Dale Habeck, Dr.
Harvey Cromroy, Dr.. Milledge Murphey, Dr. Louis C. Kuitert and Dr. James Soule who have taken the time to edit and criticize this dissertation.

iii









A special debt of gratitude is likewise due to

Dr. Le Thanh Minh Chau, Rector of the University of Hue and Mr. Freddie A. Johnson for their constant help and encouragement.

Thanks are also due to Mary Davis, Larry Moody, Ed Sroka, Melinda Chancy and Jo Ann Salter for typing, illustrating and printing this manuscript.

Last but not least, the author wishes to express
his sincere appreciation to his wife, Ton Nu Thanh Chau, for the encouragement and understanding she has given throughout the author's graduate work.




























iV















TABLE OF CONTENTS


ACKNOWLEDGMENTS ........... . . . iii

LIST OF TABLES . . . . . . . . . vi

LIST OF FIGURES . . . . . . . . . vii

ABSTRACT . . . . . . . .. . . xii

CHAPTER

I. INTRODUCTION . . ........... 1

II. LITERATURE REVIEW .. .. .... ... 3

III. METHODS AND MATERIALS . . . . . 8

A. Rearing . . . . . . . 8
B. Gross Morphological Studies. . . 8 C. Chromosome Number. . . . . . 9
D. Scanning Electron Microscope . . 10

IV. RESULTS AND DISCUSSION .... .... 12

A. Moth . . . . ... . . . 12
1) Antennae. . . . . . . 12
2) Wings . . . . . . . 40
3) Scent Glands . . . . . 6
4) Reproductive System . . . . 70

B. Egg . . . . . . . . 97
C. Larva. . . . . . . . .. 97
D. Chromosome Number. . . . . .102

V. CONCLUSIONS . . . . . . . .112

VI. LITERATURE CITED ........... .. 113

VII. BIOGRAPHICAL SKETCH . . . . . .118



V
















LIST OF TABLES


Table 1. Comparison of antennal flagellar
segment length in beet armyworm . . 13 Table 2. Measurements and proposed functions
of sensilla on beet armyworm antenna. . 19 Table 3. Measurements of female internal
reproductive organs and spermatophore . 79 Table 4. Measurements of male internal
reproductive organs .......... 80































vi















LIST OF FIGURES


Figure 1. Beet armyworm moth, male ........ 21 Figure 2. Beet armyworm moth, female ... .... 23 Figure 3. Dorso-lateral view of antennal
segment showing convergence of scale surface with sensory surface. Distal portion of antenna with dorsal surface to the right
(X898) . . . . . . . . 25

Figure 4. Lateral view of the ventral
surface of the basal portion
of antenna (X705) . . . . . 25

Figure 5. Most distal segment of the antenna
showing sensors covering most of
the circumference (X1410). .... . 27 Figure 6. Chaeticum and trichodea on segment
near base of antenna (X2926) ..... 27 Figure 7. Bohm bristles on scape dome of male
(X900) ...... ............... Z9

Figure 8. Close-up of Bohm bristles on scape
dome of female (X2667) . . . . 29 Figure 9. Close-up of chaeticum on the antenna
(X7182) . . . . . . . . 31

Figure 10. Sensilla auricillica and button-like
sensor (X7049) . . . . . . 31

Figure 11. Close-up of chaeticum (X6835) . . . 33 Figure 12. Short porous trichodea (X'T17r40) . . 33 Figure 13. Long porous trichodea (X5060) . . . 35 Figure 14. Long porous trichodea (X13,333) .... 35 Figure 15. Non-porous trichodea (X6835) . . . 37



vii









LIST OF FIGURES (Continued)

Figure 16. Sensilla coeloconica (X6650) ..... 37

Figure 17. Sensilla auricillica (X6835) ......... 39

Figure 18. Sensilla styloconica (X4430) ...... 39

Figure 19. Fore- and hind-wing (dorsal) surface showing zonal division for
both males and females (zone 1
shaded, zone 2 unshaded) ....... 46

Figure 20. Upper: zonal division of forewing
(ventral surface) in males
Middle: zonal division of forewing
(ventral surface) in females
Lower: zonal division of hindwing
(ventral surface in both males
and females. ...... ........ . 48

Figure 21. Dorsal forewing scales in zone 1
(X253) . . . . . . . . 50

Figure 22. Dorsal forewing covering and basal
scales in zone 2 (X253) ....... 50

Figure 23. Border scales on dorsal forewing
(X253) . . . . . . . 5

Figure 24. Scales on ventral forewing in zone 1
(X253) . . . . . ... . 2

Figure 25. Basal scales and covering scales on
ventral forewing in zone 2 (X253). ... 54

Figure 26. Scales on ventral forewing in zone 3
(X253) ... ....... .... 54

Figure 27. Spine-like scales on posterior base
of ventral forewing on sac-like structure and regular scales in
zone 3 (X226) . . . . . . 56

Figure 28. Ultrastructure of scales in zone 3
(X6317) ... . . . . . . 56

Figure 29. Scales on anterior anal area of the
forewing (female, ventral) (X4522) . 58

Figure 30. Scales on anterior anal area of the
forewing (male, ventral ) (X2660) . 58


viii










LIST OF FIGURES (Continued)

Figure 31. Dorsal hindwing: scales in zone
1 and piliform scales (X253) ..... 60

Figure 32. Dorsal hindwing: scales in zone
2 (X253) . . . . . . . .. 60

Figure 33. Ventral hindwing: scales in zone
1 (X253) . . . . . . . . 62

Figure 34. Ventral hindwing: scales in zone
2 (X253) . . . . . . . ... 62

Figure 35. Ultrastructure of orange scale
showing high longitudinal ribs
and circular cross-ribs (X4985) . .. 64

Figure 36. Ultrastructure of gray scale showing
shallow grooves and irregularly
patterned cross-ribs (X5852) ..... 64

Figure 37. Ultrastructure of scale on ventral
hindwing in zone 2 showing smooth
groove without perforations (X4985) 66

Figure 38. Ultrastructure of border scale on
ventral hindwing showing smooth
groove with perforations (X5852) .... 66

Figure 39. Ultrastructure of the scale on dorsal
forewing in zone 2 showing straight
cross-ribs (X4985) . . . . . 68

Figure 40. Ultrastructure of scale on dorsal
hindwing in zone 2 showing curved
cross-ribs (X4985) . . . . . 68

Figure 41. Scent glands located between VIIIth
and IXth abdominal segments. Dark
color: sclerotized area ....... .72

Figure 42. The scent gland in the intersegmental
area between the 9th sternite and
the 8th sternite..... ............ 74

Figure 43. Close-up showing wavy surface of
the scent gland and glandular
cells underneath .......... . 74

Figure 44. Ovipositor showing sensilla on extreme
tip (X133) .. .............. 82

ix









LIST OF FIGURES (Continued) Figure 45. Close-up of ovipositor opening
(X253) ................. 2

Figure 46. Close-up of ovipositor (X253). ..... ...84

Figure 47. Sensilla on dorsal posterior
ovipositor (X1330) . . . . . .84

Figure 48. Dorsal view of male genitalia
(X665) . . . . . . . . .86

Figure 49. Male tegumen supporting uncus with
claspers on either side (X825) . . ....86 Figure 50. Dorsal view showing uncus and
claspers (X66) . ... ... .. . . .88

Figure 51. Inside surface of claspers of
male genitalia (X452) . . . . .88 Figure 52. Sensilla and scales on outside
of the clasper; male genitalia (X1463) .90 Figure 53. Ultrastructure of scale inside of
clasper; male genitalia (X7182) . . .90 Figure 54. The female reproductive system . . . .92 Figure 55. The spermatophore ........... .94

Figure 56. The male reproductive system .... . .96 Figure 57. Beet armyworm eggs partly covered
with scales from tip of female
abdomen (X133) . . . . . . .99

Figure 58. Apex of egg showing micropyle and
chorion design (X931) . . . . .99 Figure 59. Egg surface showing aeropyles (pores)
on edge of ridges (X1430) ....... 101 Figure 60. Ocelli and antenna of first instar
larva, dorso lateral view (X665) . . 101 Figure 61. Microspines and setae on first
instar larva (X1596) . . . . 104 Figure 62. Spiracle of first instar larva
(1410) . . . . . . . . 104

Figure 63. Overall view of anterior portion of
first instar larva (X300) . . . 106

x









LIST OF FIGURES (Continued)


Figure 64. Chromosomes of the beet armyworm
observed under microscope with
phase (n=31) (X1197) . . . . 109 Figure 65. Chromosomes of the beet armyworm
observed under microscope without
phase (X1197). . . . . . 109

Figure 66. Bundles of sperms in testis (X1197) . 111 Figure 67. Two sperms among nucleus division
in testis (XI197) . . . . ll


































xi











Abstract of Dissertation Presented to the
Graduate Council of the University of Florida
in Partial Fulfillment of the Requirements for the
Degree of Doctor of Philosophy


MORPHOLOGICAL STUDIES ON THE BEET ARMYWORM
SPODOPTERA EXIGUA (HUBNER) (LEPIDOPTERA: NOCTUIDAE) By

Ngo Dong

June, 1974

Chairman: Dale H. Habeck
Major Department: Entomology and Nematology

The beet armyworm Spodoptera exigua (Hubner)

(Lepidoptera: Noctuidae), a nearly cosmopolitan species, is an economically important pest in Florida and other areas. Morphological studies were concentrated on the antenna, wing scales, and the external genitalia and reproductive system of the adult, the egg, and first instar larva.

Female antennae are longer than male antennae. Six morphologically distinct types of sensilla were found on the antennae of each sex: Bohm bristles, chaetica, trichodea, auricillica, styloconica and coeloconica. However, only the male has the long sensilla trichodea. These are arranged in a distinct pattern. Wings can be divided into distinct zones based on types of scales:




xii










two zones in forewing (dorsal), hindwing (dorsal and ventral), and three zones in forewing (ventral). Scent glands are present in the ventral intersegmental area between the 8th and 9th abdominal segments. Three types of sensilla are found on the lateral plates forming the ovipositor. The 9th abdominal segment of the male has a curved uncus and two lateral hooks arising from the claspers. Externally, there are many more scales and very few sensilla on the male genitalia compared to the female. The female ovary is composed of four ovarioles and development is panoistic.

The egg chorion around the micropyle is shaped

petal-like with 7 11 lobes. Many tiny aeropyles occur on the edge of egg ridges.

The first instar larva is covered with microspines. Head setae tend to be sharp, curved and without raised pinaculum while body setae are straight and blunt tipped with pinaculum.

The haploid chromosome number for this species was determined to be n=31.














xi)i














CHAPTER I

INTRODUCTION


The beet armyworm Spodoptera exigua (Hubner) is nearly cosmopolitan in distribution. Since first reported in Oregon (Harvey, 1876) it has gradually spread throughout the country reaching Florida in 1924 (Wilson, 1934). The larvae are very polyphagous and are important economic pests on many commercial crops grown in Florida including tomatoes, chrysanthemums, gladiolus, sweet corn, ferns, peppers and peanuts.

Difficulties in controlling the beet armyworm with insecticides along with concern for the environment have led entomologists to seek alternate methods of control for this and many other pest insects. These new methods of control require much more information on basic biology and morphology of insects. For example, the work on gametogenesis in the sugarcane borer Diatraea saccharalis

(F.) by Virkki (1963) made possible the radiation and sterilization procedures for the male moths. The biology of the beet armyworm has been studied by Wilson (1932, 1934).

However, no detailed morphological studies of the

insect have been done. The objective of this dissertation






2


is to describe the internal and external morphology of this insect with the aid of the scanning electron microscope with special emphasis on details of the reproductive and external sense organs.














CHAPTER II

LITERATURE REVIEW

Few detailed studies on the morphology and histology of the beet armyworm have been done. The morphology of the female sex pheromone glands of the beet armyworm was described along with 7 other noctuid species: Autographa californica (Speyer), Pseudoplusia includdns (Walker), Rachiplusia ou (Guenee), Feltia subterranea (Fabricius), Heliothis zea (Boddie), Heliothis phloxiphaga (Grote), and Heliothis viresceiis (Fabricius), (Jefferson et al. 1966, 1968). The location of the glands of each species was described and some comparisons were presented. Hammad (1961) described scent glands of different noctuid species: Agrotis ypsilon (Hufnagel), Syngrapha circumflexa (Linnaeus), Earias insulana (Boisduval), Leucania loreyi (Duponchel), Pyrausta (Ostrinia) nubilalis (Hubner), Chilo simplex (Butler), Platyedra gossypiella (Saunders), and S. exigua. He reported S. exigua scent glands belonging to the brush-like type in the 8th abdominal segment.

The external morphology of the antennae of 4 noctuid species: Trichoplusia ni (Hubner), Heliothis zea, S. ornithogalli (Guenece), and S. exigua was described and different types of sensilla were classified but the

3






4


variations among the species were slight (Jefferson et "al. 1970).

These are the only known studies on the beet armyworm, but there are reports on other species of Spodoptera. Most of these are listed under the generic name Prodenia which contained the majority of the species before being synonymized with Spodoptera.

Barth (1961) described the scent glands of S.

ornithogalli and Hammad and Jarczyk (1958) reported on the morphology and histology of scent glands in S. littoralis [as P. litura] a closely related species occurring in Africa and the Middle East.

Many morphological studies have been done on S. litura (Fabricius), an economically important species occurring in India, Southeast Asia and some of the Pacific Islands. Various parts of the nervous system of the adult moths have been described by Srivastava (1967:, 1970) and Mathur (1969). The larval nervous system has been described by Bahadur and Srivastava (1968a, 1968b) and Srivastava (1972). Srivastava and Mathur also described the morphology of the cephalic and prothoracic glands of the mature larva (1963) and the musculature of the head capsule of the mature larva (1964). Jefferson and Rubin (1970) clarified the description of the female sex pheromone gland and Mathur (1968) described the morphology of the excretory system of the larva. Abnormal variations in the wing venation were described by Bhattacherjee and Raghavan (1968).









The morphology and anatomy of the mature larva of S. littoralis [as Prodenia litura] was described by Hassan et al. (1958). Murad (1969) described the musculature of the sucking pump of S. mauritia (Boisduval). The male and female genitalia of S. mauritia acronyctoides (Guenee), S. pecten (Guenee), and S. abyssinia (Boisduval) were described by Chatterjee (1969).

Callahan's work on morphology and histology of

Heliothis zea (1958), was particularly useful and many of his techniques were followed in this study. The morphology of the reproductive systems and mating in two other noctuids Pseudaletia unipuncta (Haworth), and Peridroma margaritosa (Hubner) were compared to Heliothis zea (Callahan and Chapin, 1960). Other detailed morphological descriptions of the reproductive systems of other Lepidoptera include those of Feltia subterranea (F.) (Snow and Callahan, 1968), Ephestia kuhniella (Zeller) (Norris, 1932), Pectinophora gossypiella (Saund) (Wellso and Adkisson, 1962), and Dioryctria abietella (D. & S.) (Fatzinger, 1970). Good histological descriptions havp been given for those of H. zea (Callahan and Cascio, 1963) and E. kuhniella (Musgrave, 1937), and Choristoneura fumiferana (Clemens) (Outram, 1971).

Bullock and Horridge (1965) reviewed the types of

sensilla occurring on insects. Research by Callahan (1969) and his associates (Callahan et al. 1968) described sensilla on the antenna of the corn earworm H. zea moth






6


as well as notes on some other noctuids. However, the only description of the sensilla on the beet armyworm antenna was made by Jefferson et al (1970).

The first microscopic study on the organization of the Lepidoptera wings was by Deschamps (1835). Bowerbank (1838) reported on the scale structure of the wings of Lepidoptera. Wonfor (1869) studied certain butterfly scales and gave some characteristics of sex. The taxonomic value of the scales of the Lepidoptera was reported by Kellogg (1894). Mayer (1896) gave further details on the development of the wing scales and their pigment in butterflies and moths. Kuznetsov (1915) contributed an overall study on Lepidoptera scale structure. Gentil (1935) studied in general the scale arrangement of the wings of Lepidoptera with an optical microscopy method. Since then, some researchers have studied some genera in more detail. The use of the transmission electron microscope on Morpho scales, (Gentil, 1942; Kinder and Suffert, 1943; Richards, 1944), showed that 'iridescent colors were structural and resulted from diffraction of light by ridges on the scale rather than from pigments. Yagi (1954) found that in the genus Colias (Lepidoptera: Pieridae) the yellow and/or orange colors were not structural and disclosed the presence of round and spindle-shaped aggregations of pigments. Kolyer et al (1970) studied the ultrastructure of the scales in Colias eurytheme and he found some variations







7

in color and position. This was the first time the scales were studied with the scanning electron microscope.

Research on the chromosome numbers of Lepidoptera has been done principally on butterflies, with very little work on moths in general and on the Noctuidae in particular. Among the 2,700 species of Noctuidae, the chromosome numbers of only 36 species have been reported (Robinson, 1971). The only member of the genus Spodoptera whose karyotype was determined (Gupta, 1964) was S. litura (as Prodenia litura).














CHAPTER III

METHODS AND MATERIALS

A. Rearing

The male and female moths of the beet armyworm used in this study were obtained from larvae reared on an artificial medium slightly modified (Bacheler and Emmel, 1974) from that used by Shorey and Hale (1965). All developmental stages were held at approximately 27* C and about 87% relative humidity with a 16 hour light and 8 hour dark day length. Larvae were reared in half-pint ice cream containers supplied with enough artificial food to complete larval development. Pupae were sexed and put into separate 1-pint ice cream containers except for those used to maintain the colony. An 8% sucrose solution was continuously available to the adults.


B. Gross Morphological Studies

For the reproductive system studies, two to three day-old male and female moths were dissected in physiological saline. The reproductive system was separated from the digestive tract, examined and photographed. Organs were preserved in alcohol for futher reference.

8






9

Histological studies of 4-day-old virgin moths were made of 3 parts; head-thorax, abdomen and wings. These parts were put into boiling Bouin's fluid, allowed to cool to room temperature for 2 days and then washed in 70% alcohol. Specimens were then imbedded in paraffin. Longitudinal and transverse sections were cut at 6 microns. Sections were stained with Mallory's triple stain method. Histological slides were observed with the Zeiss Photomicroscope II using Nomarski differential interference contrast. Photomicrographs were made of selected sections.

All measurements of wing scales were made with the aid of a micrometer disc in a compound microscope. All dimensions represent an average of measurements made on 12 scales. The measurements of internal reproductive organs were determined by measuring the structure on photographs with a millimeter rule photographed at the same microscope setting.


C. Chromosome Number


Chromosomes were studied in dividing cells in

the testes of larvae of male moths. The testes were taken from the last larval stage and from the male adults 2 to 3 days after emergence. The testes were removed with No. 5 watchmaker forceps and placed on a standard microscope slide. The testes were then macerated and a few drops of lactoaceto-orcein stain (Emmel, 1969) added. This preparation






10


was allowed to stand for about 20 minutes. The stained testes were next covered with a coverslip and the preparation was squashed first by thumb pressure between two pieces of blotting paper and then transferred to a laboratory press to exert uniform pressure and spread the preparation. The perimeter of the coverslip was then sealed with clear lacquer. Mounted slides were stored at 200 F for later reference.

Slides were inspected with a Zeiss Research

Microscope Standard WL fitted with 25X and 40X plan apochromatic flat field objectives and automatic camera, and a Watson photo automatic phase contrast microscope "Hilux 70 PH" fitted with 40X planparo and 90X Fluorite contrast objectives and automatic camera. An oil immersion planapo 100X objective was used for critical observations.

D. Scanning Electron Microscope Studies


Eggs, first instar larva, antenna, wing scales,

and the external reproductive organs of the adults were observed under the scanning electron microscope. Attention was primarily focused on sensory structures. The scanning electron microscope Cambridge Mark II-A was used forthe microstructure of the insect through the courtesy of the USDA in Gainesville and with the aid of Mrs. Thelma C. Carlysle. Range of magnification used was x35 to x14,000.









Insect subjects were mounted on a stub with silver base paint and then introduced into a high vaccum evaporator. The high vaccum evaporator was a Denton DV-502 under a pressure of 2 x 10-5 TORR. Subjects were then coated with 200 angstrom thickness of gold before being transferred to the scanning electron microscope for observation. A camera (Tetronik Corporation 1:1) with polaroid film PN/55 4 x 5 was..attached to the scanning electron microscope.














CHAPTER IV

RESULTS AND DISCUSSION


This research which is basically a descriptive research study is difficult to present in the standard dissertation format. For this reason, this section is subdivided into four sections: adult, egg, larva, and chromosome number.

A. Moth


The beet armyworm moth is about 2.2 cm across the wings (Figure 1, 2). The forewings are mottled grayish and the hindwings are off-white with dark scales along the veins and the border. Males (Figure 1) can usually be distinguished from females (Figure 2) by the more pointed abdomen tip. 1) Antennae


The antennae of the beet armyworm are setiform with

a large number of flagellar segments referred to subsequently as the flagellum whereas the first two segments of the antennae are the scape and pedicel. There is considerable variation in number of segments from specimen to specimen, and even between antennae of a particular specimen. The mean number was 65 segments compared to 63 reported by


12






13
Jefferson et al. 1970. There was little difference in the mean number of segments between the sexes but there was some difference in the length and width of antennal segments between male and female (Table 1). Table 1. Comparison of antennal flagellar segment length
in beet armyworm (n=6 for each sex).

Length (p) Width (p) Females mean range mean range

Proximal
125.3 112-144 164.0 -114-180
segments
Middle
132.8 127-139 100.0 91.108
segments
Distal
Dsee 88.8 84-91 63.2 57-72
segments
Males

Proximal
101.0 91-110 141.6 129-151
segments

Middle
122.7 111-132 114.7 96-140
segments
Distal
77.5 74-86 58.3 50-64 segments


The basal segments of the antennae are short. The

segments elongate distally, reaching their greatest length at about the midpoint of the antenna, then gradually decreasing in length to the end. The diameter of the segments decreases progressively from the base to the end of the antenna. All antenna segments of the male are shorter than the comparable ones of the females (Table 1).

The dorsal surface of the flagellum is covered by

overlapping scales (Figure 3). Two rows of scales oriented






14


diagonally across each segment cover the dorsal surface

-of the antenna. Slightly more than half of the antennal circumference is covered with scales at the base of the antenna. Less of the antennal circumference is covered distally until only about one-third is covered with scales near the tip.

Most sensilla are found on the ventral surface of

the flagellum (Figure 4, 5). At least six distinct kinds of sensilla were recognized. Some of these can be classified into subtypes. All dimensions given are means of 12 measurements (Table 2).

1) Bohm bristles (Figure 7, 8). The Bohm bristles are spine-like sensilla found only on the scape and pedicel. They taper more sharply than the sensilla chaetica of the flagellum. Two types of Bohm bristles occur; more numerous ones are short (type 1) and longer ones (type 2) which are evenly dispersed among type 1 have a socket and sclerotized ring at the base. Bohm bristles are longer in females, their average length varying from 24-39p compared to 17-23p in males.

On the scape, they are concentrated on 4 domes: two large domes laterally, and two small ones, one ventral and one dorsal. On the pedicel, they occur only on two lateral domes near the intersegmental area between the pedicel and the first flagellar segment.

2) Sensilla chaetica (Figure: 6, 9). The sensilla chaetica are blunt spines set in a membraneous socket on the flagellar








segment. A scanning electron micrograph (at 6835X, Figure 11) shows that the surface of the spine is covered with radial ridges or striations.

Sensilla chaetica have a fixed position on both

male and female antennae. Two chaetica are located on the scale side (dorsal) and are the only sensilla occurring there. One chaeticum is always located on each side of the ventral surface at the convergence.point of the scale side with the sensory side. Sensilla chaetica are positioned at about the middle of the length of the segment. Their angle with the segment being about 350. The basal segments have only one chaeticum on the sensory or ventral side. Two chaetica occur on the sensory or ventral surface at approximately the 20th segment making a total of six chaetica per segment.

The longest chaetica on both male and female moths

are located on each side of the antenna at the convergence point of the scale side with the sensory side. The chaetica of the male are longer measuring approximately 108p at the base of the antenna, reaching 132p toward the middle and tapering to 94p at the distal end. Chaetica on the female are 77p at the base of the antenna, 91p near the middle and tapering to 72p at the tip.

Chaetica on the ventral surface of males measure from 77V at the base of the antenna to 89p near the middle and 79p at the tip. The same chaetica on females are 43p, 79p, and 65p respectively. The angle of chaetica on the ventral surface ranges from 450 to 800 on both male and female.






16

The chaetica on the scale or dorsal surface of the antenna are more consistent in length and make a smaller angle in relation to the antennal segment than any of the other chaetica. These chaetica range from 48p long at the base of the antenna to 674 at the tip. The angle is 150 to 350 in relation to an antennal segment. The chaetica originate at the distal end of the first row of scales.

3) Sensilla trichodea. The most numerous sensory hairs

on the antennae can be separated into four types. :a) Type 1: Consists of short porous trichodea having pores arranged in rows. The latter originate dorsally on the sensillum and continue a distally downward orientation to the ventral part of the sensillum (Figure 12). They measure 15-20p in length and 1-2p in diameter at base. Callahan (1969) called them stubby basiconica. b) Type 2: These are long porous trichodea measuring 20-30p in length and 1-2p in diameter at the base. The pore rows originate on the ventral part of the sensillum and extend on both sides of the sensillum in a dorso-distal direction until the two rows converge at the mid-dorsal point (Figure 13, 14). Both types of porous trichodea are thin-walled and are randomly arranged on the sensory side of the antenna. c) Type 3: These are nonporous trichodea (Figure 15). They are thickwalled and measure 38-58p long and 2-5p in diameter at the base. These sensilla are sharply pointed and arranged randomly over the entire sensory surface of both male and female antennae.






17


d) Type 4: These are extremely long trichodea found only

-on the male beet armyworm moth where they are arranged in six rows per segment with 5-6 trichodea per row measuring 84-125p. Three rows originate ventro-laterally on each side of the antenna at the convergence point between the scale side and the sensory side. The long trichodea orient diagonally in rows.

All of the other sensilla types are located between

the rows of long trichodea. Antennal segments bearing the long trichodea rows extend from the base of the antenna to approximately the 40th segment. Sensilla on the remaining segments are comparable to those on the female antenna. Ultrastructure of the nonporous trichodea (type 3) shows a fluted condition arranged circularly (Figure 15)

.4) Sensilla coeloconica (Figure 16). These sensilla

have been referred to as pit peg or picket-fence sensors (Callahan,1969). Each sensillum consists of a porous peg with inward slanting spines oriented circularly around its periphery. Twelve to fifteen spines are arranged in a circular fashion with a fluted peg in the center. Spines curve inward toward the tip of the peg. Diameter of the pit is about 9-10' on both male and female antenna. Pits occur randomly over the sensory surface of antenna with six to ten per segment. Significantly more sensilla were found in the 1st, 2nd, and 25th segments of females and on the 55th and penultimate segments of males (Jefferson et al. 1970).






18

5) Sensilla auricillica. This type of sensillum has

-been called spoon sensor (Griffith, 1968) and shoe-horn sensor (Callahan, 1969), however, sensilla auricillica as used by Jefferson et al. (1970) is more consistent with other latin terms. Sensilla auricillica are earlike or spatula-shaped sensors averaging 12# long and 5S wide on both male and female. The wall is thin and porous with two to four occurring per segment. They are consistently located distally to the chaetica which are located at the convergence point of the sensory side with the scale side of antenna (figure 10, 17).

6) Sensilla styloconica (Figure 18). The sensilla

styloconica are cone-shaped sensory structures mounted at the apices of stout cuticular pegs. Callahan (1969) called them taste rods. There is only one per segment, the size ranging from 16p long on the basal segment to 29U on the distal segment and 7.2p in diameter. They occur at the distal end of each segment in the center of the sensory side.

The functions of all the sensors are not known,

however electrophysiological research by Callahan (1968, 1969) and Jefferson et al (1970) indicate the probable function of some sensors (Table 2).

In both the male and female antennae, the mean total length is 2.1 times greater than the greatest mean width of any segments. The female antennae are longer than the male antennae. This would require that male antennae have more efficient detectors per unit length than the






19

female and consequently might indicate the reason for the multiple rows of trichodea on the male which are much longer than the regular ones, and which apparently serve as pheromone receptors. The great lack of neuroelectrophysiological information makes it impossible to assign reasons for morphological arrangements of the sensilla and consequently one can only conjecture about the placement of certain sensilla on the antennae.


Table 2. Measurements and proposed functions of sensilla
on beet armyworm antenna.

Proposed Diameter Sensilla types function Length i at base

Sensilla coeloconica chemoreceptor 9.6 temp. & humidity

Sensilla auricillica unknown 12 4.8 Sensilla styloconica taste 15.6 7.2 Trichodea types 1, 2 pheromone receiver 17-29 1-2 chemoreceptor

Trichodea type 3 pheromone receiver 38-58 2-5 Trichodea type 4 pheromone receiver 84-125 4-5
(oIonly)

Chaetica ci 55-123 5-10 Chaetica 4 43-91 5-5.5 Bohm bristles 9 24-39 Bohm bristles d 17-23


* n=12

































Figure 1. Beet armyworm moth, male





21





















NY i,


































Figure 2. Beet armyworm moth, female














~r~ '~~~""~;i~"'~ ~":1 a ~i-w~ M xr; r 88" r.
d~~ ~Si~bi~~ N i ~ 61~~ B ~"J aFr~B ii~ai~i" "5 "~11;" $
~ 3,111 1 ~E~E;
r~I S~: ~ ~i' "~ S~i 41 ~B,~
ri:,
r;p
r~ 2~I~ -'1Sb ~ ~ ~' I ~

r
~Fa ~ ~; 4



-~ I i$ii .i411 Zr r;- ss~t
_i
~ 1"

"i;


it;?'~i~
r K~
:.. ~ ~ 88 re" ..~ gs:i~i;~b : ~.





r











rtrs-r






r~

;F~~

"s



\i: tZI


















Figure 3. Dorso-lateral view of antennal segment
showing convergence of scale surface
with sensory surface. Distal portion of antenna with dorsal surface to the
right (X8981
















Figure 4. Lateral view of the ventral surface of
the basal portion of antenna (X705)












Lfn af


















Figure 5. Most distal segment of the antenna
showing sensors covering most of
the circumference (X1410)



















Figure 6. Chaeticum and trichodea on segment
near base of antenna (X2926)





27


















Figure 7. Bohm bristles on scape dome of male
(X900)




















Figure 8. Close-up of Bohm bristles on scape
dome of female (X2667)











CT)


















Figure 9. Close-up of chaeticum on the antenna
(X7182)




















Figure 10. Sensilla auricillica and button-like
sensor (X7049)





31

















Figure 11. Close-up of chaeticum (X6835) Figure 12. Short porous trichodea (X10640)











g ~i )

















Figure 13. Long porous trichodea (X5060) Figure 14. Long porous trichodea (X13,333)





35


















Figure 15. Non-porous trichodea (X6835) Figure 16. Sensilla coeloconica (X6650)





37


















Figure 17. Sensilla auricillica (X6835) Figure 18. Sensilla styloconica (X4430)





39






40

2) Wings

Wings can be differentiated into certain zones based upon the types of scales found there. These zones do not correspond with wing venation. Approximate zones for both sexes and both wings (dorsal and ventral) are shown in Figures 19 and 20. In general the zones are similar on both wings dorsally and ventrally and in.both sexes except for the ventral surface of the forewing which will be discussed later. Zone 1 usually takes up about the anterior one-fourth of each wing and zone 2 takes up the remainder of the wing. The third zone was the border consisting of

3 to 5 rows of scales.

Dorsal forewing: Scales found in zone 1 (Figure 21) of both male and female moths gradually increase in width from the shaft to the tip. They are serrate at the tip with 3 to 6 points in the males and 4 to 6 in the females. Average lengths are 292p and 280p in males and females, respectively. Average width is the same (41p) for both sexes. Pigmentation is more heavily concentrated down the mid-line and the outer margin of the scale and across the apex. The scales in the female are darker than in the male.
There are two types of scales in zone 2. One type is similar to those in zone 1 in that they gradually increase in width from the base to the apex. The length and width of this type scale is 262 x 47p for males -an276.x-.56u for females. Scales are serrate at the tip with 5 to 6






41

points for males and 5 to 7 for females. Heaviest pigmentation is concentrated along the mid-line from the shaft to the distal end of the scale and across the apex.

Interspersed under the serrate scales are the basal scales. These are blunt tipped scales 120 x 45p (males) and 134 x 50p (females). The blunt tip may be indented at 3 or 4 points in the females. There is less pigmentation in these scales than in the serrate scales (Figure 22).

The border scales are confined to 3 to 5 rows on

the outer edge of the wing. These are elongate and the shaft comprises approximately half of the length. The width gradually increases from the shaft to the tip and both shaft and scale are pigmented. Scales are larger in males 610 x 78p with 5 to 9 points compared to 470 x 53p with 4 to 5 points in the female border scales. Width of the shaft is 7.2p for males and only 5.0p for females (Figure 23).
Ventral forewing: There are three zones in both male and female. Zone 1 takes up about one fifth of the wing area and zones 2 and 3 about two fifths each. The only difference between males and females is that zones 1 and 3 are adjacent at the base of the wing in the males while in the female, zone 2 completely separates zones 1 and 3 (Figure 20).

Scales found in zone 1 of both male and female moths gradually increase in width from the shaft to the tip. They are serrate at the tip with 4 to 6 points in the males and 3 to 5 points in the females. Average lengths are 312






42


and 251p in males and females, respectively. Average widths are 56 and 44p respectively (Figure 24).

There are two types of scales in zone 2. One type

is serrate, similar to those in zone 1 with 6 to 7 points for males and 4 to 6 points for females. The length and width of this type scale is 280 x 50p for males and 307 x 49p for females. The second type consists of basal scales which are interspersed under the serrate scales. These scales are shorter and blunt at the tip (Figure 25), with a slight inward taper. Average measurements of these scales are 169 x 52p and 140 x 1S in males and females, respectively.

Covering scales in zone 3 are similar in both males

and females. They are blunt tipped, but there are sometimes indentions in females (Figure 26). The ultrastructure is shown in Figure 28. Measurements are 315 x 55V and 308 x 51p in males and females, respectively. There are blunt basal scales interspersed under the covering scales in males. Their measurements are 96 x 48p There is no evidence of basal scales in females.

There is a sac-like structure (Figure 27) covered with spine-like scales at the posterior base of zone 3 (where the forewing and hindwing are joined). A sexual dimorphism was found with the scales smooth and larger at their base in females (Figure 29) while the scales are stronger and the diameter is about the same for the entire length in males (Figure 30). The function of the sac-like






43

structure is not known but it may minimize friction between the wings and facilitate the movements of both wings.

Dorsal hindwing: There are two zones in both males and females. Zone 1 covers the anterior one-fifth of the hindwing and zone 2 takes up the remainder. The anterior and posterior edges of the hindwing have many piliform (hair-like) scales varying from 600 to 1200p long and

3.5 to 6p wide. Only the males have these piliform scales interspersed in both zones 1 and 2, (Figure 31), there are none in the females in either zone. Covering scales are mostly light gray or white except the scales on the veins have darker pigmentation.

The covering scales in zone 1 are serrate with 2 to 5 points in males and 4 to 6 points in females. Pigmentation in zone 1 is darker than in zone 2. The measurements are 228 x 52p for males and 252 x 58p for females. The basal scales are blunt tipped and interspersed underneath the covering scales. Average measurements are 138 x 50p.

The covering scales in zone 2 are serrate with 2 to 4 points for males and 4 to 6 points for females (Figure 32). Their average measurements are 220 x 55SS (m#a-es and 238 x 53p (females). White scales are predominant. There is no pigmentation in the females compared to a slightly darker pigmentation in the males. Blunt tipped basal scales are interspersed beneath the serrate scales. Their average measurements are 170 x 48 .

The border scales are serrate with 3 to 5 points in the

males and 4 to 5 points in the females. The shaft is one half






44
the total length of the scale. Their length varies from 438 to 860V in males .and 425 to'854 in females. The average width is 40V in males.and 64p in females. The scales are heavily pigmented. The width of the peduncle varies from 4.5 to 6p. The most distinguishing characteristic to separate males from females is the frenulum spine number; there is only one in the males but there are three and sometimes four in the females.

Ventral hindwing: The zonal division is similar to theoneof the dorsal surface. Covering scales in zone 1, are serrate with 4 to 5 points for both sexes (Figure 33). Their measurements are 252 x 48p in males and 225 x 51 in females. The scales are pigmented. The basal scales are blunt tipped and measure 101 x 49p.

All of the scales are white in zone 2. The covering scales are serrate with 3 to 5 points in males and 3 to 4 points in females. Lengths of the scales are much shorter in females compared to those of males 125 to 240V but the width is approximately the same, 50p in males and 53p in females. The basal scales are blunt tipped and interspersed beneath the covering scales. Their measurements are 100 x 1S in males and 103 x 47p in females (Figure 34).

There are four colors of scales: orange, white, gray and black with all variations between the last two. The color is not structural but due to pigment grains inside the scale. The white scales do not contain any pigment. There are no apparent differences at low magnification in form of different colored scales but the upper surface of




























Figure 19. Fore- and hind-wing (dorsal) surface
showing zonal division for both males
and females (zone 1 shaded, zone 2
unshaded).




46






















-12























Figure 20. Upper: zonal division of forewing
(ventral surface) in males

Middle: zonal division of forewing
(ventral surface) in females
Lower: zonal division of hindwing
(ventral surface) in both males and
females





48

















21

S7


















Figure 21. Dorsal forewing scales in zone 1
(X253)




















Figure 22. Dorsal forewing covering and basal
scales in zone 2 (X253)





so50


















Figure 23. Border scales on dorsal forewing (X253)




















Figure 24. Scales on ventral forewing in zone 1
(X253)














N yl










:~ ,, I i ,n
I""
HE II
s
.II pirt
I



r~ 48~ ; s~ '9~ BCE






















i'"






.r;
r




r


















Figure 25. Basal scales and covering scales on
ventral forewing in zone 2 (X253)



















Figure 26. Scales on ventral forewing in zone 3
(X253)






54


















Figure 27. Spine-like scales on posterior base
of ventral forewing on sac-like structure and regular scales in
zone 3 (X226)


















Figure 28. Ultrastructure of scales in zone 3
(X6317)











56












. .. .














14i

















Figure 29. Scales on anterior anal area of the
forewing (female, ventral) (X4522)



















Figure 30. Scales on anterior anal area of the
forewing (male, ventral) (X2660)





58

















Figure 31. Dorsal hindwing: scales in zone 1
and piliform scales (X253)




















Figure 32. Dorsal hindwing: scales in zone 2
(X253)






60


















.... ....

















Figure 33. Ventral hindwing: scales in zone 1
(X253)




















Figure 34. Ventral hindwing: scales in zone 2
(X253)




62

IL

















Figure 35. Ultrastructure of orange scale showing
high longitudinal ribs and circular
cross-ribs (X4985)


















Figure 36. Ultrastructure of gray scale showing
shallow grooves and irregularly
patterned cross-ribs (X5852)







64





































.... ....

















Figure 37. Ultrastructure of scale on ventral
hindwing in zone 2 showing smooth groove
without perforations (X4985)



















Figure 38. Ultrastructure of border scale on
ventral hindwing showing smooth groove
with perforations (X5852)





66


















Figure 39. Ultrastructure of the scale on dorsal
forewing in zone 2 showing straight
cross-ribs (X4985)



















Figure 40. Ultrastructure of scale on dorsal
hindwing in zone 2 showing curved
cross-ribs (X4985)





68































I /'WAR





mom-r








scent ring (Jefferson et al, 1968). There was only one exception in the subfamily Amphipyrinae where the species Spodoptera litura has a glandular epithelium covering the entire 9th abdominal segment.

The scent glands are situated in the non-sclerotized

area, between the 8th and 9th abdominal segments (Figure 41), contrary to Hammad's study on the beet armyworm (1961). A close-up picture of the scent gland (Figure 42) shows clearly glandular cells and the wavy spongy surface of the scent gland (Figure 43). There were different types of scales in the tip of the abdomen area but none of them are glandular scales as described by Hammad. There is no evidence of special secretory ducts in the epithelial cells. The pheromone is supposed to exude through the non-sclerotized area. The diameter of the scent glandular cells is about 10-15p. The wavy surface of the gland area (microvilli) indicates that when the tip of the abdomen is extruded the glandular cells will expand fully through the largest surface and hence, provides the maximum release of pheromone. The location and structure of the scent gland of the beet armyworm is therefore similar to that of Spodoptera ornithogallidescribed by Barth (1961). 4) Reproductive System

a) External genitalia

The genital complex of Lepidopteran females includes the seventh through tenth abdominal segments. The eighth





70:

the orange scales have higher longitudinal ribs and the cross ribs are consistently circular and accentuated when viewed at 4400X (Figure 35). The gray or black scales have relatively smooth, shallow grooves between the ribs and the cross ribs have no regular pattern (Figure 36).

Preliminary research on the ultrastructure of the scales at magnifications in excess of 4000X, revealed differences that offer possibilities for further classification of scale types. There are distinct differences in the structure of the ribs and cross ribs. The groove is smooth without perforations (Figure 37) or with perforations in some scales (Figure 38). The groove in others is perforated with numerous large openings (Figure 39). The cross ribs can be straight (Figure 39) or curved (Figure 40). Another variation is found in border scales on the forewing where every third or fourth rib is thickened. Much more could be done on the subject of ultrastructure of wing scales and a comparative study of various families of moths could reveal some very interesting and meaningful information on relationships throughout the order.


3) Scent Glands

Scent glands are situated in the ventral intersegmental area between the 8th and 9th abdominal segments. They belong to type 2 with ventral sac (Amphipyrinae) compared to type 1 with a dorsal sac or fold (Plusiinae) and type 3 with a





























Figure 41. Scent glands located between VIIIth
and IXth abdominal segments. Dark
color: sclerotized area





72





1/7/th




















.07mm IXth









z, .
ti j7**!*


















Figure 42. The scent gland in the intersegmental
area between the 9th sternite (on the
right) and the 8th sternite (on the
left). Tip of abdomen at top of picture

















Figure 43. Close-up showing wavy surface of the
scent gland and glandular cells underneath. 8th abdominal sternite Visible
on the left. Tip of abdomen at top
of picture





74





A
64














II







abdominal segment of S. exigua is modified with two lateral plates which serve as an ovipostor (Figure 44-46). These plates have three types of sensilla : trichodea, buttonlike, and sensory hairs (Figure 47). Scales are also observed on the inside of the plates (Figure 46).

The male genital complex of Lepidoptera includes the eighth, ninth, and tenth abdominal segment. The external male genitalia in the dorsal view (Figure 48) consists of the gnathos and 3 spine-like structures. The median spine-like structure, common to most Lepidoptera, is the uncus which articulates basally with the tegumen (a structure shaped like a hood or inverted trough lying dorsal of the anus). The paired spines articulate basally with the vinculum which is a U-shaped sclerite derived from the 9th abdominal sternite. Its arms articulate dorsally with the tegumen and its caudal margin with the harpes (or claspers). These two lateral hooks do not occur in some other genera of Noctuidae i.e. Feltia subterranea or Heliothis zea These 3 spines apparently help the male position the female and hold her during copulation (Figure 48). The ventral view (Figure 49), shows the underside of the tegumen and uncus including the scale sockets on the tegumen. In Figure 50, the claspers form a V with the uncus between. The claspers are thickly clothed with scales which may have a sensory function (Figure 51).








Thus the external genitalia of the male consists of

the vinculum which lies ventral to the aedeagus. The left and right arms are actually a single piece forming the sternum of the ninth abdominal segment. The tergal area of the ninth segment, called the tegumen, is fused with the coxosternalarc, the vinculum, to form the base (Figure 49) of the male genitalia. The paired claspers are appendages of the 9th segment and articulate at the coxopodite area of the vinculum. The uncus and aedeagus are structures of the tenth segment. Some of the same sensilla that are found on the antennae are found on the male genitalia: such as chaeticum (Figure 52), and trichodea. The ultrastructure of the scales (Figure 53) shows similar longitudinal ridges and transverse veins as found in the wing scales but without the holes.

The striking difference between the male and female genitalia is that there are many more scales and very few sensilla around the male genitalia compared to the female. Why sensors are much more numerous in the female genitalia is not known, however, it is likely associated with the necessity of the female to locate a suitable oviposition site using the ovipositor as a test organ. b) Reproductive organs


The major morphological difference between reproductive systems of noctuid species are found in the bursa copulatrix and "ovipositor" of the female and in the








claspers or harpes, aedeagus and cuticular portion of the ductus ejaculatorius simplex of the male.

The female reproductive system consists of a pair of ovaries which open to a pair of lateral oviducts (Figure 54). Each ovary is composed of 4 ovarioles (or egg tubes). Ovariole development of the oocytes is panoistic. The maturity of the eggs is indicated by the color: white at the beginning, then pink-purple, and finally greenish when the eggs are mature. The two lateral oviducts join the median oviduct which opens to the gonopore (oviporus and anus) at the 9th segment. Two other glands open to the gonopore:

1) The paired accessory glands consist of small

and long tubules which are enlarged at the

base to function as reservoirs of the accessory

glands and open to a median duct joining the

gonopore.

2) The spermatheca also opens to the gonopore. It

is composed ot three parts:

a) large lobe (utriculus) of spermatheca

b) upper loop of ductus receptaculi (spermathecalduct)

c) convoluted area and lower loop of ductus receptaculi.
There are two ducts at the base of the spermatheca, one opening to the gonopore and the other leading to the base of the bursa copulatrix.

The gonopore which consists of oviporus and anus is on the ninth abdominal segment while the copulatory vulva opens on the eighth abdominal segment.









The bursa copulatrix is the most conspicuous organ in the female insect. The sides are twisted and ridged with sclerotized ribs. At the top of the sac-like organ is the place where the capsules of the spermatophores are formed. The number of spermatophores indicates the number of copulation times. The most spermatophores found in the bursa copulatrix of any moth was four. They accumulate one after another. Williams (1948) listed three classes of Lepidoptera using spermatophores as criteria: class A, having the aperture of the spermatophore in direct contact with the seminal duct, of which the beet armyworm is an example, class B, having a large secretion-filled reservoir between the aperture of the spermatophore and the seminal duct and class C, which includes a few primitive families that have no seminal duct and only one external opening instead of two as is typical of most Lepidoptera. The spermatophore is composed of a capsule and a sclerotized tube or collum (Figure 55). The neck-connection between the capsule and the collum is elbowed making the capsule vertical to the tube. The capsule loses its spheric shape and becomes flattened when the sperm are released through the seminal duct but the collum remains a hard sclerotized structure during the life time of the female.

The adult male reproductive,system has only one

fused testis as compard to two separate testes in the last larval instar. The two large bean-like testes in the









Table 3. Measurements of female internal reproductive
organs and spermatophore.


Organs Mean length (in mm) Accessory glands 5.5 Reservoir of accessory glands .8 Spermatheca (utriculus) 1.2 Spermathecal duct 1.6 Lower loop of ductus receptaculi .6 Bursa copulatrix 3.0 length, 1.2 width Ovarioles 29.1 Vaginal duct 1.5 Seminal duct 1.9 Oviductus communis 2.5 Lateral oviduct 1.8 Spermatophore (Length) (Width)

Capsule 1.2-2.0 1.0-1.3

Neck 1.4-2.0 .2-.3(diameter) Collum 3.0-4.0 .2-.3(diameter)


*n=6



larval stage shrink and fuse in the prepupal stage as the larva shrinks and decreases in size. The moth testis is located around the fourth and fifth abdominal segments. It is spherical and rose-colored. The paired seminal vesicles lead from the testis to the vas deferens which









open into the ductus ejaculatorius duplex near the midpoint (Figure 56). The seminal vesicles are about three-times as wide as the vas deferens. Both are creamywhite like the remaining glands and ducts of the organs. The two accessory glands-as two parallel ducts-are joined together their entire length before they open into the basal end of the ductus ejaculatorius duplex. The latter fuses into the ductus ejaculatorius simplex which is the longest duct of the reproductive organ. About one-sixth of the distance from the beginning, there is an enlargement of the duct. The ductus ejaculatorius simplex leads to the endophallus. The aedeagus is the sclerotized part surrounding the endophallus.


Table 4. Measurements of male internal reproductive
organs.


Organs Mean length (in mm)

Seminal vesicles 1.5 Vas deferens 2.0 Accessory glands 24.0 Ductus ejaculatorius duplex 6.1 Ductus ejaculatorius simplex 51.2 Testis 1.2 (in diameter)




*n=6

















Figure 44. Ovipositor showing sensilla% on
extreme tip (X133)




















Figure 45. Close-up of ovipositor opening (X253)






82









41 rT



















10 1














.





lop Aw a








% l .... ,Vol



.. ...l~ ... !O ai

















Figure 46. Close-up of ovipositor (X525)




















Figure 47. Sensilla on dorsal posterior
ovipositor (X1330)





84












.L


"Ile


















Figure 48. Dorsal view of male genitalia showing
gnathos, uncus, and spines of claspers
(X665)


















Figure 49. Male tegumen supporting uncus with
claspers on either side (X825)






86









vow


















Figure 50. Dorsal view showing uncus and
claspers (X66)




















Figure 51. Inside surface of claspers of male
genitalia (X452)




Full Text
Figure 63. Overall view of anterior portion of
first instar larva (X300)


99


106


109


.79
Table 3. Measurements of female internal reproductive
organs and spermatophore.
Organs Mean length (in mm)
Accessory glands 5.5
Reservoir of accessory glands .8
Spermatheca (utriculus) 1.2
Spermathecal duct 1.6
Lower loop of ductus
receptaculi
.6
Bursa copulatrix
3.0
length, 1.2 width
Ovarioles
29.1
Vaginal duct
1.5
Seminal duct
1.9
Oviductus communis
2.5
Lateral oviduct
1.8
Spermatophore
(Length)
(Width)
Capsule
1.2-2.0
1.0-1.3
i
Neck
1.4-2.0
.2^.3(diameter)
Collum
3.0-4.0
.2-.3(diameter)
*n=6
larval stage shrink and fuse in the
prepupal stage as
the larva shrinks and
decreases in size.
The moth testis
is located around the fourth and fifth abdominal segments.
It is spherical and rose-colored. The paired seminal
vesicles lead from the testis to the vas deferens which




BIOGRAPHICAL SKETCH
Ngo Dong was born October 4, 1937, in Hanoi North
VietNam. In 1961, he received the B.S. from the
University of Hue, South VietNam, and became a teaching
assistant in Zoology of the University of Hue. In 1967,
he was promoted to Chief of the Zoology Laboratory. In
1968, he became Assistant Dean for Student Affairs in
the Faculty of Science. In March 1971, he was sent by
the University of Hue to take higher degrees at the
University of Florida.
From 1971 until the present time he has pursued work
toward the degree of Doctor of Philosophy in Entomology.
On January 11, 1963, Ngo Dong was married to Ton Nu
Thanh Chau and his family now includes four children,
three boys and one girl.
He is a member of the Newell Entomological Society,
the Florida Entomological Society and the Entomological
Society of America.
118;:


I certify that I have read this study and that in
my opinion it conforms to acceptable standards of scholarly
presentation and is fully adequate, in scope and quality,
as a dissertation for the degree of Doctor of Philosophy.
Dale H. Habeck, Chairman
Professor of Entomology
I certify that I have read this study and that in
my opinion it conforms to acceptable standards of scholarly
presentation and is fully adequate, in scope and quality,
as a dissertation for the degree of Doctor of Philosophy.
u
i
0
Harvey ^
Professor
Cromroy
of Entomology
I certify that I have read this study and that in
my opinion it conforms to acceptable standards of scholarly
presentation and is fully adequate, in scope and quality,
as a dissertation for the degree of Doctor of Philosophy.
Milledge Murphey
Professor of Entomology
I certify that I have read this study and that in
my opinion it conforms to acceptable standards of scholarly
presentation and is fully adequate, in scope and quality,
as a dissertation for the degree of Doctor of Philosophy.
C. Kuitert
Professor of Entomology


Figure 15. Non-porous trichodea (X6835)
Figure 16. Sensilla coeloconica (X6650)




iziizig
i i ii 1 1
- 96


Figure 3. Dorso-lateral view of antennal segment
showing convergence of scale surface
with sensory surface. Distal portion
of antenna with dorsal surface to the
right (X898)
Figure 4. Lateral view of the ventral surface of
the basal portion of antenna (X705)


Figure 48. Dorsal view of male genitalia showing
gnathos, uncus, and spines of claspers
(X665)
Figure 49. Male tegumen supporting uncus with
claspers on either side (X825)




Figure 25. Basal scales and covering scales on
ventral forewing in zone 2 (X253)
Figure 26. Scales on ventral forewing in zone 3
(X253)


Figure 13. Long porous trichodea (X5060)
Figure 14. Long porous trichodea (X13,333)


CHAPTER V
CONCLUSIONS
Based on this research the following morphological
distinctions have been determined for the beet armyworm:
1. The female antennae are longer than male
antennae.
2. There are six morphologically distinct types of
sensilla on the antennae of each sex. The male,
however, does have a distinct pattern arrange
ment of the long sensilla trichodea.
3. Wing areas can be divided into distinct zones
based on types of scales.
4. Sexes can be distinguished by the number of
frenulum spines on the hindwing. The male has
one while the female has three and sometimes four.
5. Scent glands are present in the ventral inter-
segmental area between the eighth and ninth
abdominal segments.
6. The female has two .lateral plates on the eighth
abdominal segment which serve as the ovipositor.
Three types of sensilla are found on these plates.
7. The ninth abdominal segment of the male has a
curved uncus and two lateral hooks. These
hooks do not occur in all other noctuid genera.
8. Externally, there are many more scales and very
few sensilla on the male genitalia compared to
the female.
9. The female ovary is composed of four ovarioles.
The distinct bursa copulatrix is described as
well as the spermatophore.
10.The haploid chromosome number for this species
was determined to be n=31.
112


I certify that I have read this study and that in
my opinion it conforms to acceptable standards of scholarly
presentation and is fully adequate, in scope and quality,
as a dissertation for the degree of Doctor of Philosophy.
ames Soule
Professor of Fruit Crops
This dissertation was submitted to the Graduate Faculty
of the College of Agriculture and to the Graduate. Council,
and was accepted as partial fulfillment of the require
ments for the degree of Doctor of Philosophy.
June, 1974
Dean, Graduate School


Figure 50. Dorsal view showing uncus and
claspers (X66)
Figure 51. Inside surface of claspers of male
genitalia (X452)


Figure 31. Dorsal hindwing: scales in zone 1
and piliform scales (X253)
Figure 32. Dorsal hindwing: scales in zone 2
(X253)


A special debt of gratitude is likewise due to
Dr. Le Thanh Minh Chau, Rector of the University of Hue
and Mr. Freddie A. Johnson for their constant help and
encouragement.
Thanks are also due to Mary Davis, Larry Moody, Ed
Sroka, Melinda Chancy and Jo Ann Salter for typing,
illustrating and printing this manuscript.
Last but not least, the author wishes to express
his sincere appreciation to his wife, Ton Nu Thanh Chau,
for the encouragement and understanding she has given
throughout the author's graduate work.
(
iv


MORPHOLOGICAL STUDIES ON THE BEET ARMYWORM
SPODOPTERA EXIGUA (HUBNER) (LEPIDOPTERA: NOCTUIDAE)
By
NGO DONG
A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL
OF THE UNIVERSITY OF FLORIDA
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE
DEGREE OF DOCTOR OF PHILOSOPHY
UNIVERSITY OF FLORIDA
1974


Figure 11. Close-up of chaeticum (X6835)
Figure 12. Short porous trichodea (X10640)


15
segment. A scanning electron micrograph (at 6835X,
Figure 11) shows that the surface of the spine is covered
with radial ridges or striations.
Sensilla chaetica have a fixed position on both
male and female antennae. Two chaetica are located on the
scale side (dorsal) and are the only sensilla occurring
there. One chaeticum is always located on each side of
the ventral surface at the convergence point of the scale
side with the sensory side. Sensilla chaetica are positioned
at about the middle of the length of the segment. Their
angle with the segment being about 35. The basal segments
have only one chaeticum on the sensory or ventral side.
Two chaetica occur on the sensory or ventral surface at
approximately the 20th segment making a total of six
chaetica per segment.
The longest chaetica on both male and female moths
are located on each side of the antenna at the convergence
point of the scale side with the sensory side. The chaetica
of the male are longer measuring approximately 108y at the
base of the antenna, reaching 132y toward the middle and
tapering to 94y at the distal end. Chaetica on the female
are 77y at the base of the antenna, 91y near the middle and
tapering to 72y at the tip.
Chaetica on the ventral surface of males measure from
77y at the base of the antenna to 89y near the middle and
79y at the tip. The same chaetica on females are 43y, 79y,
and 65y respectively. The angle of chaetica on the ventral
surface ranges from 45 to 80 on both male and female.


LITERATURE CITED
Bacheler, J.S. and T. C. Emmel. 1974. Genetic control of
maculation and hindwing color in Apantesis phalerata
(Arctiidae). J. Res. Lepidoptera: in press.
Bahadur, J., and B. B. L. Srivastava. 1968a. Studies on
the nervous tracts in the brain of the larva of
Prodenia litura Fabr. (Lepidoptera: Noctuidae).
Acta. ZOOL. (Stockholm 49 (1/2) : 163-75.
1968b. The nerves of the thoracic segments of
the larva of Prodenia litura Fabr. (Lepidoptera:
Noctuidae). J.N.Y. Entomol. Soc. 74(4): 168-79.
Barth, R. 1961. Die Druesenorgane des Weichens von Prodenia
ornithogalli Guenee (Lepidoptera: Noctuidae).
Ann. Acad. Brasil Cienc. 33: 429-33.
Bhattacherjee, N. S. and M. V. Raghavan. 1968. Some
abnormal variation in the wing venation of Prodenia
litura Fabr. (Lepidoptera: Noctuidae). Indian J.
Entomol. 29(1): 98-99.
Bowerbank, J. 1838. On the structure of the scales on the
wings of Lepidopterous insects. Entomol. Mag. p. 300-4.
Bullock, T. H. and G. A. Horridge. Structure and function
in the nervous systems of invertebrates. W. H.
Freemar and Co. San Francisco and London. 1965.
1719 p.
Callahan, P. S. 1958. Serial morphology as a technique for
determination of reproductive patterns in the corn
earworm, Heliothis zea (Boddie). Ann. Entomol. Soc.
Amer. 51(5): 413-28.
1969. The exoskeleton of the corn earworm,
Heliothis zea (Lepidoptera: Noctuidae) with special
reference to the sensilla as polytubular dielectric
arrays. University Georgia Coll. Agr. Exp. Sta.
Res. Bull. 54: 1-105.
> and Joan B. Chapin. 1960. Morphology of the
reproductive systems and mating in two representative
members of the family Noctuidae, Pseudaletia unipuncta
and Peridroma margaritosa, with comparisons to
Heliothis zea. Ann. Entomol. Soc. Amer. 53(6): 763-82.
113


11
Insect subjects were mounted on a stub with silver base
paint and then introduced into a high vaccum evaporator.
The high vaccum evaporator was a Denton DV-502 under a
pressure of 2 x 105 TORR. Subjects were then coated
with 200 angstrom thickness of gold before being trans
ferred to the scanning electron microscope for observa
tion. A camera (Tetronik Corporation 1:1) with polaroid
film PN/55 4 x 5 was.attached to the scanning electron
microscope.
t


MORPHOLOGICAL STUDIES ON THE BEET ARMYWORM
SPODOPTERA EXIGUA (HUBNER) (LEPIDOPTERA: NOCTUIDAE)
By
NGO DONG
A DISSERTATION PRESENTED TO THE GRADUATE COUNCIL
OF THE UNIVERSITY OF FLORIDA
IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE
DEGREE OF DOCTOR OF PHILOSOPHY
UNIVERSITY OF FLORIDA
1974

To my wife, Ton-Nu Thanh-Chau
and my children,
Ngo Bao, Ngo Quynh, Ngo Anh, Ngo Anh-Thu.

ACKNOWLEDGMENTS
The author is greatly indebted to Dr. Dale H. Habeck
as chairman of the Supervisory Committee for his guidance,
criticisms, and valuable suggestions in carrying out the
work and organizing the material for this dissertation.
Further appreciation is expressed to Dr. Habeck for
supplying the laboratory and photographic supplies necessary
for this research.
Deep appreciation is expressed to Dr. Harvey L.
Cromroy, Departments of Entomology and Radiation Biophysics,
who has offered valuable assistance to the author.
The author wishes to express his gratitude to Mrs.
Thelma C. Carlysle for her aid with the use of the scanning
electron microscope, darkroom work, and the histological
slides. Grateful acknowledgment is given to Dr. Derrell
Chambers for providing facilities in the Insect Attractants,
Behavior and Basic Biology Research Laboratory, USDA,
Gainesville, and to Dr. Thomas C. Emmel for helping in the
chromosome study.
Special thanks are extended to Dr. Dale Habeck, Dr.
Harvey Cromroy, Dr. Milledge Murphey, Dr. Louis C. Kuitert
and Dr. James Soule who have taken the time to edit and
criticize this dissertation.
ii i

A special debt of gratitude is likewise due to
Dr. Le Thanh Minh Chau, Rector of the University of Hue
and Mr. Freddie A. Johnson for their constant help and
encouragement.
Thanks are also due to Mary Davis, Larry Moody, Ed
Sroka, Melinda Chancy and Jo Ann Salter for typing,
illustrating and printing this manuscript.
Last but not least, the author wishes to express
his sincere appreciation to his wife, Ton Nu Thanh Chau,
for the encouragement and understanding she has given
throughout the author's graduate work.
(
iv

TABLE OF CONTENTS
ACKNOWLEDGMENTS iii.
LIST OF TABLES vi
LIST OF FIGURES vii
ABSTRACT xii
CHAPTER
I. INTRODUCTION 1
II. LITERATURE REVIEW 3
III.METHODS AND MATERIALS 8
A. Rearing 8
B. Gross Morphological Studies 8
C. Chromosome Number 9
D. Scanning Electron Microscope 10
IV. RESULTS AND DISCUSSION 12
A. Moth 12
1) Antennae 12
2) Wings 40
3) Scent Glands 69
4) Reproductive System 70
B. Egg 97
C. Larva 97
D. Chromosome Number 102
V. CONCLUSIONS 112
VI. LITERATURE CITED llo
VII. BIOGRAPHICAL SKETCH 118
v

LIST OF TABLES
Table 1. Comparison of antennal flagellar
segment length in beet armyworm 13
Table 2. Measurements and proposed functions
of sensilla on beet armyworm antenna. 19
Table 3. Measurements of female internal
reproductive organs and spermatophore 79
Table 4. Measurements of male internal
reproductive organs 80
vi

ft
LIST OF FIGURES
Figure 1. Beet armyworm moth, male 21
Figure 2. Beet armyworm moth, female 23
Figure 3. Dorso-lateral view of antennal
segment showing convergence of
scale surface with sensory sur
face. Distal portion of antenna
with dorsal surface to the right
(X898) 25
Figure 4. Lateral view of the ventral
surface of the basal portion
of antenna (X7 05) 25
Figure 5. Most distal segment of the antenna
showing sensors covering most of
the circumference (X1410) 27
Figure 6. Chaeticum and trichodea on segment
near base of antenna (X2926) 27
Figure 7. Bohm bristles on scape dome of male
(X900) 2.9
Figure 8. Close-up of Bohm bristles on scape
dome of female (X2667) 29
Figure 9. Close-up of chaeticum on the antenna
(X7182) 31
Figure 10. Sensilla auricillica and button-like
sensor (X7049) 31
Figure 11. Close-up of chaeticum (X6835) 33
Figure 12. Short porous trichodea (X1540) ... 33
Figure 13. Long porous trichodea (X5060) 35
Figure 14. Long porous trichodea (X13,333) 35
Figure 15. Non-porous trichodea (X6835) 37
Vll

LIST OF FIGURES (Continued)
Figure 16.
Sensilla coeloconica (X6650) 37
Figure 17.
Sensilla auricillica (X6835) 39
Figure 18.
Sensilla styloconica (X4430) 39
Figure 19.
Fore- and hind-wing (dorsal) sur-
face showing zonal division for
both males and females (zone 1
shaded, zone 2 unshaded) 46
Figure 20.
Upper: zonal division of forewing
(ventral surface) in males
Middle: zonal division of forewing
(ventral surface) in females
Lower: zonal division of hindwing
(ventral surface in both males
and females 48
Figure 21.
Dorsal forewing scales in zone 1
(X253) 50
Figure 22.
Dorsal forewing covering and basal
scales in zone 2 (X253) 50
Figure 23.
Border scales on dorsal forewing
(X253) 52
Figure 24.
Scales on ventral forewing in zone 1
(X253) 5:2
Figure 25.
Basal scales and covering scales on
ventral forewing in zone 2 (X253). ... 54
Figure 26.
Scales on ventral forewing in zone 3
(X253) 54
Figure 27.
Spine-like scales on posterior base
of ventral forewing on sac-like
structure and regular scales in
zone 3 (X226) 56
Figure 28.
Ultrastructure of scales in zone 3
(X6317) / 56
Figure 29.
Scales on anterior anal area of the
forewing (female, ventral) (X4522) ... 58
Figure 30.
Scales on anterior anal area of the
forewing (male, ventral ) (X2660) ... 58
viii
. 58

LIST OF FIGURES (Continued)
Figure
31.
Dorsal hindwing: scales in zone
1 and piliform scales (X253) ....
. 60
Figure
32.
Dorsal hindwing: scales in zone
2 (X253)
. 60
Figure
33.
Ventral hindwing: scales in zone
1 (X253)
. 62
Figure
34.
Ventral hindwing: scales in zone
2 (X253)
. 62
Figure
35.
Ultrastructure of orange scale
showing high longitudinal ribs
and circular cross-ribs (X4985) .
. 64
Figure
36.
Ultrastructure of gray scale showing
shallow grooves and irregularly
patterned cross-ribs (X5852) ....
. 64
Figure
37.
Ultrastructure of scale on ventral
hindwing in zone 2 showing smooth
groove without perforations (X4985)
. 66
Figure
38.
Ultrastructure of border scale on
ventral hindwing showing smooth
groove with perforations (X5852) .
. 66
Figure
39.
Ultrastructure of the scale on dorsal
forewing in zone 2 showing straight
cross-ribs (X4985)
. 68
Figure
40.
Ultrastructure of scale on dorsal
hindwing in zone 2 showing curved
cross-ribs (X4985) .
. 68
Figure
41.
Scent glands located between VUIth
and IXth abdominal segments. Dark
color: sclerotized area
. 72
Figure
42.
The scent gland in the intersegmental
area between the 9th sternite and
the 8th sternite ,
Figure
43.
Close-up showing wavy surface of
the scent gland and glandular
cells underneath
Figure
44.
Ovipositor showing sensilla on extreme
tip (X133)
IX

LIST OF FIGURES (Continued)
Figure 45. Close-up of ovipositor opening
(X253) 82
Figure 46. Close-up of ovipositor (X253) 84
Figure 47. Sensilla on dorsal posterior
ovipositor (X1330) 84
Figure 48. Dorsal view of male genitalia
(X665) 86
Figure 49. Male tegumen supporting uncus with
claspers on either side (X825) 86
Figure 50. Dorsal view showing uncus and
claspers (X66) 88
Figure 51. Inside surface of claspers of
male genitalia (X452) 88
Figure 52. Sensilla and scales on outside
of the clasper; male genitalia (X1465) .90
Figure 53. Ultrastructure of scale inside of
clasper; male genitalia (X7182) 90
Figure 54. The female reproductive system 92
Figure 55. The Spermatophore 94
Figure 56. The male reproductive system 96
Figure 57. Beet armyworm eggs partly covered
with scales from tip of female
abdomen (X133) 99
Figure 58. Apex of egg showing micropyle and
chorion design (X931) 99
Figure 59. Egg surface showing aeropyles (pores)
on edge of ridges (X1430) 101
Figure 60. Ocelli and antenna of first instar
larva, dorso lateral view (X665) .... 101
Figure 61. Microspines and setae on first
instar larva (XI596) 10.4
Figure 62. Spiracle of first instar larva
(1410) 104
Figure 63. Overall view of anterior portion of
first instar larva (X300) 106
x

LIST OF FIGURES (Continued)
Figure 64. Chromosomes of the beet armyworm
observed under microscope with
phase (n=31) (X1197) 109
Figure 65. Chromosomes of the beet armyworm
observed under microscope without
phase (X1197) 109
Figure 66. Bundles of sperms in testis (X1197) HI
Figure 67. Two sperms among nucleus division
in testis (X1197) Ill
xx

Abstract of Dissertation Presented to the
Graduate Council of the University of Florida
in Partial Fulfillment of the Requirements for the
Degree of Doctor of Philosophy
MORPHOLOGICAL STUDIES ON THE BEET ARMYWORM
SPODOPTERA EXIGUA (HUBNER) (LEPIDOPTERA: NOCTUIDAE)
By
Ngo Dong
June, 1974
Chairman: Dale H. Habeck
Major Department: Entomology and Nematology
The beet armyworm Spodoptera exigua (Hubner)
(Lepidoptera: Noctuidae), a nearly cosmopolitan species,
is an economically important pest in Florida and other areas.
Morphological studies were concentrated on the antenna, wing
scales, and the external genitalia and reproductive system
of the adult, the egg, and first instar larva.
Female antennae are longer than male antennae. Six
morphologically distinct types of sensilla were found on
the antennae of each sex: Bohm bristles, chaetica,
trichodea, auricillica, styloconica and coeloconica.
However, only the male has the long sensilla trichodea.
These are arranged in a distinct pattern. Wings can be
divided into distinct zones based on types of scales:
XI1

two zones in forewing (dorsal), hindwing (dorsal and
ventral), and three zones in forewing (ventral). Scent
glands are present in the ventral intersegmental area
between the 8th and 9th abdominal segments. Three types
of sensilla are found on the lateral plates forming
the ovipositor. The 9th abdominal segment of the male
has a curved uncus and two lateral hooks arising from
the claspers. Externally, there are many more scales
and very few sensilla on the male genitalia compared
to the female. The female ovary is composed of four
ovarioles and development is panoistic.
The egg chorion around the micropyle is shaped
petal-like with 7-11 lobes. Many tiny aeropyles occur
on the edge of egg ridges.
The first instar larva is covered with microspines.
Head setae tend to be sharp, curved and without raised
pinaculum while body setae are straight and blunt tipped
with pinaculum.
The haploid chromosome number for this species was
determined to be n=31.
XI 3 i

CHAPTER I
INTRODUCTION
The beet armyworm Spodoptera exigua (Hubner) is
nearly cosmopolitan in distribution. Since first re
ported in Oregon (Harvey, 1876) it has gradually spread
throughout the country reaching Florida in 1924 (Wilson,
1934). The larvae are very polyphagous and are important
economic pests on many commercial crops grown in Florida
including tomatoes, chrysanthemums, gladiolus, sweet
corn, ferns, peppers and peanuts.
Difficulties in controlling the beet armyworm with
insecticides along with concern for the environment have
led entomologists to seek alternate methods of control
for this and many other pest insects. These new methods
of control require much more information on basic biology
and morphology of insects. For example, the work on
gametogenesis in the sugarcane borer Diatraea saccharalis
(F.) by Virkki (1963) made possible the radiation and
sterilization procedures for the male moths. The biology
of the beet armyworm has been studied by Wilson (1932, 1934).
However, no detailed morphological studies of the
insect have been done. The objective of this dissertation

2
is to describe the internal and external morphology of
this insect with the aid of the scanning electron micro
scope with special emphasis on details of the reproduc
tive and external sense organs.

CHAPTER II
LITERATURE REVIEW
Few detailed studies on the morphology and histology
of the beet armyworm have been done. The morphology of
the female sex pheromone glands of the beet armyworm was
described along with 7 other noctuid species: Autographa
californica (Speyer), Pseudoplusia includns (Walker),
Rachiplusia ou (Guenee), Feltia subterrnea (Fabricius) ,
Heliothis zea (Boddie), Heliothis phloxiphaga (Grote),
and Heliothis virescens (Fabricius), (Jefferson et al.
1966, 1968). The location of the glands of each species
was described and some comparisons were presented. Hammad
(1961) described scent glands of different noctuid species
Agrotis ypsilon (Hufnagel), Syngrapha circumflexa
(Linnaeus), Earias insulana (Boisduval), Leucania
loreyi (Duponchel), Pyrausta (Ostrinia) nubilalis (Hubner)
Chilo simplex (Butler), Platyedra. gossypiella (Saunders),
and S. exigua. He reported S. exigua scent glands belong
ing to the brush-like type in the 8th abdominal segment.
The external morphology of the antennae of 4 noctuid
species: Trichoplusia ni (Hubner), Heliothis zea, S.
ornithogalli (Guenee), and S. exigua was described and
different types of sensilla were classified but the
3

4

variations among the species were slight (Jefferson et
al. 1970).
These are the only known studies on the beet army-
worm, but there are reports on other species of Spodoptera.
Most of these are listed under the generic name Prodenia
which contained the majority of the species before being
synonymized with Spodoptera.
Barth (1961) described the scent glands of S.
ornithogalli and Hammad and Jarczyk (1958) reported on the
morphology and histology of scent glands in S. littoralis
[as P. litura] a closely related species occurring in
Africa and the Middle East.
Many morphological studies have been done on S.
litura (Fabricius), an economically important species
occurring in India, Southeast Asia and some of the Pacific
Islands. Various parts of the nervous system of the
adult moths have been described by Srivastava (1967,
4
1970) and Mathur (1969). The larval nervous system has
been described by Bahadur and Srivastava (1968a, 1968b)
and Srivastava (1972). Srivastava and Mathur also
described the morphology of the cephalic and prothoracic
glands of the mature larva (1963) and the musculature of
the head capsule of the mature larva (1964). Jefferson
and Rubin (1970) clarified the description of the female
sex pheromone gland and Mathur (1968) described the
morphology of the excretory system of the larva. Abnormal
variations in the wing venation were described by
Bhattacherjee and Raghavan (1968).

5
The morphology and anatomy of the mature larva of
S. littoralis [as Prodenia litura] was described by
Hassan et al. (1958). Murad (1969) described the
musculature of the sucking pump of S. mauritia (Boisduval).
The male and female genitalia of S. mauritia acronyctoides
(Guenee), S. pecten (Guenee), and S. abyssinia (Boisduval)
were described by Chatterjee (1969).
Callahan's work on morphology and histology of
Heliothis zea (1958), was particularly useful and many
of his techniques were followed in this study. The
morphology of the reproductive systems and mating in two
other noctuids Pseudaletia unipuncta (Haworth), and
Peridroma margaritosa (Hubner) were compared to Heliothis
zea (Callahan and Chapin, 1960). Other detailed morpho
logical descriptions of the reproductive systems of other
Lepidoptera include those of Feltia subterrnea (F.)
(Snow and Callahan, 1968), Ephestia kuhniella (Zeller)
(Norris, 1932), Pectinophora gossypiella (Saund.) (Wellso
and Adkisson, 1962), and Dioryctria abietella (D. 8 S.)
(Fatzinger, 1970). Good histological descriptions have
been given for those of H. zea (Callahan and Cascio, 1963)
and E. kuhniella (Musgrave, 1937), and Choristoneura
fumiferana (Clemens) (Outram, 1971).
Bullock and Horridge (1965) reviewed the types of
sensilla occurring on insects. Research by Callahan (1969)
and his associates (Callahan et al. 1968) described
sensilla on the antenna of the corn earworm H. zea moth

6
as well as notes on some other noctuids. However,
the only description of the sensilla on the beet
armyworm antenna was made by Jefferson et al (1970).
The first microscopic study on the organization
of the Lepidoptera wings was by Deschamps (1835) .
Bowerbank (1838) reported on the scale structure of
the wings of Lepidoptera. Wonfor (1869) studied certain
butterfly scales and gave some characteristics of sex.
The taxonomic value of the scales of the Lepidoptera
*
was reported by Kellogg (1894). Mayer (1896) gave
further details on the development of the wing scales
and their pigment in butterflies and moths. Kuznetsov
(1915) contributed an overall study on Lepidoptera scale
structure. Gentil (1935) studied in general the scale
arrangement of the wings of Lepidoptera with an optical
microscopy method. Since then, some researchers have
studied some genera in more detail. The use of the
transmission electron microscope on Morpho scales, (Gentil,
1942; Kinder and Suffert, 1943; Richards, 1944), showed
that ..iridescent colors were structural and resulted
from diffraction of light by ridges on the scale rather
than from pigments. Yagi (1954) found that in the genus
Colias (Lepidoptera: Pieridae) the yellow and/or orange
colors were not structural and disclosed the presence of
round and spindle-shaped aggregations of pigments.
Kolyer et al (1970) studied the ultrastructure of the
scales in Colias eurytheme and he found some variations

7
in color and position. This was the first time the
scales were studied with the scanning electron micro
scope .
Research on the chromosome numbers of Lepidoptera
has been done principally on butterflies, with very
little work on moths in general and on the Noctuidae
in particular. Among the 2,700 species of Noctuidae,
the chromosome numbers of only 36 species have been
reported (Robinson, 1971). The only member of the
genus Spodoptera whose karyotype was determined (Gupta,
1964) was S. litura (as Prodenia litura).

CHAPTER III
METHODS AND MATERIALS
A. Rearing
The male and female moths of the beet armyworm used
in this study were obtained from larvae reared on an
artificial medium slightly modified (Bacheler and Emmel,
1974) from that used by Shorey and Hale (1965). All
developmental stages were held at approximately 27 C
and about 871 relative humidity with a 16 hour light
and 8 hour dark day length. Larvae were reared in
half-pint ice cream containers supplied with enough
artificial food to complete larval development. Pupae
were sexed and put into separate 1-pint ice cream
containers except for those used to maintain the colony.
An 8% sucrose solution was continuously available to the
adults.
B. Gross Morphological Studies
For the reproductive system studies, two to three
day-old male and female moths were dissected in phy
siological saline. The reproductive system was separated
from the digestive tract, examined and photographed.
Organs were preserved in alcohol for futher reference.
8

9
Histological studies of 4-day-old virgin moths were
made of 3 parts; head-thorax, abdomen and wings. These
parts were put into boiling Bouin's fluid, allowed to
cool to room temperature for 2 days and then washed in
701 alcohol. Specimens were then imbedded in paraffin.
Longitudinal and transverse sections were cut at 6 microns.
Sections were stained with Mallorys triple stain method.
Histological slides were observed with the Zeiss Photo
microscope II using Nomarski differential interference
contrast. Photomicrographs were made of selected sections.
All measurements of wing scales were made with the
aid of a micrometer disc in a compound microscope. All
dimensions represent an average of measurements made on
12 scales. The measurements of internal reproductive
organs were determined by measuring the structure on
photographs with a millimeter rule photographed at the
same microscope setting.
C. Chromosome Number
Chromosomes were studied in dividing cells in
the testes of larvae of male moths. The testes were taken
from the last larval stage and from the male adults 2 to 3 days
after emergence. The te.stes were removed with No. 5 watch
maker forceps and placed on a standard microscope slide.
The testes were then macerated and a few drops of lacto-
aceto-oreein stain (Emmel, 1969) added. This preparation

10
was allowed to stand for about 20 minutes. The stained
testes were next covered with a coverslip and the pre
paration was squashed first by thumb pressure between
two pieces of blotting paper and then transferred to a

laboratory press to exert uniform pressure and spread
the preparation. The perimeter of the coverslip was
then sealed with clear lacquer. Mounted slides were
stored at 20 F for later reference.
Slides were inspected with a Zeiss Research
Microscope Standard WL fitted with 25X and 40X plan
apochromatic flat field objectives and automatic
camera, and a Watson photo automatic phase contrast
microscope "Hilux 70 PH" fitted with 40X planparo and
90X Fluorite contrast objectives and automatic camera.
An oil immersion planapo 100X objective was used for
critical observations.
D. Scanning Electron Microscope Studies
Eggs, first instar larva, antenna, wing scales,
and the external reproductive organs of the adults were
observed under the scanning electron microscope. Attention
was primarily focused on sensory structures. The scanning
electron microscope Cambridge Mark Il-A was used for the
microstructure of the insect through the courtesy of the
USDA in Gainesville and with the aid of Mrs. Thelma C.
Carlysle. Range of magnification used was x35 to xl4,000.

11
Insect subjects were mounted on a stub with silver base
paint and then introduced into a high vaccum evaporator.
The high vaccum evaporator was a Denton DV-502 under a
pressure of 2 x 105 TORR. Subjects were then coated
with 200 angstrom thickness of gold before being trans
ferred to the scanning electron microscope for observa
tion. A camera (Tetronik Corporation 1:1) with polaroid
film PN/55 4 x 5 was.attached to the scanning electron
microscope.
t

CHAPTER IV
RESULTS AND DISCUSSION
This research which is basically a descriptive research
study is difficult to present in the standard dissertation
format. For this reason, this section is subdivided into
four sections: adult, egg, larva, and chromosome number.
A. Moth
The beet armyworm moth is about 2.2 cm across the wings
(Figure 1, 2). The forewings are mottled grayish and the
hindwings are off-white with dark scales along the veins and
the border. Males (Figure 1) can usually be distinguished
from females (Figure 2) by the more pointed abdomen tip.
1) Antennae
The antennae of the beet armyworm are setiform with
a large number of flagellar segments referred to subsequently
as the flagellum whereas the first two segments of the
antennae are the scape and pedicel. There is considerable
variation in number of segments from specimen to specimen,
and even between antennae of a particular specimen. The
mean number was 65 segments compared to 63 reported by
12

13
Jefferson et al. 1970. There was little difference in
the mean number of segments between the sexes but there
was some difference in the length and width of antennal
segments between male and female (Table 1).
Table 1. Comparison of antennal flagellar segment length
in beet armyworm (n=6 for each sex).
Length (y) Width (y)
Females
mean
range
mean
range
Proximal
segments
125.3
112-144
164.0
-114-180
Middle
segments
132.8
127-139
100.0
91.108
Distal
segments
88.8
84-91
63.2
57-72
Males
-
Proximal
segments
101.0
91-110
141.6
129-151
Middle
segments
122.7
111-132
114.7
96-140
Distal
segments
77.5
74-86
58.3
50-64
The basal segments of the antennae are short. The
segments elongate distally, reaching their greatest length
at about the midpoint of the antenna, then gradually de
creasing in length to the end. The diameter of the seg-
\
ments decreases progressively from the base to the end of
the antenna. All antennal segments of the male are shorter
than the comparable ones of the females (Table 1).
The dorsal surface of the flagellum is covered by
overlapping scales (Figure 3). Two rows of scales oriented

14
diagonally across each segment cover the dorsal surface
-of the antenna. Slightly more than half of the antennal
circumference is covered with scales at the base of the
antenna. Less of the antennal circumference is covered
distally until only about one-third is covered with scales
near the tip.
Most sensilla are found on the ventral surface of
the flagellum (Figure 4, 5). At least six distinct kinds
of sensilla were recognized. Some of these can be clas
sified into subtypes. All dimensions given are means of
12 measurements (Table 2).
1) Bohm bristles (Figure 7, 8). The Bohm bristles are
spine-like sensilla found only on the scape and pedicel.
They taper more sharply than the sensilla chaetica of the
flagellum. Two types of Bohm bristles occur; more numerous
ones are short (type 1) and longer ones (type 2) which are
evenly dispersed among type 1 have a socket and sclerotized
ring at the base. Bohm bristles are longer in females,
their average length varying from 24-39y compared to 17-23y
in males.
On the scape, they are concentrated on 4 domes: two
large domes laterally, and two small ones, one ventral and
one dorsal. On the pedicel, they occur only on two lateral
domes near the intersegmental area between the pedicel and
the first flagellar segment.
2) Sensilla chaetica (Figure 6, 9). The sensilla chaetica
are blunt spines set in a membraneous socket on the flagellar

15
segment. A scanning electron micrograph (at 6835X,
Figure 11) shows that the surface of the spine is covered
with radial ridges or striations.
Sensilla chaetica have a fixed position on both
male and female antennae. Two chaetica are located on the
scale side (dorsal) and are the only sensilla occurring
there. One chaeticum is always located on each side of
the ventral surface at the convergence point of the scale
side with the sensory side. Sensilla chaetica are positioned
at about the middle of the length of the segment. Their
angle with the segment being about 35. The basal segments
have only one chaeticum on the sensory or ventral side.
Two chaetica occur on the sensory or ventral surface at
approximately the 20th segment making a total of six
chaetica per segment.
The longest chaetica on both male and female moths
are located on each side of the antenna at the convergence
point of the scale side with the sensory side. The chaetica
of the male are longer measuring approximately 108y at the
base of the antenna, reaching 132y toward the middle and
tapering to 94y at the distal end. Chaetica on the female
are 77y at the base of the antenna, 91y near the middle and
tapering to 72y at the tip.
Chaetica on the ventral surface of males measure from
77y at the base of the antenna to 89y near the middle and
79y at the tip. The same chaetica on females are 43y, 79y,
and 65y respectively. The angle of chaetica on the ventral
surface ranges from 45 to 80 on both male and female.

16
The chaetica on the scale or dorsal surface of the
antenna are more consistent in length and make a smaller
angle in relation to the antennal segment than any of the
other chaetica. These chaetica range from 48y long at
the base of the antenna to 67y at the tip. The angle is
/
15 to 35 in relation to an antennal segment. The
chaetica originate at the distal end of the first row of
scales.
3) Sensilla trichodea. The most numerous sensory hairs
on the antennae can be separated into four types. !a) Type 1
Consists of short porous trichodea having pores arranged in
rows. The latter originate dorsally on the sensillum and
continue a distally downward orientation to the ventral
part of the sensillum (Figure 12). They measure 15-20y
in length and l-2y in diameter at base. Callahan (1969)
called them stubby basiconica. b) Type 2: These are long
porous trichodea measuring 20-30y in length and l-2y in
diameter at the base. The pore rows originate on the
ventral part of the sensillum and extend on both sides of
the sensillum in a dorso-distal direction until the two
rows converge at the mid-dorsal point (Figure 13, 14). Both
types of porous trichodea are thin-walled and are randomly
arranged on the sensory side of the antenna. c) Type 3:
These are nonporous trichodea (Figure 15). They are thick-
walled and measure 38-58y long and 2-5y in diameter at the
base. These sensilla are sharply pointed and arranged
randomly over the entire sensory surface of both male and
female antennae.

17
d) Type 4: These are extremely long trichodea found only
on the male beet armyworm moth where they are arranged in
six rows per segment with 5-6 trichodea per row measuring
84-125p. Three rows originate ventro-laterally on each
side of the antenna at the convergence point between the
scale side and the sensory side. The long trichodea
orient diagonally in rows.
All of the other sensilla types are located between
the rows of long trichodea. Antennal segments bearing the
long trichodea rows extend from the base of the antenna
to approximately the 40th segment. Sensilla on the re
maining segments are comparable to those on the female
antenna. Ultrastructure of the nonporous trichodea (type 3)
shows a fluted condition arranged circularly (Figure 15)
4) Sensilla coeloconica (Figure 16). These sensilla
have been referred to as pit peg or picket-fence sensors
(Callahan, 1969). Each sensillum consists of a porous peg
with inward slanting spines oriented circularly around its
periphery. Twelve to fifteen spines are arranged in a
circular fashion with a fluted peg in the center. Spines
curve inward toward the tip of the peg. Diameter of the
pit is about 9-10y on both male and female antenna. Pits
occur randomly over the sensory surface of antenna with
six to ten per segment. Significantly more sensilla were
found in the 1st, 2nd, and 25th segments of females and
on the 55th and penultimate segments of males (Jefferson
et al. 1970).

18
5) Sensilla auricillica. This type of sensillum has
been called spoon sensor (Griffith, 1968) and shoe-horn
sensor (Callahan, 1969), however, sensilla auricillica
as used by Jefferson et al. (1970) is more consistent
with other latin terms. Sensilla auricillica are ear
like or spatula-shaped sensors averaging 12y long and
5y wide on both male and female. The wall is thin and
porous with two to four occurring per segment. They
are consistently located distally to the chaetica which
are located at the convergence point of the sensory side
with the scale side of antenna (figure 10, 17).
6) Sensilla styloconica (Figure 18). The sensilla
styloconica are cone-shaped sensory structures mounted
at the apices of stout cuticular pegs. Callahan (1969)
called them taste rods. There is only one per segment,
the size ranging from 16y long on the basal segment to
29y on the distal segment and 7.2y in diameter. They
occur at the distal end of each segment in the center of
the sensory side.
The functions of all the sensors are not known,
however electrophysiological research by Callahan (1968,
1969) and Jefferson et al (1970) indicate the probable
function of some sensors (Table 2).
In both the male and female antennae, the mean total
length is 2.1 times greater than the greatest mean width
of any segments. The female antennae are longer than
the male antennae. This would require that male antennae
*
have more efficient detectors per unit length than the

19
female and consequently might indicate the reason for the
multiple rows of trichodea on the male which are much longer
than the regular ones, and which apparently serve as
pheromone receptors. The great lack of neuroelectrophysio-
logical information makes it impossible to assign reasons
for morphological arrangements of the sensilla and
consequently one can only conjecture about the placement
of certain sensilla on the antennae.
Table 2. Measurements and proposed functions of sensilla
on beet armyworm antenna.
Sensilla types
Proposed
function
k
Length y
Diameter
at base
Sensilla coeloconica
chemoreceptor
temp. § humidity
-
9.6
Sensilla auricillica
unknown
12
4.8
Sensilla styloconica
taste
15.6
7.2
Trichodea types 1, 2
pheromone receiver
chemoreceptor
17-29
1-2
Trichodea type 3
pheromone receiver
38-58
2-5
Trichodea type 4
((Xonly)
pheromone receiver
84-125
4-5
Chaetica cf
55-123
5-10
Chaetica ^
43-91
5-5.5
Bohm bristles ^
24-39
Bohm bristles &
17-23
* n=12

Figure 1. Beet armyworm moth, male

21

Figure 2. Beet armyworm moth, female


Figure 3. Dorso-lateral view of antennal segment
showing convergence of scale surface
with sensory surface. Distal portion
of antenna with dorsal surface to the
right (X898)
Figure 4. Lateral view of the ventral surface of
the basal portion of antenna (X705)

25

Figure 5
Figure 6
Most distal segment of the antenna
showing sensors covering most of
the circumference (X1410)
Chaeticum and trichodea on segment
near base of antenna (X2926)


Figure 7
Bohm bristles on scape dome of male
(X900)
Figure 8. Close-up of Bohm bristles on scape
dome of female (X2667)

29

Figure 9
Close-up of chaeticum on the antenna
(X7182)
Figure 10
Sensilla auricillica and button-like
sensor (X7049)

31

Figure 11. Close-up of chaeticum (X6835)
Figure 12. Short porous trichodea (X10640)

33

Figure 13. Long porous trichodea (X5060)
Figure 14. Long porous trichodea (X13,333)

35

Figure 15. Non-porous trichodea (X6835)
Figure 16. Sensilla coeloconica (X6650)


Figure 17. Sensilla auricillica (X6835)
Figure 18. Sensilla styloconica (X4430)


40
2) Wings
Wings can be differentiated into certain zones based
upon the types of scales found there. These zones do not
correspond with wing venation. Approximate zones for both
sexes and both wings (dorsal and ventral) are shown in
Figures 19 and 20. In general the zones are similar on
both wings dorsally and ventrally and in both sexes except
for the ventral surface of the forewing which will be
discussed later. Zone 1 usually takes up about the anterior
one-fourth of each wing and zone 2 takes up the remainder
of the wing. The third zone was the border consisting of
3 to 5 rows of scales.
Dorsal forewing: Scales found in zone 1 (Figure 21)
of both male and female moths gradually increase in
width from the shaft to the tip. They are serrate at the
tip with 3 to 6 points in the males and 4 to 6 in the
females. Average lengths are 292y and 280y in males and
females, respectively. Average width is the same (41y)
for both sexes. Pigmentation is more heavily concentrated
down the mid-line and the outer margin of the scale and
across the apex. The scales in the female are darker than
in the male.
There are two types of scales in zone 2. One type is
similar to those in zone 1 in that they gradually increase
in width from the base to the apex. The length and width
of this type scale is 262 x 47y for males and 276. x 56y for females
Scales are serrate at the tip with 5 to 6

41
points for males and 5 to 7 for females. Heaviest
pigmentation is concentrated along the mid-line from the
shaft to the distal end of the scale and across the apex.
Interspersed under the serrate scales are the basal
scales. These are blunt tipped scales 120 x 45y (males)
and 134 x 50y (females). The blunt tip may be indented
at 3 or 4 points in the females. There is less pigmenta
tion in these scales than in the serrate scales (Figure 22).
The border scales are confined to 3 to 5 rows on
the outer edge of the wing. These are elongate and the
shaft comprises approximately half of the length. The
width gradually increases from the shaft to the tip and
both shaft and scale are pigmented. Scales are larger in
males 610 x 78y with 5 to 9 points compared to 470 x 53y
with 4 to 5 points in the female border scales. Width of
the shaft is 7.2y for males and only 5.0y for females
(Figure 23).
Ventral forewing: There are three zones in both male
and female. Zone 1 takes up about one fifth of the wing
area and zones 2 and 3 about two fifths each. The only
difference between males and females is that zones 1 and 3
are adjacent at the base of the wing in the males while in
the female, zone 2 completely separates zones 1 and 3
(Figure 20).
Scales found in zone 1 of both male and female moths
gradually increase in width from the shaft to the tip.
They are serrate at the tip with 4 to 6 points in the males
and 3 to 5 points in the females. Average lengths are 312

42
and 251y in males and females, respectively. Average
widths are 56 and 44y respectively (Figure 24).
There are two types of scales in zone 2. One type
is serrate, similar to those in zone 1 with 6 to 7 points
for males and 4 to 6 points for females. The length and
width of this type scale is 280 x 50y for males and 307 x 49y
for females. The second type consists of basal scales
which are interspersed under the serrate scales. These
scales are shorter and blunt at the tip (Figure 25), with
a slight inward taper. Average measurements of these scales
are 169 x 52y and 140 x 51y in males and females, respectively.
Covering scales in zone 3 are similar in both males
and females. They are blunt tipped, but there are sometimes
indentions in females (Figure 26). The ultrastructure is
shown in Figure 28. Measurements are 315 x 55y and
308 x 51y in males and females, respectively. There are
blunt basal scales interspersed under the covering scales
in males. Their measurements are 96 x 48y There is no
evidence of basal scales in females.
There is a sac-like structure (Figure 27) covered
with spine-like scales at the posterior base of zone 3
(where the forewing and hindwing are joined). A sexual
dimorphism was found with the scales smooth and larger
at their base in females (Figure 29) while the scales are
stronger and the diameter is about the same for the entire
length in males (Figure 30). The function of the sac-like

43
structure is not known but it may minimize friction between
the wings and facilitate the movements of both wings.
Dorsal hindwing: There are two zones in both males
and females. Zone 1 covers the anterior one-fifth of the
hindwing and zone 2 takes up the remainder. The anterior
*
and posterior edges of the hindwing have many piliform
(hair-like) scales varying from 600 to 1200y long and
3.5 to 6y wide. Only the males have these piliform scales
interspersed in both zones 1 and 2, (Figure 31), there
are none in the females in either zone. Covering scales
are mostly light gray or white except the scales on the
veins have darker pigmentation.
The covering scales in zone 1 are serrate with 2 to 5
points in males and 4 to 6 points in females. Pigmentation
in zone 1 is darker than in zone 2. The measurements are
228 x 52y for males and 252 x 58y for females. The basal
scales are blunt tipped and interspersed underneath the
covering scales. Average measurements are 138 x 50y .
The covering scales in zone 2 are serrate with 2 to 4
points for males and 4 to 6 points for females (Figure 32).
Their average measurements are 220 x 55y (maTe^) and 238 x 53y
(females). White scales are predominant. There is no pig
mentation in the females compared to a slightly darker pig
mentation in the males. Blunt tipped basal scales are
interspersed beneath the serrate scales. Their average
measurements are 170 x 48y .
The border scales are serrate with 3 to 5 points in the
males and 4 to 5 points in the females. The shaft is one half

44
the total length of the scale. Their length varies from
438 to 860y in males and 425 to':854y in females. The
average width is 40y in males and 64y in females. The
scales are heavily pigmented. The width of the peduncle
varies from 4.5 to 6y. The most distinguishing
characteristic to separate males from females is the
frenulum spine number: there is only one in the males but
there are three and sometimes four in the females.
Ventral hindwing: The zonal division is similar to
thevoneof the dorsal surface. Covering scales in zone 1,
are serrate with 4 to 5 points for both sexes (Figure 33).
Their measurements are 252 x 48y in males and 225 x 51y
in females. The scales are pigmented. The basal scales
are blunt tipped and measure 101 x 4 9y.
All of the scales are white in zone 2. The covering
scales are serrate with 3 to 5 points in males and 3 to 4
points in females. Lengths of the scales are much shorter
in females compared to those of males 125 to 240y but the
width is approximately the same, 50y in males and 53y
in females. The basal scales are blunt tipped and inter
spersed beneath the covering scales. Their measurements
are 100 x 51y in males and 103 x 47y in females (Figure 34).
There are four colors of scales: orange, white, gray
and black with all variations between the last two. The
color is not structural but due to pigment grains inside
the scale. The white scales do not contain any pigment.
There are no apparent differences at low magnification in
form of different colored scales but the upper surface of

Figure 19. Fore- and hind-wing (dorsal) surface
showing zonal division for both male
and females (zone 1 shaded, zone 2
unshaded).

46

Figure 20. Upper: zonal division of forewing
(ventral surface) in males
Middle: zonal division of forewing
(ventral surface) in females
Lower: zonal division of hindwing
(ventral surface) in both males and
females


Figure 21. Dorsal forewing scales in zone 1
(X253)
Figure 22. Dorsal forewing covering and basal
scales in zone 2 (X253)


Figure 23. Border scales on dorsal forewing (X253)
Figure 24. Scales on ventral forewing in zone 1
(X253)

52

Figure 25. Basal scales and covering scales on
ventral forewing in zone 2 (X253)
Figure 26. Scales on ventral forewing in zone 3
(X253)

54

Figure 27. Spine-like scales on posterior base
of ventral forewing on sac-like
structure and regular scales in
zone 3 (X226)
Figure 28. Ultrastructure of scales in zone 3
(X6317)

56

Figure 29. Scales on anterior anal area of the
forewing (female, ventral) (X4522)
Figure 30. Scales on anterior anal area of the
forewing (male, ventral) (X2660)


Figure 31. Dorsal hindwing: scales in zone 1
and piliform scales (X253)
Figure 32. Dorsal hindwing: scales in zone 2
(X253)

60

Figure 33. Ventral hindwing: scales in zone 1
(X253)
Figure 34. Ventral hindwing: scales in zone 2
(X253)


Figure 35. Ultrastructure of orange scale showing
high longitudinal ribs and circular
cross-ribs (X4985)
Figure 36. Ultrastructure of gray scale showing
shallow grooves and irregularly
patterned cross-ribs (X5852)

64

Figure 37. Ultrastructure of scale on ventral
hindwing in zone 2 showing smooth groove
without perforations (X4985)
Figure 38. Ultrastructure of border scale on
ventral hindwing showing smooth groove
with perforations (X5852)

66

Figure 39. Ultrastructure of the scale on dorsal
forewing in zone 2 showing straight
cross-ribs (3(4985)
Figure 40. Ultrastructure of scale on dorsal
hindwing in zone 2 showing curved
cross-ribs (X4985)


69
scent ring (Jefferson et al, 1968). There was only one
exception in the subfamily Amphipyrinae where the species
Spodoptera litura has a glandular epithelium covering
the entire 9th abdominal segment.
The scent glands are situated in the non-sclerotized
I
area, between the 8th and 9th abdominal segments (Figure 41)
contrary to Hammad's study on the beet armyworm (1961).
A close-up picture of the scent gland (Figure 42) shows
clearly glandular cells and the wavy spongy surface of the
scent gland (Figure 43). There were different types of
scales in the tip of the abdomen area but none of them are
glandular scales as described by Hammad. There is no
evidence of special secretory ducts in the epithelial
cells. The pheromone is supposed to exude through the
non-sclerotized area. The diameter of the scent glandular
cells is about 10-15y. The wavy surface of the gland area
(microvilli) indicates that when the tip of the abdomen
is extruded the glandular cells will expand fully through
the largest surface and hence, provides the maximum release
of pheromone. The location and structure of the scent
gland of the beet armyworm is therefore similar to that
of Spodoptera ornithogalli described by Barth (1961).
4) Reproductive System
a) External genitalia
The genital complex of Lepidopteran females includes
the seventh through tenth abdominal segments. The eighth

70:
the orange scales have higher longitudinal ribs and the
cross ribs are consistently circular and accentuated when
viewed at 4400X (Figure 35). The gray or black scales
have relatively smooth, shallow grooves between the ribs
and the cross ribs have no regular pattern (Figure 36).
Preliminary research on the ultrastructure of the
scales at magnifications in excess of 4000X, revealed
differences that offer possibilities for further clas
sification of scale types. There are distinct differences
in the structure of the ribs and cross ribs. The groove
is smooth without perforations (Figure 37) or with
perforations in some scales (Figure 38). The groove in
others is perforated with numerous large openings (Figure
39). The cross ribs can be straight (Figure 39) or curved
(Figure 40). Another variation is found in border scales
on the forewing where every third or fourth rib is
thickened. Much more could be done on the subject of
ultrastructure of wing scales and a comparative study of

various families of moths could reveal some very interesting
and meaningful information on relationships throughout
the order.
3) Scent Glands
Scent glands are situated in the ventral intersegmental
area between the 8th and 9th abdominal segments. They belong
to type 2 with ventral sac (Amphipyrinae) compared to type 1
with a dorsal sac or fold (Plusiinae) and type 3 with a

Figure 41. Scent glands located between VUIth
and IXth abdominal segments. Dark
color: sclerotized area

VIIIth

Figure 42. The scent gland in the intersegmental
area between the 9th sternite (on the
right) and the 8th sternite (on the
left). Tip of abdomen at top of pic
ture
Figure 43. Close-up showing wavy surface of the
scent gland and glandular cells under
neath. 8th abdominal sternite visible
on the left. Tip of abdomen at top
of picture


75
abdominal segment of S. exigua is modified with two lateral
plates which serve as an ovipostor (Figure 44-46). These
plates have three types of sensilla': trichodea, button
like, and sensory hairs (Figure 47). Scales are also
observed on the inside of the plates (Figure 46).
The male genital complex of Lepidoptera includes the
eighth, ninth, and tenth abdominal segment. The external
male genitalia in the dorsal view (Figure 48) consists
of the gnathos and 3 spine-like structures. The median
spine-like structure, common to most Lepidoptera, is
the uncus which articulates basally with the tegumen (a
structure shaped like a hood or inverted trough lying
dorsal of the anus). The paired spines articulate basally
with the vinculum which is a U-shaped sclerite derived
from the 9th abdominal sternite. Its arms articulate
dorsally with the tegumen and its caudal margin with the
harpes (or claspers). These two lateral hooks do not
occur in some other genera of Noctuidae i.e. Feltia
subterrnea or Heliothis zea These 3 spines apparently
help the male position the female and hold her during
copulation (Figure 48). The ventral view (Figure 49),
shows the underside of the tegumen and uncus including
the scale sockets on the tegumen. In Figure 50, the
claspers form a V with the uncus between. The claspers
are thickly clothed with scales which may have a sensory
function (Figure 51).

76
Thus the external genitalia of the male consists of
the vinculum which lies ventral to the aedeagus. The left
and right arms are actually a single piece forming the
sternum of the ninth abdominal segment. The tergal area
of the ninth segment, called the tegumen, is fused with
the coxosternalarc, the vinculum, to form the base
(Figure 49) of the male genitalia. The paired claspers
are appendages of the 9th segment and articulate at the
coxopodite area of the vinculum. The uncus and aedeagus
are structures of the tenth segment. Some of the same
sensilla that are found on the antennae are found on the
male genitalia: such as chaeticum (Figure 52), and
trichodea. The ultrastructure of the scales (Figure 53)
shows similar longitudinal ridges and transverse veins as
found in the wing scales but without the holes.
The striking difference between the male and female
genitalia is that there are many more scales and very few
sensilla around the male genitalia compared to the female.
Why sensors are much more numerous in the female genitalia
is not known, however, it is likely associated with the
necessity of the female to locate a suitable oviposition
site using the ovipositor as a test organ.
b) Reproductive organs
The major morphological difference between repro
ductive systems of noctuid species are found in the bursa
copulatrix and "ovipositor" of the female and in the

claspers or harpes, aedeagus and cuticular portion of
the ductus ejaculatorius simplex of the male.
The female reproductive system consists of a pair
of ovaries which open to a pair of lateral oviducts
i
(Figure 54). Each ovary is composed of 4 ovarioles (or
egg tubes). Ovariole development of the oocytes is pan-
oistic. The maturity of the eggs is indicated by the
color: white at the beginning, then pink-purple, and
finally greenish when the eggs are mature. The two
lateral oviducts join the median oviduct which opens to
the gonopore (oviporus and anus) at the 9th segment.
Two other glands open to the gonopore:
1) The paired accessory glands consist of small
and long tubules which are enlarged at the
base to function as reservoirs of the accessory
glands and open to a median duct joining the
gonopore.
2) The spermatheca also opens to the gonopore. It
is composed ot three parts:
a) large lobe (utriculus) of spermatheca
b) upper loop of ductus receptaculi (spermathecalduct)
c) convoluted area and lower loop of ductus receptacul
There are two ducts at the base of the spermatheca,
one opening to the gonopore and the other leading to the
base of the bursa copulatrix.
4
The gonopore which consists of oviporus and anus is
on the ninth abdominal segment while the copulatory vulva
opens on the eighth abdominal segment.

"3
The bursa copulatrix is the most conspicuous organ
in the female insect. The sides are twisted and ridged
with sclerotized ribs. At the top of the sac-like organ
is the place where the capsules of the spermatophores
are formed. The number of spermatophores indicates the
number of copulation times. The most spermatophores
found in the bursa copulatrix of any moth was four. They
accumulate one after another. Williams (1948) listed
three classes of Lepidoptera using spermatophores as
criteria: class A, having the aperture of the sperma-
tophore in direct contact with the seminal duct, of which
the beet armyworm is an example, class B, having a large
secretion-filled reservoir between the aperture of the
spermatophore and the seminal duct and class C, which
includes a few primitive families that have no seminal
duct and only one external opening instead of two as is
typical of most Lepidoptera. The spermatophore is com
posed of a capsule and a sclerotized tube or collum
(Figure 55). The neck-connection between the capsule and
the collum is elbowed making the capsule vertical to the
tube. The capsule loses its spheric shape and becomes
flattened when the sperm are released through the seminal
duct but the collum remains a hard sclerotized structure
during the life time of the female.
The adult male reproductivesystem has only one
fused testis as compared to two separate testes in the last
larval instar. The two large bean-like testes in the

.79
Table 3. Measurements of female internal reproductive
organs and spermatophore.
Organs Mean length (in mm)
Accessory glands 5.5
Reservoir of accessory glands .8
Spermatheca (utriculus) 1.2
Spermathecal duct 1.6
Lower loop of ductus
receptaculi
.6
Bursa copulatrix
3.0
length, 1.2 width
Ovarioles
29.1
Vaginal duct
1.5
Seminal duct
1.9
Oviductus communis
2.5
Lateral oviduct
1.8
Spermatophore
(Length)
(Width)
Capsule
1.2-2.0
1.0-1.3
i
Neck
1.4-2.0
.2^.3(diameter)
Collum
3.0-4.0
.2-.3(diameter)
*n=6
larval stage shrink and fuse in the
prepupal stage as
the larva shrinks and
decreases in size.
The moth testis
is located around the fourth and fifth abdominal segments.
It is spherical and rose-colored. The paired seminal
vesicles lead from the testis to the vas deferens which

.80
open into the ductus ejaculatorius duplex near the
midpoint (Figure 56). The seminal vesicles are about
three-times as wide as the vas deferens. Both are creamy-
white like the remaining glands and ducts of the organs.
The two accessory glands-as two parallel ducts-are
joined together their entire length before they open into
the basal end of the ductus ejaculatorius duplex. The
latter fuses into the ductus ejaculatorius simplex which
is the longest duct of the reproductive organ. About
one-sixth of the distance from the beginning, there is
an enlargement of the duct. The ductus ejaculatorius
simplex leads to the endophallus. The aedeagus is the
sclerotized part surrounding the endophallus.
Table 4. Measurements of male internal reproductive
organs.
Organs Mean length
Seminal vesicles
1.5
Vas deferens
2.0
Accessory glands
24.0
Ductus ejaculatorius
duplex
6.1
Ductus ejaculatorius
simplex
51.2
Testis
1.2
*
(in mm)
(in diameter)
*n=6

Figure 44. Ovipositor showing sensilla on
extreme tip (X133)
Figure 45. Close-up of ovipositor opening (X253)

STM
82

Figure 46. Close-up of ovipositor (X525)
Figure 47. Sensilla on dorsal posterior
ovipositor (X1330)

84

Figure 48. Dorsal view of male genitalia showing
gnathos, uncus, and spines of claspers
(X665)
Figure 49. Male tegumen supporting uncus with
claspers on either side (X825)

86

Figure 50. Dorsal view showing uncus and
claspers (X66)
Figure 51. Inside surface of claspers of male
genitalia (X452)

88

Figure 52. Sensilla and scales on outside of
the clasper; male genitalia (X1463)
Figure 53. Ultrastructure of scale inside of
clasper; male genitalia (X7182)

90
(

Figure 54. The female reproductive system:
A.
B.
C.
D.
E.
F.
G.
H.
I.
J.
K.
L.
bursa copulatrix
vaginal duct
vulva
ovaries
lateral oviduct
median oviduct
oviporus and anus (gonopore)
spermatheca (utriculus)
spermathecal duct
lower loop of ductus receptacul
accessory gland
reservoir of accessory gland

92

Figure 55. The spermatophore:
A. capsule
B. neck
C. collum
D. sperm bundles

94
L
3 mm
j

Figure 56. The male reproductive system:
4
A. testis
B. seminal vesicle
C. vas deferens
D. accessory gland
E. ductus ejaculatorius duplex
F. ductus ejaculatorius simplex
G. aedeagus

iziizig
i i ii 1 1
- 96

97
B. Egg
Eggs are oblong spheroid in shape and circular in
cross section, with a diameter of approximately o.42 mm.
They are greenish when oviposited, turn cream-colored
within a few hours and finally become dark just before
hatching due to the black color of the larval head. They
are laid in clusters of 5 to over 100 in a single layer
and are covered with whitish scales from the tip of the
female abdomen for the early masses of eggs. Masses of
eggs oviposited later are often not covered because the
female moth has lost almost all the setae at the abdominal
tip (Figure 57). The micropyle, located at the top, is
surrounded by a petal-like pattern with the number of
petals varying from 7 to 11 (Figure 58). The whole egg
is composed of many concave surfaces delineated by higher
r
ridges (Figure 58). Many tiny pores, called aeropyles,
can be seen distributed at the edges of the ridges at
1430X (Figure 59). These aeropyles play a principal
role in gas and moisture exchange (Hinton, 1969).
C. Larva
There are five larval instars and on occasion six.
The first instar larva is about 1 mm long with a whitish
body and black head. The body color is highly variable
from specimen to specimen in later instars, ranging from
light green to olivaceous to near black. The head becomes
lighter in color being brownish with a number of near-

Figure 57. Beet armyworm eggs partly covered
with scales from tip of female
abdomen (X133)
Figure 58. Apex of egg showing micropyle and
chorion design (X931)

99

Figure 59. Egg surface showing aeropyles (pores)
on edge of ridges (X1430)
Figure 60. Ocelli and antenna of first instar
larva, dorso lateral view (X665)


white reticulations on the epicranium. The width of
the first instar head capsule is .25 mm (n=60). Full
grown larvae measure from 30 to 35 mm.
Only the first instar larva was examined with the
scanning electron microscope and its description follows:
The 6 ocelli are arranged in a semi-circular position
and are unequal in size: the third ocellus is the largest
while the first and the sixth ocelli are smaller than the
others (Figure 60). Setae on the head are more pointed
than those on the body, with lengths varying from 0.02
to 0.08 mm. They are usually curved or bent near the tip
while the body setae are more or less straight and thicker.
The body setae are also inserted in a raised pinaculum
which has a much larger diameter and is navel-like (Figure
61), whereas those on the head have only a simple
peritreme (Figure 63). There are numerous tiny spicules
on the body evenly distributed almost everywhere except
on some transverse folds and the intersegmental positions
of the larva (Figure 62).
D. Chromosome Number
Chromosomes are more or less spherical (dot-like),
similar to those found in other Noctuids. Definitive
chromosome counts with photographic confirmation were
obtained from five male larvae and four adults. The
haploid chromosome number of the beet armyworm is n=31
(Figure 64, 65). A haploid set of 31 chromosomes is the

Figure 61. Microspines and setae on first instar
larva (X1596)
Figure 62. Spiracle of first instar larva (X1410)

104

Figure 63. Overall view of anterior portion of
first instar larva (X300)

106

107
most common number found to date in the Noctuidae
(Robinson, 1971). The haploid number of chromosomes
varies from 29 to 34 among the 36 Noctuid species
studied so far (Robinson, 1971). Another member of
the same genus, Spodoptera litura (=Prodenia litura)
has the same number (31) of chromosomes as S. exigua
(Gupta, 1964).
Sperms and spermatids were observed in the prepara
tion taken from the adults testes (Figure 66, 67). The
/
head of the sperm containing the nucleus looks like the
tail but thicker. It has an oblong form followed by a
long filamentous tail (Figure 67). The length of
the sperms varies from 12.6 to 23.5p.

Figure 64. Chromosomes of the beet armyworm
observed under microscope with phase
(n=31) (X1197)
Figure 65. Chromosomes of the beet armyworm
observed under microscope without
phase (X1197)

109

Figure 66. Bundles of sperms in testis (X 1197)
Figure 67. Two sperms among nucleus division
in testis (X1197)

Ill

CHAPTER V
CONCLUSIONS
Based on this research the following morphological
distinctions have been determined for the beet armyworm:
1. The female antennae are longer than male
antennae.
2. There are six morphologically distinct types of
sensilla on the antennae of each sex. The male,
however, does have a distinct pattern arrange
ment of the long sensilla trichodea.
3. Wing areas can be divided into distinct zones
based on types of scales.
4. Sexes can be distinguished by the number of
frenulum spines on the hindwing. The male has
one while the female has three and sometimes four.
5. Scent glands are present in the ventral inter-
segmental area between the eighth and ninth
abdominal segments.
6. The female has two .lateral plates on the eighth
abdominal segment which serve as the ovipositor.
Three types of sensilla are found on these plates.
7. The ninth abdominal segment of the male has a
curved uncus and two lateral hooks. These
hooks do not occur in all other noctuid genera.
8. Externally, there are many more scales and very
few sensilla on the male genitalia compared to
the female.
9. The female ovary is composed of four ovarioles.
The distinct bursa copulatrix is described as
well as the spermatophore.
10.The haploid chromosome number for this species
was determined to be n=31.
112

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BIOGRAPHICAL SKETCH
Ngo Dong was born October 4, 1937, in Hanoi North
VietNam. In 1961, he received the B.S. from the
University of Hue, South VietNam, and became a teaching
assistant in Zoology of the University of Hue. In 1967,
he was promoted to Chief of the Zoology Laboratory. In
1968, he became Assistant Dean for Student Affairs in
the Faculty of Science. In March 1971, he was sent by
the University of Hue to take higher degrees at the
University of Florida.
From 1971 until the present time he has pursued work
toward the degree of Doctor of Philosophy in Entomology.
On January 11, 1963, Ngo Dong was married to Ton Nu
Thanh Chau and his family now includes four children,
three boys and one girl.
He is a member of the Newell Entomological Society,
the Florida Entomological Society and the Entomological
Society of America.
118;:

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Professor of Entomology
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as a dissertation for the degree of Doctor of Philosophy.
u
i
0
Harvey ^
Professor
Cromroy
of Entomology
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presentation and is fully adequate, in scope and quality,
as a dissertation for the degree of Doctor of Philosophy.
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Professor of Entomology
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presentation and is fully adequate, in scope and quality,
as a dissertation for the degree of Doctor of Philosophy.
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Professor of Entomology

I certify that I have read this study and that in
my opinion it conforms to acceptable standards of scholarly
presentation and is fully adequate, in scope and quality,
as a dissertation for the degree of Doctor of Philosophy.
ames Soule
Professor of Fruit Crops
This dissertation was submitted to the Graduate Faculty
of the College of Agriculture and to the Graduate. Council,
and was accepted as partial fulfillment of the require
ments for the degree of Doctor of Philosophy.
June, 1974
Dean, Graduate School



Figure 46. Close-up of ovipositor (X525)
Figure 47. Sensilla on dorsal posterior
ovipositor (X1330)


.80
open into the ductus ejaculatorius duplex near the
midpoint (Figure 56). The seminal vesicles are about
three-times as wide as the vas deferens. Both are creamy-
white like the remaining glands and ducts of the organs.
The two accessory glands-as two parallel ducts-are
joined together their entire length before they open into
the basal end of the ductus ejaculatorius duplex. The
latter fuses into the ductus ejaculatorius simplex which
is the longest duct of the reproductive organ. About
one-sixth of the distance from the beginning, there is
an enlargement of the duct. The ductus ejaculatorius
simplex leads to the endophallus. The aedeagus is the
sclerotized part surrounding the endophallus.
Table 4. Measurements of male internal reproductive
organs.
Organs Mean length
Seminal vesicles
1.5
Vas deferens
2.0
Accessory glands
24.0
Ductus ejaculatorius
duplex
6.1
Ductus ejaculatorius
simplex
51.2
Testis
1.2
*
(in mm)
(in diameter)
*n=6


Figure 39. Ultrastructure of the scale on dorsal
forewing in zone 2 showing straight
cross-ribs (3(4985)
Figure 40. Ultrastructure of scale on dorsal
hindwing in zone 2 showing curved
cross-ribs (X4985)


84


60




2
is to describe the internal and external morphology of
this insect with the aid of the scanning electron micro
scope with special emphasis on details of the reproduc
tive and external sense organs.


17
d) Type 4: These are extremely long trichodea found only
on the male beet armyworm moth where they are arranged in
six rows per segment with 5-6 trichodea per row measuring
84-125p. Three rows originate ventro-laterally on each
side of the antenna at the convergence point between the
scale side and the sensory side. The long trichodea
orient diagonally in rows.
All of the other sensilla types are located between
the rows of long trichodea. Antennal segments bearing the
long trichodea rows extend from the base of the antenna
to approximately the 40th segment. Sensilla on the re
maining segments are comparable to those on the female
antenna. Ultrastructure of the nonporous trichodea (type 3)
shows a fluted condition arranged circularly (Figure 15)
4) Sensilla coeloconica (Figure 16). These sensilla
have been referred to as pit peg or picket-fence sensors
(Callahan, 1969). Each sensillum consists of a porous peg
with inward slanting spines oriented circularly around its
periphery. Twelve to fifteen spines are arranged in a
circular fashion with a fluted peg in the center. Spines
curve inward toward the tip of the peg. Diameter of the
pit is about 9-10y on both male and female antenna. Pits
occur randomly over the sensory surface of antenna with
six to ten per segment. Significantly more sensilla were
found in the 1st, 2nd, and 25th segments of females and
on the 55th and penultimate segments of males (Jefferson
et al. 1970).


VIIIth


Figure 17. Sensilla auricillica (X6835)
Figure 18. Sensilla styloconica (X4430)




18
5) Sensilla auricillica. This type of sensillum has
been called spoon sensor (Griffith, 1968) and shoe-horn
sensor (Callahan, 1969), however, sensilla auricillica
as used by Jefferson et al. (1970) is more consistent
with other latin terms. Sensilla auricillica are ear
like or spatula-shaped sensors averaging 12y long and
5y wide on both male and female. The wall is thin and
porous with two to four occurring per segment. They
are consistently located distally to the chaetica which
are located at the convergence point of the sensory side
with the scale side of antenna (figure 10, 17).
6) Sensilla styloconica (Figure 18). The sensilla
styloconica are cone-shaped sensory structures mounted
at the apices of stout cuticular pegs. Callahan (1969)
called them taste rods. There is only one per segment,
the size ranging from 16y long on the basal segment to
29y on the distal segment and 7.2y in diameter. They
occur at the distal end of each segment in the center of
the sensory side.
The functions of all the sensors are not known,
however electrophysiological research by Callahan (1968,
1969) and Jefferson et al (1970) indicate the probable
function of some sensors (Table 2).
In both the male and female antennae, the mean total
length is 2.1 times greater than the greatest mean width
of any segments. The female antennae are longer than
the male antennae. This would require that male antennae
*
have more efficient detectors per unit length than the


STM
82


9
Histological studies of 4-day-old virgin moths were
made of 3 parts; head-thorax, abdomen and wings. These
parts were put into boiling Bouin's fluid, allowed to
cool to room temperature for 2 days and then washed in
701 alcohol. Specimens were then imbedded in paraffin.
Longitudinal and transverse sections were cut at 6 microns.
Sections were stained with Mallorys triple stain method.
Histological slides were observed with the Zeiss Photo
microscope II using Nomarski differential interference
contrast. Photomicrographs were made of selected sections.
All measurements of wing scales were made with the
aid of a micrometer disc in a compound microscope. All
dimensions represent an average of measurements made on
12 scales. The measurements of internal reproductive
organs were determined by measuring the structure on
photographs with a millimeter rule photographed at the
same microscope setting.
C. Chromosome Number
Chromosomes were studied in dividing cells in
the testes of larvae of male moths. The testes were taken
from the last larval stage and from the male adults 2 to 3 days
after emergence. The te.stes were removed with No. 5 watch
maker forceps and placed on a standard microscope slide.
The testes were then macerated and a few drops of lacto-
aceto-oreein stain (Emmel, 1969) added. This preparation


107
most common number found to date in the Noctuidae
(Robinson, 1971). The haploid number of chromosomes
varies from 29 to 34 among the 36 Noctuid species
studied so far (Robinson, 1971). Another member of
the same genus, Spodoptera litura (=Prodenia litura)
has the same number (31) of chromosomes as S. exigua
(Gupta, 1964).
Sperms and spermatids were observed in the prepara
tion taken from the adults testes (Figure 66, 67). The
/
head of the sperm containing the nucleus looks like the
tail but thicker. It has an oblong form followed by a
long filamentous tail (Figure 67). The length of
the sperms varies from 12.6 to 23.5p.


44
the total length of the scale. Their length varies from
438 to 860y in males and 425 to':854y in females. The
average width is 40y in males and 64y in females. The
scales are heavily pigmented. The width of the peduncle
varies from 4.5 to 6y. The most distinguishing
characteristic to separate males from females is the
frenulum spine number: there is only one in the males but
there are three and sometimes four in the females.
Ventral hindwing: The zonal division is similar to
thevoneof the dorsal surface. Covering scales in zone 1,
are serrate with 4 to 5 points for both sexes (Figure 33).
Their measurements are 252 x 48y in males and 225 x 51y
in females. The scales are pigmented. The basal scales
are blunt tipped and measure 101 x 4 9y.
All of the scales are white in zone 2. The covering
scales are serrate with 3 to 5 points in males and 3 to 4
points in females. Lengths of the scales are much shorter
in females compared to those of males 125 to 240y but the
width is approximately the same, 50y in males and 53y
in females. The basal scales are blunt tipped and inter
spersed beneath the covering scales. Their measurements
are 100 x 51y in males and 103 x 47y in females (Figure 34).
There are four colors of scales: orange, white, gray
and black with all variations between the last two. The
color is not structural but due to pigment grains inside
the scale. The white scales do not contain any pigment.
There are no apparent differences at low magnification in
form of different colored scales but the upper surface of


Abstract of Dissertation Presented to the
Graduate Council of the University of Florida
in Partial Fulfillment of the Requirements for the
Degree of Doctor of Philosophy
MORPHOLOGICAL STUDIES ON THE BEET ARMYWORM
SPODOPTERA EXIGUA (HUBNER) (LEPIDOPTERA: NOCTUIDAE)
By
Ngo Dong
June, 1974
Chairman: Dale H. Habeck
Major Department: Entomology and Nematology
The beet armyworm Spodoptera exigua (Hubner)
(Lepidoptera: Noctuidae), a nearly cosmopolitan species,
is an economically important pest in Florida and other areas.
Morphological studies were concentrated on the antenna, wing
scales, and the external genitalia and reproductive system
of the adult, the egg, and first instar larva.
Female antennae are longer than male antennae. Six
morphologically distinct types of sensilla were found on
the antennae of each sex: Bohm bristles, chaetica,
trichodea, auricillica, styloconica and coeloconica.
However, only the male has the long sensilla trichodea.
These are arranged in a distinct pattern. Wings can be
divided into distinct zones based on types of scales:
XI1


Figure 29. Scales on anterior anal area of the
forewing (female, ventral) (X4522)
Figure 30. Scales on anterior anal area of the
forewing (male, ventral) (X2660)


Figure 33. Ventral hindwing: scales in zone 1
(X253)
Figure 34. Ventral hindwing: scales in zone 2
(X253)


92


Figure 2. Beet armyworm moth, female




69
scent ring (Jefferson et al, 1968). There was only one
exception in the subfamily Amphipyrinae where the species
Spodoptera litura has a glandular epithelium covering
the entire 9th abdominal segment.
The scent glands are situated in the non-sclerotized
I
area, between the 8th and 9th abdominal segments (Figure 41)
contrary to Hammad's study on the beet armyworm (1961).
A close-up picture of the scent gland (Figure 42) shows
clearly glandular cells and the wavy spongy surface of the
scent gland (Figure 43). There were different types of
scales in the tip of the abdomen area but none of them are
glandular scales as described by Hammad. There is no
evidence of special secretory ducts in the epithelial
cells. The pheromone is supposed to exude through the
non-sclerotized area. The diameter of the scent glandular
cells is about 10-15y. The wavy surface of the gland area
(microvilli) indicates that when the tip of the abdomen
is extruded the glandular cells will expand fully through
the largest surface and hence, provides the maximum release
of pheromone. The location and structure of the scent
gland of the beet armyworm is therefore similar to that
of Spodoptera ornithogalli described by Barth (1961).
4) Reproductive System
a) External genitalia
The genital complex of Lepidopteran females includes
the seventh through tenth abdominal segments. The eighth


29


Figure 27. Spine-like scales on posterior base
of ventral forewing on sac-like
structure and regular scales in
zone 3 (X226)
Figure 28. Ultrastructure of scales in zone 3
(X6317)


21


5
The morphology and anatomy of the mature larva of
S. littoralis [as Prodenia litura] was described by
Hassan et al. (1958). Murad (1969) described the
musculature of the sucking pump of S. mauritia (Boisduval).
The male and female genitalia of S. mauritia acronyctoides
(Guenee), S. pecten (Guenee), and S. abyssinia (Boisduval)
were described by Chatterjee (1969).
Callahan's work on morphology and histology of
Heliothis zea (1958), was particularly useful and many
of his techniques were followed in this study. The
morphology of the reproductive systems and mating in two
other noctuids Pseudaletia unipuncta (Haworth), and
Peridroma margaritosa (Hubner) were compared to Heliothis
zea (Callahan and Chapin, 1960). Other detailed morpho
logical descriptions of the reproductive systems of other
Lepidoptera include those of Feltia subterrnea (F.)
(Snow and Callahan, 1968), Ephestia kuhniella (Zeller)
(Norris, 1932), Pectinophora gossypiella (Saund.) (Wellso
and Adkisson, 1962), and Dioryctria abietella (D. 8 S.)
(Fatzinger, 1970). Good histological descriptions have
been given for those of H. zea (Callahan and Cascio, 1963)
and E. kuhniella (Musgrave, 1937), and Choristoneura
fumiferana (Clemens) (Outram, 1971).
Bullock and Horridge (1965) reviewed the types of
sensilla occurring on insects. Research by Callahan (1969)
and his associates (Callahan et al. 1968) described
sensilla on the antenna of the corn earworm H. zea moth


88


claspers or harpes, aedeagus and cuticular portion of
the ductus ejaculatorius simplex of the male.
The female reproductive system consists of a pair
of ovaries which open to a pair of lateral oviducts
i
(Figure 54). Each ovary is composed of 4 ovarioles (or
egg tubes). Ovariole development of the oocytes is pan-
oistic. The maturity of the eggs is indicated by the
color: white at the beginning, then pink-purple, and
finally greenish when the eggs are mature. The two
lateral oviducts join the median oviduct which opens to
the gonopore (oviporus and anus) at the 9th segment.
Two other glands open to the gonopore:
1) The paired accessory glands consist of small
and long tubules which are enlarged at the
base to function as reservoirs of the accessory
glands and open to a median duct joining the
gonopore.
2) The spermatheca also opens to the gonopore. It
is composed ot three parts:
a) large lobe (utriculus) of spermatheca
b) upper loop of ductus receptaculi (spermathecalduct)
c) convoluted area and lower loop of ductus receptacul
There are two ducts at the base of the spermatheca,
one opening to the gonopore and the other leading to the
base of the bursa copulatrix.
4
The gonopore which consists of oviporus and anus is
on the ninth abdominal segment while the copulatory vulva
opens on the eighth abdominal segment.


LIST OF FIGURES (Continued)
Figure 64. Chromosomes of the beet armyworm
observed under microscope with
phase (n=31) (X1197) 109
Figure 65. Chromosomes of the beet armyworm
observed under microscope without
phase (X1197) 109
Figure 66. Bundles of sperms in testis (X1197) HI
Figure 67. Two sperms among nucleus division
in testis (X1197) Ill
xx


LIST OF FIGURES (Continued)
Figure 45. Close-up of ovipositor opening
(X253) 82
Figure 46. Close-up of ovipositor (X253) 84
Figure 47. Sensilla on dorsal posterior
ovipositor (X1330) 84
Figure 48. Dorsal view of male genitalia
(X665) 86
Figure 49. Male tegumen supporting uncus with
claspers on either side (X825) 86
Figure 50. Dorsal view showing uncus and
claspers (X66) 88
Figure 51. Inside surface of claspers of
male genitalia (X452) 88
Figure 52. Sensilla and scales on outside
of the clasper; male genitalia (X1465) .90
Figure 53. Ultrastructure of scale inside of
clasper; male genitalia (X7182) 90
Figure 54. The female reproductive system 92
Figure 55. The Spermatophore 94
Figure 56. The male reproductive system 96
Figure 57. Beet armyworm eggs partly covered
with scales from tip of female
abdomen (X133) 99
Figure 58. Apex of egg showing micropyle and
chorion design (X931) 99
Figure 59. Egg surface showing aeropyles (pores)
on edge of ridges (X1430) 101
Figure 60. Ocelli and antenna of first instar
larva, dorso lateral view (X665) .... 101
Figure 61. Microspines and setae on first
instar larva (XI596) 10.4
Figure 62. Spiracle of first instar larva
(1410) 104
Figure 63. Overall view of anterior portion of
first instar larva (X300) 106
x


64


31


Figure 55. The spermatophore:
A. capsule
B. neck
C. collum
D. sperm bundles


CHAPTER III
METHODS AND MATERIALS
A. Rearing
The male and female moths of the beet armyworm used
in this study were obtained from larvae reared on an
artificial medium slightly modified (Bacheler and Emmel,
1974) from that used by Shorey and Hale (1965). All
developmental stages were held at approximately 27 C
and about 871 relative humidity with a 16 hour light
and 8 hour dark day length. Larvae were reared in
half-pint ice cream containers supplied with enough
artificial food to complete larval development. Pupae
were sexed and put into separate 1-pint ice cream
containers except for those used to maintain the colony.
An 8% sucrose solution was continuously available to the
adults.
B. Gross Morphological Studies
For the reproductive system studies, two to three
day-old male and female moths were dissected in phy
siological saline. The reproductive system was separated
from the digestive tract, examined and photographed.
Organs were preserved in alcohol for futher reference.
8


Figure 20. Upper: zonal division of forewing
(ventral surface) in males
Middle: zonal division of forewing
(ventral surface) in females
Lower: zonal division of hindwing
(ventral surface) in both males and
females


41
points for males and 5 to 7 for females. Heaviest
pigmentation is concentrated along the mid-line from the
shaft to the distal end of the scale and across the apex.
Interspersed under the serrate scales are the basal
scales. These are blunt tipped scales 120 x 45y (males)
and 134 x 50y (females). The blunt tip may be indented
at 3 or 4 points in the females. There is less pigmenta
tion in these scales than in the serrate scales (Figure 22).
The border scales are confined to 3 to 5 rows on
the outer edge of the wing. These are elongate and the
shaft comprises approximately half of the length. The
width gradually increases from the shaft to the tip and
both shaft and scale are pigmented. Scales are larger in
males 610 x 78y with 5 to 9 points compared to 470 x 53y
with 4 to 5 points in the female border scales. Width of
the shaft is 7.2y for males and only 5.0y for females
(Figure 23).
Ventral forewing: There are three zones in both male
and female. Zone 1 takes up about one fifth of the wing
area and zones 2 and 3 about two fifths each. The only
difference between males and females is that zones 1 and 3
are adjacent at the base of the wing in the males while in
the female, zone 2 completely separates zones 1 and 3
(Figure 20).
Scales found in zone 1 of both male and female moths
gradually increase in width from the shaft to the tip.
They are serrate at the tip with 4 to 6 points in the males
and 3 to 5 points in the females. Average lengths are 312




CHAPTER II
LITERATURE REVIEW
Few detailed studies on the morphology and histology
of the beet armyworm have been done. The morphology of
the female sex pheromone glands of the beet armyworm was
described along with 7 other noctuid species: Autographa
californica (Speyer), Pseudoplusia includns (Walker),
Rachiplusia ou (Guenee), Feltia subterrnea (Fabricius) ,
Heliothis zea (Boddie), Heliothis phloxiphaga (Grote),
and Heliothis virescens (Fabricius), (Jefferson et al.
1966, 1968). The location of the glands of each species
was described and some comparisons were presented. Hammad
(1961) described scent glands of different noctuid species
Agrotis ypsilon (Hufnagel), Syngrapha circumflexa
(Linnaeus), Earias insulana (Boisduval), Leucania
loreyi (Duponchel), Pyrausta (Ostrinia) nubilalis (Hubner)
Chilo simplex (Butler), Platyedra. gossypiella (Saunders),
and S. exigua. He reported S. exigua scent glands belong
ing to the brush-like type in the 8th abdominal segment.
The external morphology of the antennae of 4 noctuid
species: Trichoplusia ni (Hubner), Heliothis zea, S.
ornithogalli (Guenee), and S. exigua was described and
different types of sensilla were classified but the
3


CHAPTER IV
RESULTS AND DISCUSSION
This research which is basically a descriptive research
study is difficult to present in the standard dissertation
format. For this reason, this section is subdivided into
four sections: adult, egg, larva, and chromosome number.
A. Moth
The beet armyworm moth is about 2.2 cm across the wings
(Figure 1, 2). The forewings are mottled grayish and the
hindwings are off-white with dark scales along the veins and
the border. Males (Figure 1) can usually be distinguished
from females (Figure 2) by the more pointed abdomen tip.
1) Antennae
The antennae of the beet armyworm are setiform with
a large number of flagellar segments referred to subsequently
as the flagellum whereas the first two segments of the
antennae are the scape and pedicel. There is considerable
variation in number of segments from specimen to specimen,
and even between antennae of a particular specimen. The
mean number was 65 segments compared to 63 reported by
12


16
The chaetica on the scale or dorsal surface of the
antenna are more consistent in length and make a smaller
angle in relation to the antennal segment than any of the
other chaetica. These chaetica range from 48y long at
the base of the antenna to 67y at the tip. The angle is
/
15 to 35 in relation to an antennal segment. The
chaetica originate at the distal end of the first row of
scales.
3) Sensilla trichodea. The most numerous sensory hairs
on the antennae can be separated into four types. !a) Type 1
Consists of short porous trichodea having pores arranged in
rows. The latter originate dorsally on the sensillum and
continue a distally downward orientation to the ventral
part of the sensillum (Figure 12). They measure 15-20y
in length and l-2y in diameter at base. Callahan (1969)
called them stubby basiconica. b) Type 2: These are long
porous trichodea measuring 20-30y in length and l-2y in
diameter at the base. The pore rows originate on the
ventral part of the sensillum and extend on both sides of
the sensillum in a dorso-distal direction until the two
rows converge at the mid-dorsal point (Figure 13, 14). Both
types of porous trichodea are thin-walled and are randomly
arranged on the sensory side of the antenna. c) Type 3:
These are nonporous trichodea (Figure 15). They are thick-
walled and measure 38-58y long and 2-5y in diameter at the
base. These sensilla are sharply pointed and arranged
randomly over the entire sensory surface of both male and
female antennae.


46


76
Thus the external genitalia of the male consists of
the vinculum which lies ventral to the aedeagus. The left
and right arms are actually a single piece forming the
sternum of the ninth abdominal segment. The tergal area
of the ninth segment, called the tegumen, is fused with
the coxosternalarc, the vinculum, to form the base
(Figure 49) of the male genitalia. The paired claspers
are appendages of the 9th segment and articulate at the
coxopodite area of the vinculum. The uncus and aedeagus
are structures of the tenth segment. Some of the same
sensilla that are found on the antennae are found on the
male genitalia: such as chaeticum (Figure 52), and
trichodea. The ultrastructure of the scales (Figure 53)
shows similar longitudinal ridges and transverse veins as
found in the wing scales but without the holes.
The striking difference between the male and female
genitalia is that there are many more scales and very few
sensilla around the male genitalia compared to the female.
Why sensors are much more numerous in the female genitalia
is not known, however, it is likely associated with the
necessity of the female to locate a suitable oviposition
site using the ovipositor as a test organ.
b) Reproductive organs
The major morphological difference between repro
ductive systems of noctuid species are found in the bursa
copulatrix and "ovipositor" of the female and in the


Figure 37. Ultrastructure of scale on ventral
hindwing in zone 2 showing smooth groove
without perforations (X4985)
Figure 38. Ultrastructure of border scale on
ventral hindwing showing smooth groove
with perforations (X5852)


7
in color and position. This was the first time the
scales were studied with the scanning electron micro
scope .
Research on the chromosome numbers of Lepidoptera
has been done principally on butterflies, with very
little work on moths in general and on the Noctuidae
in particular. Among the 2,700 species of Noctuidae,
the chromosome numbers of only 36 species have been
reported (Robinson, 1971). The only member of the
genus Spodoptera whose karyotype was determined (Gupta,
1964) was S. litura (as Prodenia litura).


Figure 35. Ultrastructure of orange scale showing
high longitudinal ribs and circular
cross-ribs (X4985)
Figure 36. Ultrastructure of gray scale showing
shallow grooves and irregularly
patterned cross-ribs (X5852)


115
Harvey, L. F. 1876. Canadian Entomol. 8: 54.
Hassan, A. Si, A. M. El Tabey, Sherata, and S. M. Hammad.
1958. The morphology and anatomy of the mature
larvae of Prodenia litura F. (Lepidoptera: Agrotidae
Xenobiinae) Bull, Soc. Entomol. Egypte 42: 291-309.
Hinton, H. E. 1969. Respiratory systems of insect
egg shells. Annu. Rev. Entomol. 14: 343-68.
Jefferson, R. N. and R. E. Rubin. 1970. Sex pheromones
of noctuid moths. XVII. A clarification of the
description of the female sex pheromone gland of
Prodenia litura. Ann. Entomol. Soc. Amer. 63(2):
431-3.
Jefferson, R. N., H. H. Shorey, and L. K. Gaston. 1966.
Sex pheromones of noctuid moths. X. The morphology
and histology of the female sex pheromone gland of
Trichoplusia ni (Lepidoptera: Noctuidae). Ann.
Entomol. Soc. Amer. 59: 1166-9.
Jefferson, R. N., H. H. Shorey, and R. E. Rubin. 1968.
Sex pheromones of noctuid moths. XVI. The morphology
of the female sex pheromone glands of eight species.
Ann. Entomol. Soc. Amer. 61(4): 861-65.
Jefferson, R. N., R. E. Rubin, S. U. McFarland, and H. H.
Shorey. 1970. Sex pheromones of noctuid moths.
XXII. The external morphology of the antennae of
Trichoplusia ni, Hellothis zea, Prodenia ornithogalli,
and Spodoptera exigua. Ann. Entomol. Soc. Amer.
63(5): 1227-38.
Kellogg, V. 1894. The taxonomic value of the scales of
the Lepidoptera. Kansas Univ. Quart., 3: 45-89.
Kinder, E. and Suffert. 1943. Ueber den Feinbau Schillernder
Schmetterlingschuppen von Morpho-typ. Biol. Zentr.
63: 268.
Kolyer, J. M. and Annemarie Reimschuessel. 1970. Scanning
electron microscopy on wing scales of Colias
eurytheme. J. Res. Lepid. 8(1): 1-15.
Kuznetsov, N. Ya.-1915. Fauna of Russia and adjacent
countries. Trans. Mercado. Ed. B. Golek. U. S. Dept.
Com., 148-62.
Mathur, L. M. L. 1968. Morphology of the excretory system
of the noctuid larvae Prodenia litura Fabr. and
Trichoplusia ni Hbn. Indian J. Entomol. 28(1): 61-66.
1969. Morphology of the nervous system of the noctuid
larvae Prodenia litura Fabr. and Trichoplusia ni Hbn.
Indian J. Entomol. 29 (1): 25-33. ~


90
(


Figure 64. Chromosomes of the beet armyworm
observed under microscope with phase
(n=31) (X1197)
Figure 65. Chromosomes of the beet armyworm
observed under microscope without
phase (X1197)


4

variations among the species were slight (Jefferson et
al. 1970).
These are the only known studies on the beet army-
worm, but there are reports on other species of Spodoptera.
Most of these are listed under the generic name Prodenia
which contained the majority of the species before being
synonymized with Spodoptera.
Barth (1961) described the scent glands of S.
ornithogalli and Hammad and Jarczyk (1958) reported on the
morphology and histology of scent glands in S. littoralis
[as P. litura] a closely related species occurring in
Africa and the Middle East.
Many morphological studies have been done on S.
litura (Fabricius), an economically important species
occurring in India, Southeast Asia and some of the Pacific
Islands. Various parts of the nervous system of the
adult moths have been described by Srivastava (1967,
4
1970) and Mathur (1969). The larval nervous system has
been described by Bahadur and Srivastava (1968a, 1968b)
and Srivastava (1972). Srivastava and Mathur also
described the morphology of the cephalic and prothoracic
glands of the mature larva (1963) and the musculature of
the head capsule of the mature larva (1964). Jefferson
and Rubin (1970) clarified the description of the female
sex pheromone gland and Mathur (1968) described the
morphology of the excretory system of the larva. Abnormal
variations in the wing venation were described by
Bhattacherjee and Raghavan (1968).


Figure 23. Border scales on dorsal forewing (X253)
Figure 24. Scales on ventral forewing in zone 1
(X253)


CHAPTER I
INTRODUCTION
The beet armyworm Spodoptera exigua (Hubner) is
nearly cosmopolitan in distribution. Since first re
ported in Oregon (Harvey, 1876) it has gradually spread
throughout the country reaching Florida in 1924 (Wilson,
1934). The larvae are very polyphagous and are important
economic pests on many commercial crops grown in Florida
including tomatoes, chrysanthemums, gladiolus, sweet
corn, ferns, peppers and peanuts.
Difficulties in controlling the beet armyworm with
insecticides along with concern for the environment have
led entomologists to seek alternate methods of control
for this and many other pest insects. These new methods
of control require much more information on basic biology
and morphology of insects. For example, the work on
gametogenesis in the sugarcane borer Diatraea saccharalis
(F.) by Virkki (1963) made possible the radiation and
sterilization procedures for the male moths. The biology
of the beet armyworm has been studied by Wilson (1932, 1934).
However, no detailed morphological studies of the
insect have been done. The objective of this dissertation


Figure 57. Beet armyworm eggs partly covered
with scales from tip of female
abdomen (X133)
Figure 58. Apex of egg showing micropyle and
chorion design (X931)


"3
The bursa copulatrix is the most conspicuous organ
in the female insect. The sides are twisted and ridged
with sclerotized ribs. At the top of the sac-like organ
is the place where the capsules of the spermatophores
are formed. The number of spermatophores indicates the
number of copulation times. The most spermatophores
found in the bursa copulatrix of any moth was four. They
accumulate one after another. Williams (1948) listed
three classes of Lepidoptera using spermatophores as
criteria: class A, having the aperture of the sperma-
tophore in direct contact with the seminal duct, of which
the beet armyworm is an example, class B, having a large
secretion-filled reservoir between the aperture of the
spermatophore and the seminal duct and class C, which
includes a few primitive families that have no seminal
duct and only one external opening instead of two as is
typical of most Lepidoptera. The spermatophore is com
posed of a capsule and a sclerotized tube or collum
(Figure 55). The neck-connection between the capsule and
the collum is elbowed making the capsule vertical to the
tube. The capsule loses its spheric shape and becomes
flattened when the sperm are released through the seminal
duct but the collum remains a hard sclerotized structure
during the life time of the female.
The adult male reproductivesystem has only one
fused testis as compared to two separate testes in the last
larval instar. The two large bean-like testes in the


Figure 7
Bohm bristles on scape dome of male
(X900)
Figure 8. Close-up of Bohm bristles on scape
dome of female (X2667)


86


Figure 1. Beet armyworm moth, male


white reticulations on the epicranium. The width of
the first instar head capsule is .25 mm (n=60). Full
grown larvae measure from 30 to 35 mm.
Only the first instar larva was examined with the
scanning electron microscope and its description follows:
The 6 ocelli are arranged in a semi-circular position
and are unequal in size: the third ocellus is the largest
while the first and the sixth ocelli are smaller than the
others (Figure 60). Setae on the head are more pointed
than those on the body, with lengths varying from 0.02
to 0.08 mm. They are usually curved or bent near the tip
while the body setae are more or less straight and thicker.
The body setae are also inserted in a raised pinaculum
which has a much larger diameter and is navel-like (Figure
61), whereas those on the head have only a simple
peritreme (Figure 63). There are numerous tiny spicules
on the body evenly distributed almost everywhere except
on some transverse folds and the intersegmental positions
of the larva (Figure 62).
D. Chromosome Number
Chromosomes are more or less spherical (dot-like),
similar to those found in other Noctuids. Definitive
chromosome counts with photographic confirmation were
obtained from five male larvae and four adults. The
haploid chromosome number of the beet armyworm is n=31
(Figure 64, 65). A haploid set of 31 chromosomes is the




Figure 54. The female reproductive system:
A.
B.
C.
D.
E.
F.
G.
H.
I.
J.
K.
L.
bursa copulatrix
vaginal duct
vulva
ovaries
lateral oviduct
median oviduct
oviporus and anus (gonopore)
spermatheca (utriculus)
spermathecal duct
lower loop of ductus receptacul
accessory gland
reservoir of accessory gland


97
B. Egg
Eggs are oblong spheroid in shape and circular in
cross section, with a diameter of approximately o.42 mm.
They are greenish when oviposited, turn cream-colored
within a few hours and finally become dark just before
hatching due to the black color of the larval head. They
are laid in clusters of 5 to over 100 in a single layer
and are covered with whitish scales from the tip of the
female abdomen for the early masses of eggs. Masses of
eggs oviposited later are often not covered because the
female moth has lost almost all the setae at the abdominal
tip (Figure 57). The micropyle, located at the top, is
surrounded by a petal-like pattern with the number of
petals varying from 7 to 11 (Figure 58). The whole egg
is composed of many concave surfaces delineated by higher
r
ridges (Figure 58). Many tiny pores, called aeropyles,
can be seen distributed at the edges of the ridges at
1430X (Figure 59). These aeropyles play a principal
role in gas and moisture exchange (Hinton, 1969).
C. Larva
There are five larval instars and on occasion six.
The first instar larva is about 1 mm long with a whitish
body and black head. The body color is highly variable
from specimen to specimen in later instars, ranging from
light green to olivaceous to near black. The head becomes
lighter in color being brownish with a number of near-


94
L
3 mm
j


42
and 251y in males and females, respectively. Average
widths are 56 and 44y respectively (Figure 24).
There are two types of scales in zone 2. One type
is serrate, similar to those in zone 1 with 6 to 7 points
for males and 4 to 6 points for females. The length and
width of this type scale is 280 x 50y for males and 307 x 49y
for females. The second type consists of basal scales
which are interspersed under the serrate scales. These
scales are shorter and blunt at the tip (Figure 25), with
a slight inward taper. Average measurements of these scales
are 169 x 52y and 140 x 51y in males and females, respectively.
Covering scales in zone 3 are similar in both males
and females. They are blunt tipped, but there are sometimes
indentions in females (Figure 26). The ultrastructure is
shown in Figure 28. Measurements are 315 x 55y and
308 x 51y in males and females, respectively. There are
blunt basal scales interspersed under the covering scales
in males. Their measurements are 96 x 48y There is no
evidence of basal scales in females.
There is a sac-like structure (Figure 27) covered
with spine-like scales at the posterior base of zone 3
(where the forewing and hindwing are joined). A sexual
dimorphism was found with the scales smooth and larger
at their base in females (Figure 29) while the scales are
stronger and the diameter is about the same for the entire
length in males (Figure 30). The function of the sac-like


117
Srivastava, B. B. L. 1970. Studies on the nervous
parts, tracts and commissure in the brain of
Prodenia litura Fabr. (Lepidoptera: Noctuidae).
Acta.Anat. 74(2): 243-66.
1972 Nervous system of abdominal segments of
the larva of Prodenia litura (Lepidoptera: Noctuidae)
J. Georgia Entomol. Soc. 7(1): 37-50.
Srivastava, B. K. and L. M. L. Mathur. 1963. Morphology
of cephalic and prothoracic glands of the mature
larva of Prodenia litura Fabr. (Lepidoptera:
Noctuidae). Indian J. Entomol. 25: 116-22.
1964. Morphology and musculature of the head
capsule of mature larva of Prodenia litura Fabr.
(Lepidoptera: Noctuidae). Indian J. Entomol
26(1): 78-91.
Virkki, N. 1963. Gametogenesis in the sugarcane borer
moth, Diatraca saccharalis (F.) Crambidae. J.
Agr. Univ. Puerto Rico. 47(2): 102-37.
Wellso, S. G. and P. L. Adkisson. 1962. The morphology
of the reproductive system of the female pink boll-
worm moth, Pectinophora gossypiella Saunders. J.
Kansas Entomol. Soc. 35: 233-35.
Williams, J. L. 1948. Anatomie comparee des genitalia
internes de quatre especes representant quatre
genres et deux sousfamilles de Noctuidae (Lepidoptera
Rev. Franc. Lepid. 11: 238-50.
Wilson, J. W. 1932. Notes on the biology of Laphygma
exigua Hubner. Florida Entomol. 16: 33-39.
1934. The asparagus caterpillar: its life
story and control. Univ. Fla. Agr. Exp. Sta. Tech.
Bull. 271. 26p.
Wonfor, F. 1868. On certain butterfly scales,
characteristic of sex. Quart. J. Microbiol. Sci.
N. S. 8: 80-85, 9: 19-22, 426-428 (1869)
Yagi, N. 1954. Note of electron microscope research on
pterin pigment in the scales of pierid butterflies.
Annotations Zoologicae Japonenses, 27(3): 113-14.


ACKNOWLEDGMENTS
The author is greatly indebted to Dr. Dale H. Habeck
as chairman of the Supervisory Committee for his guidance,
criticisms, and valuable suggestions in carrying out the
work and organizing the material for this dissertation.
Further appreciation is expressed to Dr. Habeck for
supplying the laboratory and photographic supplies necessary
for this research.
Deep appreciation is expressed to Dr. Harvey L.
Cromroy, Departments of Entomology and Radiation Biophysics,
who has offered valuable assistance to the author.
The author wishes to express his gratitude to Mrs.
Thelma C. Carlysle for her aid with the use of the scanning
electron microscope, darkroom work, and the histological
slides. Grateful acknowledgment is given to Dr. Derrell
Chambers for providing facilities in the Insect Attractants,
Behavior and Basic Biology Research Laboratory, USDA,
Gainesville, and to Dr. Thomas C. Emmel for helping in the
chromosome study.
Special thanks are extended to Dr. Dale Habeck, Dr.
Harvey Cromroy, Dr. Milledge Murphey, Dr. Louis C. Kuitert
and Dr. James Soule who have taken the time to edit and
criticize this dissertation.
ii i


6
as well as notes on some other noctuids. However,
the only description of the sensilla on the beet
armyworm antenna was made by Jefferson et al (1970).
The first microscopic study on the organization
of the Lepidoptera wings was by Deschamps (1835) .
Bowerbank (1838) reported on the scale structure of
the wings of Lepidoptera. Wonfor (1869) studied certain
butterfly scales and gave some characteristics of sex.
The taxonomic value of the scales of the Lepidoptera
*
was reported by Kellogg (1894). Mayer (1896) gave
further details on the development of the wing scales
and their pigment in butterflies and moths. Kuznetsov
(1915) contributed an overall study on Lepidoptera scale
structure. Gentil (1935) studied in general the scale
arrangement of the wings of Lepidoptera with an optical
microscopy method. Since then, some researchers have
studied some genera in more detail. The use of the
transmission electron microscope on Morpho scales, (Gentil,
1942; Kinder and Suffert, 1943; Richards, 1944), showed
that ..iridescent colors were structural and resulted
from diffraction of light by ridges on the scale rather
than from pigments. Yagi (1954) found that in the genus
Colias (Lepidoptera: Pieridae) the yellow and/or orange
colors were not structural and disclosed the presence of
round and spindle-shaped aggregations of pigments.
Kolyer et al (1970) studied the ultrastructure of the
scales in Colias eurytheme and he found some variations


25


56


Figure 41. Scent glands located between VUIth
and IXth abdominal segments. Dark
color: sclerotized area


114
Callahan, P.S. and Thomas Cascio. 1963. Histology of
the reproductive tracts and transmission of sperm
in the corn earworm, Heliothis zea. Ann. Entomol.
Soc. Amer. 56(4): 535-56.
Callahan, P.S., E. F. Taschenberg, and T. Carlysle. 1968.
The scape and pedicel dome sensors a dielectric
aerial wave-guide on the antennae of night-flying
moths. Ann. Entomol. Soc. Amer. 61: 934-37.
Chatterjee, S. N. 1969. The identity of Spodoptera
mauritia acronyctoides, Guenee, S. pecten Guenee
and S. abyssinia Guenee (Lepidoptera: Noctuidae)
based on a comparative study of the male and female
genitalia. Proc. Nat. Inst. Sci. India part B.
Biol. Sci. 35(1): 45-52.
Chlodkovky, N. 1884. Uber die Hoden der Lepidoptera,
Zool Anz. 7: 564-8.
Deschamps, B. 1835. Recherches microscopiques sur
1'organisation des ailes des Lepidopteres. Ann.
Sci. Nat. 3: 111-37.
Emmel, Thomas C. 1969. Methods for studying the cb-.mosomes
of Lepidoptera. Res. Lepid. 7: 23-8 ("1968").
Fatzinger, C. W. 1970. Morphology of the reproductive
organs of Dioryctria abietella (Lepidoptera: Pyralidae
[Phycitinae]) Ann. Entomol. Soc. Amer. 63(5): 1256-62.
Gentil, K. 1935. Der Bau der Schillerschuppen von Papilio
paris. Entomol. Rundshau, 52: 230-32.
1942. Elektronmikroskopische untersuchung des
feinbaues schillernder leisten von Morpho-schuppen.
Zeitschrift fur Morphologie und Okologie der Tiere,
38(2): 345-55.
Griffith, P. 1968. Investigation of insect electromagnetic
communication. ERL Rep. No. 68-3. Electronic Res. Lab.,
Univ. Calif., Berkeley.
Gupta, Y. 1964. Chromosome studies in some Indian
Lepidoptera. Chromosoma 15: 540-561.
Hammad, S. M. 1961. The morphology and histology of the
sexual scent glands in certain female lepidopterous
moths. Bull. Soc. Entomol. Egypte 42: 471-82.
and H. J. Jarczyk. 1958. Contributions to the
biology and biochemistry of the cotton leafworm,
Prodenia litura Fabr. III. The morphology and histology
of the sexual scent glands in the female moth of
Prodenia litura Fabr. Bull. Soc. Entomol. Epvnte.
XLII: 253-61.


TABLE OF CONTENTS
ACKNOWLEDGMENTS iii.
LIST OF TABLES vi
LIST OF FIGURES vii
ABSTRACT xii
CHAPTER
I. INTRODUCTION 1
II. LITERATURE REVIEW 3
III.METHODS AND MATERIALS 8
A. Rearing 8
B. Gross Morphological Studies 8
C. Chromosome Number 9
D. Scanning Electron Microscope 10
IV. RESULTS AND DISCUSSION 12
A. Moth 12
1) Antennae 12
2) Wings 40
3) Scent Glands 69
4) Reproductive System 70
B. Egg 97
C. Larva 97
D. Chromosome Number 102
V. CONCLUSIONS 112
VI. LITERATURE CITED llo
VII. BIOGRAPHICAL SKETCH 118
v






14
diagonally across each segment cover the dorsal surface
-of the antenna. Slightly more than half of the antennal
circumference is covered with scales at the base of the
antenna. Less of the antennal circumference is covered
distally until only about one-third is covered with scales
near the tip.
Most sensilla are found on the ventral surface of
the flagellum (Figure 4, 5). At least six distinct kinds
of sensilla were recognized. Some of these can be clas
sified into subtypes. All dimensions given are means of
12 measurements (Table 2).
1) Bohm bristles (Figure 7, 8). The Bohm bristles are
spine-like sensilla found only on the scape and pedicel.
They taper more sharply than the sensilla chaetica of the
flagellum. Two types of Bohm bristles occur; more numerous
ones are short (type 1) and longer ones (type 2) which are
evenly dispersed among type 1 have a socket and sclerotized
ring at the base. Bohm bristles are longer in females,
their average length varying from 24-39y compared to 17-23y
in males.
On the scape, they are concentrated on 4 domes: two
large domes laterally, and two small ones, one ventral and
one dorsal. On the pedicel, they occur only on two lateral
domes near the intersegmental area between the pedicel and
the first flagellar segment.
2) Sensilla chaetica (Figure 6, 9). The sensilla chaetica
are blunt spines set in a membraneous socket on the flagellar


Figure 44. Ovipositor showing sensilla on
extreme tip (X133)
Figure 45. Close-up of ovipositor opening (X253)


Figure 5
Figure 6
Most distal segment of the antenna
showing sensors covering most of
the circumference (X1410)
Chaeticum and trichodea on segment
near base of antenna (X2926)


Ill


Figure 21. Dorsal forewing scales in zone 1
(X253)
Figure 22. Dorsal forewing covering and basal
scales in zone 2 (X253)


75
abdominal segment of S. exigua is modified with two lateral
plates which serve as an ovipostor (Figure 44-46). These
plates have three types of sensilla': trichodea, button
like, and sensory hairs (Figure 47). Scales are also
observed on the inside of the plates (Figure 46).
The male genital complex of Lepidoptera includes the
eighth, ninth, and tenth abdominal segment. The external
male genitalia in the dorsal view (Figure 48) consists
of the gnathos and 3 spine-like structures. The median
spine-like structure, common to most Lepidoptera, is
the uncus which articulates basally with the tegumen (a
structure shaped like a hood or inverted trough lying
dorsal of the anus). The paired spines articulate basally
with the vinculum which is a U-shaped sclerite derived
from the 9th abdominal sternite. Its arms articulate
dorsally with the tegumen and its caudal margin with the
harpes (or claspers). These two lateral hooks do not
occur in some other genera of Noctuidae i.e. Feltia
subterrnea or Heliothis zea These 3 spines apparently
help the male position the female and hold her during
copulation (Figure 48). The ventral view (Figure 49),
shows the underside of the tegumen and uncus including
the scale sockets on the tegumen. In Figure 50, the
claspers form a V with the uncus between. The claspers
are thickly clothed with scales which may have a sensory
function (Figure 51).


Figure 52. Sensilla and scales on outside of
the clasper; male genitalia (X1463)
Figure 53. Ultrastructure of scale inside of
clasper; male genitalia (X7182)


66


52


Figure 19. Fore- and hind-wing (dorsal) surface
showing zonal division for both male
and females (zone 1 shaded, zone 2
unshaded).


104


40
2) Wings
Wings can be differentiated into certain zones based
upon the types of scales found there. These zones do not
correspond with wing venation. Approximate zones for both
sexes and both wings (dorsal and ventral) are shown in
Figures 19 and 20. In general the zones are similar on
both wings dorsally and ventrally and in both sexes except
for the ventral surface of the forewing which will be
discussed later. Zone 1 usually takes up about the anterior
one-fourth of each wing and zone 2 takes up the remainder
of the wing. The third zone was the border consisting of
3 to 5 rows of scales.
Dorsal forewing: Scales found in zone 1 (Figure 21)
of both male and female moths gradually increase in
width from the shaft to the tip. They are serrate at the
tip with 3 to 6 points in the males and 4 to 6 in the
females. Average lengths are 292y and 280y in males and
females, respectively. Average width is the same (41y)
for both sexes. Pigmentation is more heavily concentrated
down the mid-line and the outer margin of the scale and
across the apex. The scales in the female are darker than
in the male.
There are two types of scales in zone 2. One type is
similar to those in zone 1 in that they gradually increase
in width from the base to the apex. The length and width
of this type scale is 262 x 47y for males and 276. x 56y for females
Scales are serrate at the tip with 5 to 6


70:
the orange scales have higher longitudinal ribs and the
cross ribs are consistently circular and accentuated when
viewed at 4400X (Figure 35). The gray or black scales
have relatively smooth, shallow grooves between the ribs
and the cross ribs have no regular pattern (Figure 36).
Preliminary research on the ultrastructure of the
scales at magnifications in excess of 4000X, revealed
differences that offer possibilities for further clas
sification of scale types. There are distinct differences
in the structure of the ribs and cross ribs. The groove
is smooth without perforations (Figure 37) or with
perforations in some scales (Figure 38). The groove in
others is perforated with numerous large openings (Figure
39). The cross ribs can be straight (Figure 39) or curved
(Figure 40). Another variation is found in border scales
on the forewing where every third or fourth rib is
thickened. Much more could be done on the subject of
ultrastructure of wing scales and a comparative study of

various families of moths could reveal some very interesting
and meaningful information on relationships throughout
the order.
3) Scent Glands
Scent glands are situated in the ventral intersegmental
area between the 8th and 9th abdominal segments. They belong
to type 2 with ventral sac (Amphipyrinae) compared to type 1
with a dorsal sac or fold (Plusiinae) and type 3 with a


ft
LIST OF FIGURES
Figure 1. Beet armyworm moth, male 21
Figure 2. Beet armyworm moth, female 23
Figure 3. Dorso-lateral view of antennal
segment showing convergence of
scale surface with sensory sur
face. Distal portion of antenna
with dorsal surface to the right
(X898) 25
Figure 4. Lateral view of the ventral
surface of the basal portion
of antenna (X7 05) 25
Figure 5. Most distal segment of the antenna
showing sensors covering most of
the circumference (X1410) 27
Figure 6. Chaeticum and trichodea on segment
near base of antenna (X2926) 27
Figure 7. Bohm bristles on scape dome of male
(X900) 2.9
Figure 8. Close-up of Bohm bristles on scape
dome of female (X2667) 29
Figure 9. Close-up of chaeticum on the antenna
(X7182) 31
Figure 10. Sensilla auricillica and button-like
sensor (X7049) 31
Figure 11. Close-up of chaeticum (X6835) 33
Figure 12. Short porous trichodea (X1540) ... 33
Figure 13. Long porous trichodea (X5060) 35
Figure 14. Long porous trichodea (X13,333) 35
Figure 15. Non-porous trichodea (X6835) 37
Vll


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19
female and consequently might indicate the reason for the
multiple rows of trichodea on the male which are much longer
than the regular ones, and which apparently serve as
pheromone receptors. The great lack of neuroelectrophysio-
logical information makes it impossible to assign reasons
for morphological arrangements of the sensilla and
consequently one can only conjecture about the placement
of certain sensilla on the antennae.
Table 2. Measurements and proposed functions of sensilla
on beet armyworm antenna.
Sensilla types
Proposed
function
k
Length y
Diameter
at base
Sensilla coeloconica
chemoreceptor
temp. § humidity
-
9.6
Sensilla auricillica
unknown
12
4.8
Sensilla styloconica
taste
15.6
7.2
Trichodea types 1, 2
pheromone receiver
chemoreceptor
17-29
1-2
Trichodea type 3
pheromone receiver
38-58
2-5
Trichodea type 4
((Xonly)
pheromone receiver
84-125
4-5
Chaetica cf
55-123
5-10
Chaetica ^
43-91
5-5.5
Bohm bristles ^
24-39
Bohm bristles &
17-23
* n=12


Figure 61. Microspines and setae on first instar
larva (X1596)
Figure 62. Spiracle of first instar larva (X1410)


Figure 9
Close-up of chaeticum on the antenna
(X7182)
Figure 10
Sensilla auricillica and button-like
sensor (X7049)


Figure 66. Bundles of sperms in testis (X 1197)
Figure 67. Two sperms among nucleus division
in testis (X1197)


35


LIST OF TABLES
Table 1. Comparison of antennal flagellar
segment length in beet armyworm 13
Table 2. Measurements and proposed functions
of sensilla on beet armyworm antenna. 19
Table 3. Measurements of female internal
reproductive organs and spermatophore 79
Table 4. Measurements of male internal
reproductive organs 80
vi


13
Jefferson et al. 1970. There was little difference in
the mean number of segments between the sexes but there
was some difference in the length and width of antennal
segments between male and female (Table 1).
Table 1. Comparison of antennal flagellar segment length
in beet armyworm (n=6 for each sex).
Length (y) Width (y)
Females
mean
range
mean
range
Proximal
segments
125.3
112-144
164.0
-114-180
Middle
segments
132.8
127-139
100.0
91.108
Distal
segments
88.8
84-91
63.2
57-72
Males
-
Proximal
segments
101.0
91-110
141.6
129-151
Middle
segments
122.7
111-132
114.7
96-140
Distal
segments
77.5
74-86
58.3
50-64
The basal segments of the antennae are short. The
segments elongate distally, reaching their greatest length
at about the midpoint of the antenna, then gradually de
creasing in length to the end. The diameter of the seg-
\
ments decreases progressively from the base to the end of
the antenna. All antennal segments of the male are shorter
than the comparable ones of the females (Table 1).
The dorsal surface of the flagellum is covered by
overlapping scales (Figure 3). Two rows of scales oriented




33


Figure 59. Egg surface showing aeropyles (pores)
on edge of ridges (X1430)
Figure 60. Ocelli and antenna of first instar
larva, dorso lateral view (X665)


LIST OF FIGURES (Continued)
Figure
31.
Dorsal hindwing: scales in zone
1 and piliform scales (X253) ....
. 60
Figure
32.
Dorsal hindwing: scales in zone
2 (X253)
. 60
Figure
33.
Ventral hindwing: scales in zone
1 (X253)
. 62
Figure
34.
Ventral hindwing: scales in zone
2 (X253)
. 62
Figure
35.
Ultrastructure of orange scale
showing high longitudinal ribs
and circular cross-ribs (X4985) .
. 64
Figure
36.
Ultrastructure of gray scale showing
shallow grooves and irregularly
patterned cross-ribs (X5852) ....
. 64
Figure
37.
Ultrastructure of scale on ventral
hindwing in zone 2 showing smooth
groove without perforations (X4985)
. 66
Figure
38.
Ultrastructure of border scale on
ventral hindwing showing smooth
groove with perforations (X5852) .
. 66
Figure
39.
Ultrastructure of the scale on dorsal
forewing in zone 2 showing straight
cross-ribs (X4985)
. 68
Figure
40.
Ultrastructure of scale on dorsal
hindwing in zone 2 showing curved
cross-ribs (X4985) .
. 68
Figure
41.
Scent glands located between VUIth
and IXth abdominal segments. Dark
color: sclerotized area
. 72
Figure
42.
The scent gland in the intersegmental
area between the 9th sternite and
the 8th sternite ,
Figure
43.
Close-up showing wavy surface of
the scent gland and glandular
cells underneath
Figure
44.
Ovipositor showing sensilla on extreme
tip (X133)
IX


116
Mathur, L. M. L. 1969. Morphology of the nervous system
of adult Prodenia litura. Ann. Entomol. Soc. Amer.
62(3): 525-29.
Mayer, A. 1896. The development of the wing scales and
their pigment in butterflies and moths. Bull. Mus.
Comp. Zool. Harvard, XXIX, 209-236.
Murad, H. 1969. Musculature of the sucking pump of
Spodoptera mauritia Boisduval (Lepidoptera:
Noctuidae). Proc. Nat. Acad. Sci. India Sect.
B (Biol. Sci.) 37(2): 135-58.
Musgrave, A. J. 1937. Histology of the male and female
reproductive organs of Ephestia kuhniella.
Proc. Zool. Soc. London (B), 107: 337-64.
Norris, M. J. 1932. Contributions towards the study of
insect fertility. I. The structure and operation
of the reproductive organs of the genera Ephestia
and Plodia. Proc. Zool. Soc. London 3: 595-611.
1933. Contributions towards the study of
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(Lepidoptera: Phycitidae). Proc. Zool. Soc. London
4: 903-34.
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fumiferana. Can. Entomol. 102: 404-14.
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(stereoscopic electron micrographs of Morpho
cypris iridescent scales). Entomol. News, 55(7):
190-93.
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Pol. 17(4): 315-22.


43
structure is not known but it may minimize friction between
the wings and facilitate the movements of both wings.
Dorsal hindwing: There are two zones in both males
and females. Zone 1 covers the anterior one-fifth of the
hindwing and zone 2 takes up the remainder. The anterior
*
and posterior edges of the hindwing have many piliform
(hair-like) scales varying from 600 to 1200y long and
3.5 to 6y wide. Only the males have these piliform scales
interspersed in both zones 1 and 2, (Figure 31), there
are none in the females in either zone. Covering scales
are mostly light gray or white except the scales on the
veins have darker pigmentation.
The covering scales in zone 1 are serrate with 2 to 5
points in males and 4 to 6 points in females. Pigmentation
in zone 1 is darker than in zone 2. The measurements are
228 x 52y for males and 252 x 58y for females. The basal
scales are blunt tipped and interspersed underneath the
covering scales. Average measurements are 138 x 50y .
The covering scales in zone 2 are serrate with 2 to 4
points for males and 4 to 6 points for females (Figure 32).
Their average measurements are 220 x 55y (maTe^) and 238 x 53y
(females). White scales are predominant. There is no pig
mentation in the females compared to a slightly darker pig
mentation in the males. Blunt tipped basal scales are
interspersed beneath the serrate scales. Their average
measurements are 170 x 48y .
The border scales are serrate with 3 to 5 points in the
males and 4 to 5 points in the females. The shaft is one half


Figure 56. The male reproductive system:
4
A. testis
B. seminal vesicle
C. vas deferens
D. accessory gland
E. ductus ejaculatorius duplex
F. ductus ejaculatorius simplex
G. aedeagus


LIST OF FIGURES (Continued)
Figure 16.
Sensilla coeloconica (X6650) 37
Figure 17.
Sensilla auricillica (X6835) 39
Figure 18.
Sensilla styloconica (X4430) 39
Figure 19.
Fore- and hind-wing (dorsal) sur-
face showing zonal division for
both males and females (zone 1
shaded, zone 2 unshaded) 46
Figure 20.
Upper: zonal division of forewing
(ventral surface) in males
Middle: zonal division of forewing
(ventral surface) in females
Lower: zonal division of hindwing
(ventral surface in both males
and females 48
Figure 21.
Dorsal forewing scales in zone 1
(X253) 50
Figure 22.
Dorsal forewing covering and basal
scales in zone 2 (X253) 50
Figure 23.
Border scales on dorsal forewing
(X253) 52
Figure 24.
Scales on ventral forewing in zone 1
(X253) 5:2
Figure 25.
Basal scales and covering scales on
ventral forewing in zone 2 (X253). ... 54
Figure 26.
Scales on ventral forewing in zone 3
(X253) 54
Figure 27.
Spine-like scales on posterior base
of ventral forewing on sac-like
structure and regular scales in
zone 3 (X226) 56
Figure 28.
Ultrastructure of scales in zone 3
(X6317) / 56
Figure 29.
Scales on anterior anal area of the
forewing (female, ventral) (X4522) ... 58
Figure 30.
Scales on anterior anal area of the
forewing (male, ventral ) (X2660) ... 58
viii
. 58


To my wife, Ton-Nu Thanh-Chau
and my children,
Ngo Bao, Ngo Quynh, Ngo Anh, Ngo Anh-Thu.


Figure 42. The scent gland in the intersegmental
area between the 9th sternite (on the
right) and the 8th sternite (on the
left). Tip of abdomen at top of pic
ture
Figure 43. Close-up showing wavy surface of the
scent gland and glandular cells under
neath. 8th abdominal sternite visible
on the left. Tip of abdomen at top
of picture


54


10
was allowed to stand for about 20 minutes. The stained
testes were next covered with a coverslip and the pre
paration was squashed first by thumb pressure between
two pieces of blotting paper and then transferred to a

laboratory press to exert uniform pressure and spread
the preparation. The perimeter of the coverslip was
then sealed with clear lacquer. Mounted slides were
stored at 20 F for later reference.
Slides were inspected with a Zeiss Research
Microscope Standard WL fitted with 25X and 40X plan
apochromatic flat field objectives and automatic
camera, and a Watson photo automatic phase contrast
microscope "Hilux 70 PH" fitted with 40X planparo and
90X Fluorite contrast objectives and automatic camera.
An oil immersion planapo 100X objective was used for
critical observations.
D. Scanning Electron Microscope Studies
Eggs, first instar larva, antenna, wing scales,
and the external reproductive organs of the adults were
observed under the scanning electron microscope. Attention
was primarily focused on sensory structures. The scanning
electron microscope Cambridge Mark Il-A was used for the
microstructure of the insect through the courtesy of the
USDA in Gainesville and with the aid of Mrs. Thelma C.
Carlysle. Range of magnification used was x35 to xl4,000.


two zones in forewing (dorsal), hindwing (dorsal and
ventral), and three zones in forewing (ventral). Scent
glands are present in the ventral intersegmental area
between the 8th and 9th abdominal segments. Three types
of sensilla are found on the lateral plates forming
the ovipositor. The 9th abdominal segment of the male
has a curved uncus and two lateral hooks arising from
the claspers. Externally, there are many more scales
and very few sensilla on the male genitalia compared
to the female. The female ovary is composed of four
ovarioles and development is panoistic.
The egg chorion around the micropyle is shaped
petal-like with 7-11 lobes. Many tiny aeropyles occur
on the edge of egg ridges.
The first instar larva is covered with microspines.
Head setae tend to be sharp, curved and without raised
pinaculum while body setae are straight and blunt tipped
with pinaculum.
The haploid chromosome number for this species was
determined to be n=31.
XI 3 i