• TABLE OF CONTENTS
HIDE
 Title Page
 Acknowledgement
 Table of Contents
 List of Tables
 List of Figures
 Introduction
 The history
 Distribution of larval food...
 Populations of Aaraulis vanillae...
 The fall migration
 Orientation experiments
 Discussion and conclusions
 Summary
 Bibliography
 Biographical sketch














Title: Biology and migratory behavior of Agraulis vanillae (L.) (Lepidoptera, Nymphalidae) /
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 Material Information
Title: Biology and migratory behavior of Agraulis vanillae (L.) (Lepidoptera, Nymphalidae) /
Physical Description: viii, 97 leaves : ill. ; 28 cm.
Language: English
Creator: Arbogast, Richard Terrance, 1937-
Publication Date: 1965
Copyright Date: 1965
 Subjects
Subject: Lepidoptera   ( lcsh )
Beneficial insects   ( lcsh )
Insect pests   ( lcsh )
Entomology and Nematology thesis Ph. D
Dissertations, Academic -- Entomology and Nematology -- UF
Genre: bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Thesis: Thesis (Ph. D.)--University of Florida, 1965.
Bibliography: Includes bibliographical references (leaves 93-96).
Additional Physical Form: Also available on World Wide Web
Statement of Responsibility: by Richard Terrance Arbogast.
General Note: Typescript.
General Note: Vita.
 Record Information
Bibliographic ID: UF00097891
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: alephbibnum - 000432036
oclc - 37517404
notis - ACJ1540

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Table of Contents
    Title Page
        Page i
        Page i-a
    Acknowledgement
        Page ii
    Table of Contents
        Page iii
        Page iv
    List of Tables
        Page v
    List of Figures
        Page vi
        Page vii
        Page viii
    Introduction
        Page 1
        Page 2
        Page 3
        Page 4
    The history
        Page 5
        Page 6
        Page 7
        Page 8
        Page 9
        Page 10
        Page 11
        Page 12
        Page 13
        Page 14
        Page 15
        Page 16
        Page 17
        Page 18
        Page 19
        Page 20
        Page 21
        Page 22
        Page 23
        Page 24
        Page 25
    Distribution of larval food plants
        Page 26
    Populations of Aaraulis vanillae in the vicinity of Gainesville, Florida
        Page 27
        Page 28
        Page 29
        Page 30
        Page 31
        Page 32
        Page 33
        Page 34
        Page 35
    The fall migration
        Page 36
        Page 37
        Page 38
        Page 39
        Page 40
        Page 41
        Page 42
        Page 43
        Page 44
        Page 45
        Page 46
        Page 47
        Page 48
        Page 49
        Page 50
        Page 51
        Page 52
        Page 53
        Page 54
        Page 55
        Page 56
        Page 57
    Orientation experiments
        Page 58
        Page 59
        Page 60
        Page 61
        Page 62
        Page 63
        Page 64
        Page 65
        Page 66
        Page 67
        Page 68
        Page 69
        Page 70
        Page 71
        Page 72
        Page 73
        Page 74
        Page 75
        Page 76
        Page 77
        Page 78
        Page 79
        Page 80
        Page 81
        Page 82
        Page 83
    Discussion and conclusions
        Page 84
        Page 85
        Page 86
        Page 87
        Page 88
        Page 89
        Page 90
    Summary
        Page 91
        Page 92
    Bibliography
        Page 93
        Page 94
        Page 95
        Page 96
    Biographical sketch
        Page 97
        Page 98
        Page 99
Full Text







BIOLOGY AND MIGRATORY BEHAVIOR

OF AGRAULIS VANILLA (L.)

(LEPIDOPTERA, NYMPHALIDAE)
















By
RICHARD TERRANCE ARBOGAST


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
August, 1965












ACKNOWLEDGMENTS


The writer wishes to express his thanks to the numerous

persons who contributed their assistance and suggestions during

the course of his graduate study.

Special thanks are due Dr. T. J. Walker, who first

a--oused the author's interest in insect migration and who served

as Chairman of the Supervisory Committee. His encouragement and

many suggestions during the conduction of the research and prep-

aration of the manuscript were invaluable contributions.

Much appreciation is also expressed to Dr. L. A. Hetrick,

Dr. D. B. Ward, Dr. D. H. Habeck, and Dr. E. G. F. Sauer who

served as members of the Supervisory Committee, and to Dr. C. D.

Monk who was originally a member of the committee.

Thanks also go to Dr. J. T. Creighton, former Head of

the Department of Entomology, for his assistance during the course

of the author's graduate work and to Mr. J. P. Ahrano for permis-

sion to use the field in which observations of the migration were

made.

Finally, the writer would like to express his appreciation

to his wife for her patience during his years of graduate study

and for her assistancee in the preparation of this manuscript.















TABLE OF CONTENTS


Page


ACKNCWLEDGMENTS . . . . . . . .

LIST OF TA3LES . . . . . . . . .

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

INTRODUCTION . . . . . . . . .

LIFE HISTORY . . . . . . . . .
Methods and Materials . . . . .
Rate of development . . . . .
Longevity of the adults . . . .
Reproductive development of the female .
Behavior of adults and larvae. . . .
The Egg and Oviposition . . . . .
The Larva . . . . . . ... .
The Pupa . . . .. . . . . .
The Adult . . . . . . ... .
Emergence . . .. . . . . .
Sex ratio . . . . . .. .
Reproductive development of the female
Mating behavior . . . . ...
Longevity,of the adults . . . .

DISTRIBUTION OF LARVAL FOOD PLANTS . . . .

POPULATIONS OF Anraulis vanilla IN THE VICINITY
GAINES3V LLE, FLORIDA . . . . . . .
Description of Observed Breeding Areas . .
Fluctuations in the Observed Populations .

THE FALL MIGRATION . . . . . . .
Methods and Materials . . . . .
Observational setup . . . . .
m father observations . . .....
Sp!ed and direction of flight. . . .
DCnsity of the migration . . . .
Reproductive maturity of the females and
Description of the Migration . . . .
Characteristics of the migratory flight.
Variations in migration density. . .
Reproductive maturity of the females and


OF













sex




sex


iii


ratio




ratio






Page

ORIENTATION EXPERIMENTS. . . . . . . . . 58
Introduction . . . . . . . . . 53
Methods and Materials. . . . . . . . . 59
Results . . . . . . . . . . 66

DISCUSSTCN AND CONCLUSIONS . . . . . . ... 84

SU~vI ARY. . . . . . . . . . . ... . 91

LITERATURE CITED . . . . . . . . . . 93

BIOGRAPHICAL SKETCH ................... 97















LIST OF TABLES


Table

1.






3.



4.



5.



6.

7.


Observed Number of Eggs and Larvae in Area 1
(.9o4-05) . . . . . . . . .

C..., ,rved Number of Eggs and Larvae in Area 2
( s19u4-65) . . . . . . . . . ..

O"' ,rved Number of Eggs and Larvae in Area 3
(1 .4-65 ). . . . . . . . . . .

OCis(rved Number of Eggs and Larvae in Area 4
(19u4-65) . . . . . . . . .

Density of Migration and Weather Observed 1300-
1400 EST (1964) . . . . . . . .

Tirme of Beginning of Migration on Various Days

Migration Densities Observed at Various Times on
September 23, 1964 . . . . . . . .


Page


S 30



S 31



S 32



S 33



S 55

56



56














LIST OF FIGURES


Figure Page

1. Fourth instars of Agraulis vanilla nigrior
Michener. . . . . . . . . . ... 11

2. Fifth instar of Agraulis vanilla nigrior Michener. 12

3. Feeding rhythms of fifth instars. . . . . 15

4. Duration of the various instars at 23-240 C. (left)
and at 28.5-29.50 C. (right). . . . . . 16

5. Dorsal view of pupa of Agraulis vanilla nigrior
Michener. . . . . . . . . . .. 18

6. Lateral view of pupa of Agraulis vanilla nigrior
Michener . . . . . . . . . .. 19

7. Duration of pupa at 23-24 C. . . . . .. 20

8. Duration of pupa at 28.5-29.50 C. . . . .. .20

9. Time of emergence of the adult. .... . .. . 21

10. Recently emerged adult of ANraulis vanilla nigrior
Michener hanging from the pupal skin. . . . 23

11. Breeding areas in the vicinity of Gainesville,
Florida . . . . . . . . . . . 28

12. Setup for observing migrations. . . . . ... 37

13. Wind vane and anemometer used in migration studies. 38

14. Wind speed and direction dials used in migration
studies . . . . . . . . ... . . 39

15. Wind vane and anemometer mounted on tripod for
observations. . . . . . . . . .. .41

16. Convention used in measuring angles between track
and wind direction (6) and between track and
course (). . . . . . . . . ... .. 43









17. Tracks of migrants observed during the fall of
1963 (A) and 1964 (B) . . . . . . ... 47

18. Tracks of migrants observed at various times of day
on September 23, 1964 . . . . . . . 48

19. Tracks of migrants and mean wind speed and direction
observed between 1300 and 1400 EST on various days
in the fall of 1964 . . ... . . . . 49

20. Ground speed of migrants flying in calm air . . 51

21. Ground speed of migrants flying against a head wind
of 1-5 miles per hour (A) and with a tail wind of
1-4 miles per hour (B). . . . . . . ... 52

22. Air speed of migrants flying against a head wind of
1-5 miles per hour (A) and with a tail wind of 1-4
miles per hour (B). . . . . . . . . 53

23. Cage used for orientation tests . . . ... .61

24. Cutaway view of controlled photoperiod cabinet used
in clock resetting experiments. . . . . .. .65

25. Orientation of Individual A when tested between
0930 and 1030 EST,November 6, 1964, without reset-
ting the internal clock . . . . . ... 69

26. Orientation of Individual A when tested between
1440 and 1540 EST, November 6, 1964, without re-
setting the internal clock. . . . . . ... 70

27. Orientation of Individual B when tested between
0950 and 1050 EST, October 30, 1964, without reset-
ting the internal clock . . . . . ... 71

28. Orientation of Individual B when tested between
1410 and 1510 EST, November 5, 1964, without reset-
ting the internal clock . . . . . ... 72

29. Orientation of Individual C when tested between
1240 and 1340 EST, November 5, 1964, without reset-
ting the internal clock . . . . ... ... 73

30. Orientation of Individual D when tested between
1510 and 1610 EST, November 5, 1964, without reset-
ting the internal clock . . . . . ... 74

31. Orientation of Individual D when tested between
1350 and 1450 EST, November 10, 1964, after setting
the internal clock back 6 hours (5 days in out-of-
phase cycle) . . . . . . . . . 75


Figure


Page







Figure


32. Orientation of Individual D when tested between
1310 and 1410 EST, November 11, 1964, after setting
the internal clock back 6 hours (6 days in out-of-
phase cycle). . . . . . . . . . 76

33. Orientation of Individual E when tested between
1030 and 1130 EST, November 9, 1964, without re-
setting the internal clock. . . . . . ... 77

34. Orientation of Individual E when tested between
1240 and 1340 EST, November 17, 1964, after setting
the internal clock back 6 hours (8 days in out-of-
phase cycle). . . . . . . . . . 78

35. Orientation of Individual F when tested between
0930 and 1030 EST, November 9, 1964, without re-
setting the internal clock. . . . . . ... 79

36. Orientation of Individual F when tested between
1430 and 1530 EST, November 16, 1964, after setting
the internal clock back 6 hours (7 days in out-of-
phase cycle . . . . . . . ... . . 80

37. Orientation of Individual G when tested between
1430 and 1530 EST, October 18, 1964, after setting
the internal clock back 6 hours (5 days in out-of-
phase cycle). . . . . . . . . .. .81

38. Orientation of Individual H when tested between
1530 and 1630 EST, October 20, 1964, after setting
the internal clock back 6 hours (3 days in out-of-
phase cycle) . . . . . . . . . . 82

39. Orientation of Individual I when tested between
1430 and 1530 EST, October 23, 1964, after setting
the internal clock back 6 hours (4 days in out-of-
phase cycle) . . . . . . . . . . 83


viii


Page














INTRODUCTION


Migration has been defined by Schneider (1962) as a

prolonged escape movement in which there is a tendency to main-

tain a constant direction and which results in the permanent or

periodical abandonment of a habitat. Migration can be classi-

fied as dispersive, contractive, or collective according to the

spatial effect. Many insects migrate in this sense, and numerous

accounts of their migrations can be found in the literature. Re-

cent reviews of insect migration have been published by Schneider

(1962) and Williams (1957, 1958).

In most of the migratory insects which have been care-

fully studied, the migratory direction is determined largely by

the prevailing wind. Swarms of the desert locust (Schistocerca

gregaria Forsk.) are carried downwind, and since the winds in

the lower few thousand feet of the atmosphere may be regarded

ultimately as blowing from areas of high pressure to areas of

low pressure, the downwind displacement results in movement into

areas of low pressure where abundant rainfall produces conditions

favorable for the reproduction of the locust (Rainey, 1951). The

migratory direction of the coccinellid Hippod,-.ia convergens

Gu6rin-Meneville in California is determined by the prevailing

winds at its flight level (Hagen, 1962). In the summer,.the

prevailing winds at this level are from the low lands toward





2

the mountains where aggregation occurs, and in the winter, they

are from the mountains to the low lands. The mosquito Aedos

taeniorhynchus Wiedemann migrates downwind (Provost, 1952,

1957).

In contrast to this, many migrating butterflies main-

tain, over long distances, a constant direction which is in-

fluenced little by wind, topography, or time of day (Williams,

1958). The determination of migratory direction appears to be

under the control of the insect itself, but the nature of the

underlying orientation mechanism has remained obscure. Only

two migratory butterflies have been studied in great detail

(Nielsen and Nielsen, 1950; Nielsen, 1961; Urquhart, 1960),

and these studies did not include an investigation of the

orientation mechanism. Recent work on the orientation of other

animals has suggested new approaches to this problem. (For

references, see Long Island Biological Association, 1960.) The

purpose of the research reported here, was to study the migra-

tory behavior of the gulf fritillary, Agraulis vanilla (L.),

against the background of its general biology and to investigate

the nature of the orientation mechanism involved in maintaining

the migratory direction.

The gulf fritillary is a member of the essentially neo-

tropical nymphalid subfamily Heliconiiae. Michener (1942) recog-

nizes eight subspecies as follows:

Agraulis vanilla vanilla (Linnaeus) occurs in northern

South America, Panama, and the southernmost of the Lesser

Antilles.




3

Agraulis vanilla insularis Maynard ranges throughout

the Bahamas and the Antilles except for the southern-

most Lesser Antilles.

Agraulis vanilla maculosa (Stichel) is found in northern

Argentina, Paraguay, southern Brazil, and Chile.

Aoraulis vanilla forbesi Michener occurs in the coastal

region of Peru.

Agraulis vanilla galapagensis Holland is restricted to

the Galapagos Islands.

Agraulis vanilla lucinia C. and R. Felder occurs on the

eastern side of the Andes in Ecuador, Peru, and Brazil.

Agraulis vanilla incarnata (Riley) is occasionally

found as far north as British Columbia but more com-

monly occurs in southwestern United States, Mexico,

and Central America.

Agraulis vanilla nigrior Michener is the subspecies of

southeastern United States but is occasionally found as

far north as New York.

The migratory habit has evolved in at least two of these sub-

species. Definite migrations of A. v. niorior to the north in

the spring and to the south in the fall have been observed in

Florida (Williams, 1958). Hayward (1962) reported an eastward

migration of A. v. maculosa at Tucaman, Argentina, on January

7, 1961. The research reported here was restricted to A. v.

niorior. This form intergrades with A. v. incarnata in Texas

and thence southward but is distinct from A. v. insularis.




4

The early stages of A. v. nigrior were described long

ago (Edwards, 1880; Scudder, 1889), but no detailed studies of

its biology have been made. More recently, detailed descrip-

tions of the early stages of A. v. vanilla have been published

(Beebe, Crane, and Fleming, 1960) and certain details of the

adult morphology have been described by Emsley (1963). The

biology and behavior of the larvae, pupae, and emerging adults

of A. v. vanilla were discussed by Alexander (1961a, 1961b)

and compared with those of other members of the subfamily

occurring in Trinidad.















LIFE HISTORY


Methods and Materials


Rate of development

Rearing to determine the rate of development was ini-

tiated with eggs obtained from females which had mated in cages.

These cages were 14 inches square and 24 inches high with sides

of aluminum screen and top and botton of 1 inch plywood. A 9

inch square opening in the top covered with a plate of glass

served as a door. One or more males and one or more females

which had been reared in captivity from larvae were confined

in a cage and placed outdoors in direct sunshine. Mating was

obtained in this manner using males 1-3 days after emergence

and females 0-3 days after emergence. Mating occurred in

both the morning and the afternoon and usually within 2 hours

after the butterflies were placed in the cage. Occasionally

no mating occurred even when the butterflies were left in the

cage all day, but frequently the same butterflies would mate

when placed in the cage the next day.

One to 3 days after mating, the females were confined

individually with cuttings of Passiflora incarnata L. This

was accomplished either by introducing a jar of water containing

the cuttings into the mating cage or by placing a cheesecloth

bag over cuttings contained in a flower pot full of damp sand

5





6

and then confining the butterfly in the bag. The latter

method was the most satisfactory. The confined butterflies

deposited many eggs on the side of the cage or on the cheese-

cloth bag. It was difficult to remove the eggs from the side

of the cage without damaging them, but those deposited on the

cheesecloth could be removed by cutting out the piece of material

to which they were attached.

The captive butterflies were fed once a day on sugar

water of variable concentration. A cotton ball was saturated

with the solution and placed in a small dish containing addi-

tional solution. The butterfly to be fed was grasped by the

wings and its tarsi touched to the cotton ball. Usually this

caused the butterfly to extend its proboscis and begin feeding.

Butterflies which refused to feed when touched to the cotton

ball could often be induced to feed by uncoiling the proboscis

and inserting its tip in the sugar water. Once feeding began,

the butterflies remained quietly on the cotton ball until

feeding was completed.

The time required to complete each stage of development

at each of two constant temperatures was determined by rearing

the insects in a constant temperature cabinet. In one case, the

temperature in the cabinet was maintained at 23-240 C. and in

the other case at 28.5-29.50 C. To determine the time required

for the eggs to hatch, 1-7 hour old eggs were placed in the cab-

inet in a covered petri dish and checked once a day for hatching.

To determine the duration of the remaining stages, the insects

were reared individually from egg to adult in pint fruit jars.




7

The caterpillars were kept supplied with one or two leaves of

the food plant. Each individual was examined once a day and

the dates of hatching, molting, pupation, and emergence were

recorded.

The larvae suspended for pupation from the lids of the

jars or from the point just below the neck where the sides

curve inward. In both cases the point of attachment was too

smooth and many of the chrysalides fell. This difficulty was

overcome by placing a piece of coarse-textured paper (toweling)

beneath the lid and inserting a screen cylinder which extended

from the bottom to the top of the jar. The larvae crawled up

the cylinder and suspended successfully from the paper.

Longevity of the adults

In order to gain some idea of the adult life span,

butterflies which had been reared from eggs in pint fruit

jars at a temperature of 23-240 C. were confined individually

in cubic screen cages 4 inches on a side and left in the con-

stant temperature cabinet at the same temperature. They were

fed daily as described above.

Reproductive development of the female

The elapsed time between the emergence of a female and

the maturation of the eggs in the ovaries was determined. For

this purpose, larvae in various stages of development obtained

from the field and from eggs laid by females in'captivity were

reared together on food plant cuttings in screen cages in a

greenhouse. The larvae were crowded but were kept abundantly

supplied with food, and the adults which were produced were of




8

normal size. When the adults began to emerge, it became

apparent that all emergences occurred during the morning, so

the cages were checked each day at 1 hour intervals between

0600 and 1200 Eastern Standard Time. Each time, all the but-

terflies that had emerged during the preceding hour were re-

moved and the time of emergence recorded as the time midway

between the last two checks. Thus the time of emergence re-

corded for each individual was accurate within + 30 minutes.

The females were confined in pint fruit jars with screen lids

and left in the greenhouse for periods of 0-48 hours with 6

hour increments. They were then preserved by injecting them

with 10 per cent formalin and placing them in 3 per cent forma-

lin. The preserved butterflies were dissected and the ovaries

examined.

Behavior of adults and larvae

The behavior of larvae of all stages and of adults was

observed in the field and in screen cages. In order to observe

the manner in which periods of larval feeding alternate with

periods of rest and walking, fifth instars were brought into

the laboratory from the field, and each was placed on a bunch

of food plant cuttings in a screen cage. The larvae were

observed for 4 hours, and the times at which feeding began and

ended were recorded for each individual. These observations

were made in the afternoon of a cloudy day, and the cages were

located in front of a southwest window. The sun occasionally

shown through the clouds, and as a result, the light intensity

in the cages varied considerably. However, there was no cor-

relation between feeding activity and the light intensity.








The Eoa and Cviposition


The larvae feed upon Passiflora incarnata and probably

other plants of the genus, and the females oviposit upon and

in the vicinity of these plants. Ovipositing females fly low

over and through the vegetation, frequently pausing to hover

about individual plants. When the butterfly contacts the larval

food plant, it alights and deposits an egg. Actual contact with

the plant seems to be essential for the release of oviposition.

Mated females confined with food plant cuttings deposited an

egg only after actually touching the cuttings. Mated females

confined without cuttings did not oviposit. The stimulus which

releases the act of oviposition is probably provided by a

chemical which is characteristic of this genus of plants and

which is detected by gustatory organs in the tarsi or antennae

of the butterfly.

The position of the egg depends upon where the female

is able to gain a foothold after contacting the food plant.

Most eggs are deposited upon the upper surfaces of the leaves,

but some are deposited on the undersurfaces, stems, tendrils,

buds, and nearby objects. The butterfly curves the abdomen

ventrad until the oviducal pore contacts the object upon which

it has alighted, whereupon it deposits an egg. In this process,

the tip of the abdomen may be turned through more than 270

degrees. A female which lands on a leaf surface near the margin

of the leaf often curves the abdomen around the margin and de-

posits an egg on the opposite surface. It was noted previously





10

that females confined in cages with food plant cuttings deposit

many of their eggs on the side of the cage. This results from

the fact that the butterflies frequently land on the side of

the cage after fluttering about and coming in contact with the

cuttings. Ovipositing females were observed on a small plant-

ing of P. incarnata along the side of a building. Frequently

they would strike the side of the building and alight after

coming in contact with the plants. Each time this occurred,

they deposited an egg on the side of the building.

Observations of females in the field and in cages

indicate that there is always a period of flight after the

deposition of each egg. Several eggs were often found on the

same leaf, but this was probably the result of several visits.

In some cases, this was borne out by the fact that some of the

eggs were yellow, while others were reddish brown (see follow-

ing paragraph). This behavior distributes the eggs more evenly

over the available food supply. Furthermore, larvae in captiv-

ity were observed chewing into unhatched eggs, even in the pres-

ence of abundant food. The spacing of the eggs brought about by

the egg laying behavior of the female reduces losses of this sort.

The eggs are yellow when deposited, but become reddish

brown within 24 hours. Thirty-nine eggs kept at a temperature

of 23-24 C. hatched on the fifth day. Thirteen eggs kept at

a temperature of 28.5-29.50 C. hatched on the third day.


The Larva

The larva is illustrated in Figures 1 and 2.












I II1
"i~


-4


'iure 1. Fourth instars of s v.. iI _























e


Figure 2.
Michener.


Fifth instar of Agraulis vanilla nigrior





13

Upon hatching, the young larva consumes the ecgshcll

before beginning to feed upon the food plant, and newly hatched

larvae were frequently observed eating unhatched eggs which

they happened to encounter, even in the presence of abundant

food. The caterpillars feed mainly upon the leaves, but when

food becomes scarce, they feed upon the exterior portions of

the buds and fruit and strip the epidermis and cortex from the

stems. The first three instars generally feed away from the

leaf margins. Newly hatched larvae feeding upon thick tough

leaves eat only the epidermal cells of one surface and the

mesophyll cells, leaving the epidermis of the opposite surface

intact. Newly hatched larvae feeding upon thin tender leaves

and older larvae in general cut holes completely through the

leaves. The two final instars feed at the leaf margins. When

ample food is available, the portion of a leaf which is eaten

before it is abandoned varies considerably. The petioles are

almost always left but may be eaten, at least in part, when

food becomes scarce. Larvae were never observed eating one

another, even when kept in crowded cages without food. In tvo

instances, however, larvae kept under these conditions were

observed eating chrysalides.

Alexander (1961a) studied the feeding rhythms of 10

species of heliconiine butterflies in Trinidad, including

Agraulis vanilla vanilla (L.) and found that feeding periods

of about 20-30 minutes alternate with rest periods of similar

duration. Four fifth instars of Aoraulis vanilla nin ior

Michener observed feeding in the laboratory showed a similar





14

feeding rhythm. Feeding periods of about 10-60 minutes alter-

nated with periods of rest and walking of about 10-90 minutes

(Figure 3).

Frequently a larva cuts a girdle 2-3 mm. wide around

a stem. This girdle extends only through the epidermis and

cortex and does not kill the plant. Larvae were observed cut-

ting these girdles many times in the field and in cages, and

large numbers of plants-were found with healed wounds of this

kind. In one case which was timed, girdling of the stem re-

quired 10 minutes (Figure 3D). Alexander (1961a) found similar

behavior in the larvae of severalheliconiine butterflies but

apparently not in the larvae of A. v. vanilla. The caterpillars

of Heliconius melpomene (L.) and H. ricini (L.) chew furrows

across the midribs of leaves, while the caterpillars of Dryas

julia (Fabr.) and Dryadula phaetusa (L.) cut narrow channels

from the margins to the midribs. In all cases this behavior

is exhibited during a rest period and it is therefore unlikely

that the material is eaten solely for its nutritive value.

Alexander suggested that the furrowing and channeling behavior

might be a form of territory marking. Perhaps the girdling

behavior of A. v. nigrior also represents territory marking,

but no evidence was obtained to either prove or disprove this

hypothesis.

The rate of development of the larva varies with tem-

perature (Figure 4). The mean duration of the larval stage

was 15.7 days at 23-240 C. and 11.5 days at 28.5-29.50 C.

These means are significantly different at the 1 per cent level.
















I I I I I I I


B I I. I


i F i i it


Ij P s


Figure 3. Feeding rhythms of fifth instars. Black
represents resting and walking, white feeding, and
g girdling. Each division at the top is 15 minutes.


; 1 i i J


i IB -1 1


---. ,1, ....- .. --~I-. ;~-.-


I ]




16



50





25-
i ; .+,

.: ..r -



-' -



2ND 2ND
25 -










i 3 RD 3 RD
25





0
i.
o tr .






T4TH
-" 0 -'-- .---















,
5TH 5TH
25-





0 5.5 0 5.5
DURATION (DAYS)

Figure 4. Duration of the various instars at
23-24 C. (left) and at 28.5-29.50 C. (right).




17

The molting and pupation behavior of A. v. vanilla

was described in detail by Alexander (1961b). This probably

does not differ in most respects from that of A. v. nigrior.

However, Alexander reported that A. v. vanilla almost in-

variably pupates on the stem, tendrils, flowers, or leaves

of its food plant. A. v. nigrior usually pupates on objects

at some distance from the food plant.


The Pupa


The pupa is illustrated in Figures 5 and 6.

Histograms of the duration of this stage are presented

in Figures 7 and 8. The mean duration was 11.7 days at 23-

240 C. and 7.5 days at 28.5-29.50 C. These means are signifi-

cantly different at the 1 per cent level.


The Adult


Emergence

Apparently most emergence from the chrysalid occurs

during the morning. Butterflies which were reared from larvae

in a greenhouse during September under the natural day-night

cycle emerged between 0600 and 1200 with maximum emergence oc-

curring between 0900 and 1000 (Figure 9). On the days during

which emergence occurred, morning civil twilight began at ap-

proximately 0550 and sunrise was at approximately 0610. Alexan-

der (1961b) noted a similar time of emergence for the heliconiine

butterflies Heliconius erato (L.) and H. melpomene in Trinidad.

Upon emergence, the butterfly hangs from the pupal skin




























































Figure 5. Dorsal view of pupa of Agraulis vanilla
nigrior Michener.



























































Figure 6. Lateral view of pupa of Agraulis vanilla
nigrior Michener.








frequency
SO,


days
S5. 0.5 5.5


Figure 7. Duration of pupa at 23-240 C.


. frequency
5 0


I J . - -I- day
0 5 0.5 5.5


Figure 8. Duration of pupa at 28.5-29.50 C.





















frequency
60





















30


Figure 9. Time of emergence of the adult.


t ;me(E ST)




22

until the wings have expanded and dried (Figure 10). Expansion

of the wings requires from 3-4 minutes, and they are dry enough

for flight within an hour.

Sex ratio

Of 265 butterflies which emerged in captivity 54 per

cent were males and 46 per cent females. This sex ratio is

not significantly different from 1:1 at the 5 per cent level.

Reproductive development of the female

Dissections of preserved females indicated that most

individuals reach reproductive maturity 12-18 hours after

emergence, although a few individuals are still not mature 48

hours after emergence. Mature eggs could be recognized in the

preserved specimens by their morphology. In these eggs, there

was a central dark yellow mass occupying no more than 3/4 the

volume of the egg, and the transparent chorion was very con-

spicuous. In the immature eggs, the entire volume of the egg

was occupied by cream colored or pale yellow material, and the

chorion, when it was present, was not so conspicuous. Length

proved to be an unreliable criterion for determining egg

maturity. Oviposited eggs which subsequently produced larvae

ranged in length from 1.30-1.60 mm. All the mature eggs fell

within this size range. However, in several cases immature

eggs 1.30 mm. long were found.

Mating behavior

Females will mate within 24 hours after emergence and

will mate at least as long as 3 days after emergence as pointed

out in the-discussion of methods and materials. Males will






























































Figure 10. Recently emerged adult of Agraulis
vanilla nigrior Michener hanging from the pupal
skin.





24

mate at least as early as 1 day after emergence and as late as

3 days after emergence. No experiments were conducted to de-

termine the two extremes of age at which each sex will mate.

No courtship was observed in the field, and that ob-

served in cages was probably greatly abbreviated. The confined

butterflies alternately rested on the sides of the cage and

fluttered against the sides and top of the cage. When a

fluttering male approached a resting female, the female usually

responded by elevating the abdomen and vibrating the wings with

the hind wings opened 90 degrees and the fore wings opened about

45 degrees. Then the male would land beside the female facing

the same direction, vibrate his wings, and thrust at the female's

abdomen with the end ,of his abdomen. During this process, the

female would continue to vibrate her wings in the described

position. When the ends of the abdomens came in contact, the

male would grasp the end of the female's abdomen with his claspers

and then turn 180 degrees to assume the copulatory position.

Occasionally mating occurred even when the female showed no

response to the male. When both the male and the female were

fluttering, the female would land on the side of the cage, and

the process would proceed as described. Copulation lasted from

45-60 minutes. A detailed study of the mating behavior including

the roles played by motion, color, size, shape, pattern, and odor

remains to be done. Crane (1955) has made such a study of the

related butterfly Heliconius erato, and many of her conclusions

will probably be found to apply equally well to Agraulis vanilla.








Longevity of the adults

Nine males and nine females kept in a constant tem-

perature cabinet at 23-24o C. lived from 14-27 days after

emergence. The mean life span was 18.4 days with a standard

deviation of 3.0 days. There was no significant difference

between the mean longevity of the males and females at the

10 per cent level. Since these butterflies were unmated and

were not subjected to the same stresses normally encountered

in nature, the observed life span is perhaps slightly longer

than that of the species in nature.














DISTRIBUTION OF LARVAL FOOD PLANTS


Presumably any species of Passiflora can serve as a

food plant for Agraulis vanilla nigrior, but only P. incarnata

was examined for eggs and larvae. Only two species of Passi-

flora are widely distributed in the United States (Killip, 1938).

Passiflora incarnata ranges from Virginia to Missouri and south

to Florida and Texas but has been introduced farther north.

Passiflora lutea L. ranges from Pennsylvania to Illinois and

Kansas and southward to Florida and Texas.

Seven species of Passiflora have been recorded from

Florida (Killip, 1938), but no detailed account of their distri-

bution within the state has been published. A general idea of

their distribution was obtained from specimens in the herbarium

of the University of Florida Agricultural Experiment Station.

Apparently P. sexflora Juss., P. pallens Poepp. ex Mast., P.

multiflora L., and P. foetida L. are restricted to the extreme

southern portion of the state. Passiflora lutea occurs in

northern penninsular Florida and in West Florida. Passiflora

suberosa L. ranges throughout peninsular Florida. Passiflora

incarnata occurs throughout the state but is apparently less

common in the south and west. With the exception of P. incar-

nata, which occurs largely in old fields and along roadsides,

these plants appear to occur largely in wooded areas.













POPULATIONS OF Agraulis vanilla IN THE VICINITY
OF GAINESVILLE, FLORIDA


Description of Observed Breeding Areas


Adult gulf fritillaries can be found in almost any open

situation. However, at least in north central Florida, their

reproduction is limited to rather small widely scattered areas

by the patchy nature of the food plant distribution. Four such

areas in the vicinity of Gainesville, Florida, with growths of

Passiflora incarnata were selected for observation (Figure 11).

Area 1 measured approximately 120 x 220 feet and lay in an old

field with growths of broomsedge (Andropogon glomeratus /Walt./

BSP) and Blackberry (Rubus sp.). Late in the summer the food

plants were almost hidden by a dense growth of ragweed (Ambro-

sia artemisiifolia L.). Area 2 measured approximately 50 x 70

feet and was also in an old field with growths of broomsedge

and blackberry, but ragweed was absent. Area 3 measured approxi-

mately 90 x 200 feet. The dominant plants were broomsedge,

blackberry, groundsel-tree (Baccharis halimifolia L.), elder

(Sambucus canadensis L.), and shining sumac (Rhus copallinum

L.). The growth of Passiflora in this area was extremely dense.

Area 4 measured approximately 90 x 140 feet and lay in a pine

flatwoods. Longleaf pine (Pinus palustris Mill.) was the domi-

nant plant. There were widely scattered shrubs including














US 441 FIo 24





X4



A ir-p rt
GAINED SV I LLE



X3















Fl Ia 24 N
Poyne'i s
y^ \a 21Prairie I


US 441






Figure 11. Breeding areas in the vicinity of
Gainesville, Florida




29

waxmyrtle (Myrica cerifera L.), live oak (Quercus virginiana

Mill.), water oak (Quercus nigra L.), Daubentonia punicea (Cav.)

DC, groundsel-tree, and shining sumac. Blackberry was a dominant

plant of the ground cover.


Fluctuations in the Observed Populations


It was not possible to obtain an estimate of the actual

number of eggs and larvae present in a given breeding area at a

given time. However, it was possible to obtain an index of this

number and thereby observe fluctuations. This was done by arbi-

trarily choosing 75 plants in such a way that all portions of

the breeding area were represented and counting the number of

eggs and larvae on the terminals and first six leaves. Later

in the season, when the plant population began to decline, it

was sometimes not possible to find 75 plants. In this case,

as many plants as could be found were examined.

The number of plants examined and the number of eggs

and larvae found at various times between July, 1964, and May,

1965, are presented for each of the four observed breeding areas

in Tables 1-4. In all cases except Area 4, the number of eggs

and larvae increased slightly during July and then remained

fairly constant until the end of August when there was a rapid

increase. Area 4 was apparently unoccupied until the latter

part of August when large numbers of eggs and larvae appeared

there. In all cases this rapid increase in numbers caused a

marked reduction in the available food. The available food was

reduced further in Area 1 by large numbers of blister beetles
















TABLE 1

OBSERVED NUMBER OF EGGS AND LARVAE IN AREA


1 (1964-65)


Larval Instar Eggs
Date Plants Eggs and
1 2 3 4 5 Larvae


Jul

Jul

Jul

Aug

Aug

Aug

Sep

Sep

Oct

Nov

Dec

Dec

Mar

Apr

Apr


2

20

13

31

17

98

100

86

51

16

2

0

0

0

0


2May 75 0 0 0 2 1 2 5


1 2 5


2 May 75 0


0 0 2
















OBSERVED NUMBER OF


TABLE 2

EGGS AND LARVAE IN AREA 2 (1964-65).


Larval Instar Eggs
Date Plants Eggs and
1 2 3 4 5 Larvae


8 Jul 75 0 0 0 0 1 0 1

16 Jul 75 0 0 0 0 0 2 2

22 Jul 75 1 0 2 3 3 3 12

4 Aug 75 5 2 6 3 7 10 33

12 Aug 75 5 0 0 1 3 9 18

19 Aug 75 17 1 0 2 3 1 24

26 Aug 75 33 8 2 0 2 1 46

6 Sep 75 36 13 7 0 4 15 75

24 Sep 25 13 16 12 6 1 9 57

7 Oct 5 3 2 1 0 2 1 9

2 Nov 13 3 1 2 0 2 0 8

18 Nov 10 10 29 5 3 3 5 55

2 Dec 13 0 2 2 4 8 0 16

20 Dec 4 0 0 0 0 0 0 0

14 Mar 0 0 0 0 0 0 0 0

3 Apr 24 0 0 0 0 0 0 0

24 Apr 75 0 0 0 0 0 1 1















TABLE 3

OBSERVED NUMBER OF EGGS AND LARVAE IN AREA 3 (1964-65)


Larval Instar Eggs
Date Plants Eggs and
1 2 3 4 5 Larvae


18 Jul

26 Jul

4 Aug

11 Aug

18 Aug

30 Aug

20 Sep

7 Oct

20 Oct

2 Nov

19 Nov

7 Dec

28 Dec

16 Jan

4 Feb

14 Mar

3 Apr


24Apr 75 1 0 0 0 0 2 3


0 2 3


24 Apr 75 1


0 0 0














TABLE 4

OBSERVED NUMBER OF EGGS AND LARVAE IN AREA 4 (1964-65)


Larval Instar Eggs
Date Plants Eggs and
1 2 3 4 5 Larvae


3 Jul 75 0 0 0 0 0 0 0

18 Jul 75 0 0 0 0 0 0 0

27 Jul 75 0 0 0 0 0 0 0

6 Aug 75 0 0 0 0 0 0 0

24 Aug 75 32 1 1 1 1 3 39

2 Sep 75 7 7 8 15 16 14 67

24 Sep 0 0 0 0 0 0 0 0

14 Mar 4 0 0 0 0 0 0 0

3 Apr 75 0 0 0 0 0 0 0

2 May 75 0 0 1 3 0 0 4




34

(Meloidae) which seemed to be particularly attracted to Passi-

flora. In Area 3, where the growth of Passiflora was very dense,

the food supply remained abundant in spite of the reduction, and

the destroyed plants were soon replaced by new growth. In the

other areas there was only a small amount of new growth, and it

soon became impossible to find 75 plants. The reduction in food

plants was especially marked in Area 4 where it was impossible

to find any plants 31 days after eggs and larvae were first dis-

covered there. The insect was therefore absent from this site

until the following spring. In the other localities, the number

of eggs and larvae began declining in October. Area 2 showed

a second peak in mid-November and then declined again. On Decem-

ber 1, a minimum temperature of 300 F. was recorded at Gaines-

ville Municipal Airport (U.S. Weather Bureau, 1964). This tem-

perature was taken in an instrument shelter 5 feet above the

ground, and it is reasonable to expect that the temperature in

the open near the ground was slightly lower due to the loss of

heat by radiation. The terminals and young leaves of exposed

plants in areas 1 and 3 were damaged by this low temperature,

while those growing under shrubs were not. No damage occurred

to the plants in area 2, probably due to the moderating in-

fluence of the nearby water (Figure 11). The larvae were appar-

ently not injured by this frost. No further freezing tempera-

tures occurred until January when minimum temperatures below

320 F. were recorded at the airport on 8 days and below 280 F.

on 3 days (U.S. Weather Bureau, 1965). This was sufficiently

low to kill all the plants. New shoots emerged in March. Ap-

parently the first eggs were deposited early in April.




35

These observations indicate considerable overlapping

of the generations. This is to be expected since the oviposi-

tion period for each female is relatively long, and the time

required for the insect to pass from egg to adult is relatively

short.

There were seldom more than a few adults present in a

breeding area when observations were made regardless of time

of day and size of larval population. Apparently the adults

spend only brief periods in the breeding areas for oviposition


and possibly for mating.














THE FALL MIGRATION


Methods and Materials


Observational setup

Migrations of the gulf fritillary were observed during

October, 1963, and September, October, and November, 1964, in a

large open field near Gainesville, Florida. A circle 50 feet

in diameter was laid out in this field. The circle was marked

by bottles 5 inches high and 1.5 inches in diameter buried up

to their necks at 20 degree intervals around the circumference.

Before each observation period, a stake 4 feet long was in-

serted in each of the bottles. The stakes were labeled with

large black numbers beginning with 1 at north and continuing

clockwise to 18. After each observation period, the stakes

were removed and the bottles capped. The circle is shown set

up for observations in Figure 12. Observations were made from

stations 8 feet outside the circle. There was one station

directly outside each stake, and they were used in random order

with a different station for each day of observations.

Weather observations

Wind speed and direction were measured by means of a

cup anemometer and wind vane connected to remote wind speed and

direction indicators (Nassau Windmaster, Model No. 409, Science

Associates, Princeton, New Jersey, Figures 13-14). The anemom-

36



















































Figure 12. Setup for observing migrations.



















































Figure 13. Wind vane and anemometer used in migration studies.






















































Figure 14. Wind speed and direction dials used in migration
studies.




40

eter and wind vane were mounted at a height of 5 feet on a

tripod placed 25 feet outside the circle and 20 degrees clock-

wise from the observation station (Figure 15). The remote in-

dicators were at the observation position. Wind observations

were made every half hour in 1963 and every 5 minutes in 1964.

Sky cover and weather conditions were recorded every hour un-

less a major change occurred during the course of an hour.

Sky cover was classified according to the fraction of the

celestial dome covered by clouds as follows:

Clear -- less than 1/10

Scattered -- 1/10-5/10

Broken -- 6/10-9/10

Overcast -- more than 9/10

The term thin was applied to any of the above when the sun was

clearly visible through the clouds. Hourly temperatures were

obtained from U.S. Weather Bureau records for Gainesville Mu-

nicipal Airport which is approximately 7 miles from the obser-

vation site. The temperatures were taken in a standard in-

strument shelter at a height of 5 feet and were probably rep-

resentative of air temperatures over the entire Gainesville

area.

Speed and direction of flight

In describing the flight speed and direction of migrat-

ing butterflies, it is convenient to employ the terminology of

aircraft navigation. The following terms are used:

Track -- the migrant's direction relative to the ground.

Ground speed -- the migrant's speed relative to the ground.



























































Figure 15. Wind vane and anemometer mounted on
tripod for observations.




42

Course -- the direction in which the migrant is heading.

Air speed -- the migrant's speed relative to the air.

Wind direction -- the direction from which the wind blows.

Wind speed -- speed of the wind.

The track of each migrant crossing the circle was deter-

mined by recording the numbers of the stakes between which it

entered and left the circle. It was assumed that the points of

entrance and exit were midway between the stakes through which

the migrant passed. A line through the center of the circle

parallel to the line through these two points gives the track

within + 10 degrees. Ground speed was determined by measuring

with a stop watch the time required for a migrant to cross the

circle and noting the points of entrance and exit as described

above. The wind speed and direction read at the time the mi-

grant left the circle were assumed to represent the wind speed

and direction as it was crossing the circle. The ground speed,

g, in miles per hour is given by the expression

sin 0c4
g = 34.1 t

where t is the time in seconds required for the migrant to

cross the circle and co is the angle subtending the chord of

the circle which represents the path of the butterfly through

the circle.

In calculating air speed and course, angles were

measured counter-clockwise from 0 to 180 degrees and clock-

wise from 0 to -180 degrees with respect to the vector rep-

resenting the track, using the tail of the vector as the origin

(Figure 16). The air speed, v, is given in miles per hour by





43








+90




Wind or Course









Gor >)0
-180 I,* 0O Track











Wind or Courie




-90




Figure 16. Convention used in measuring angles
between track and wind direction (e) and between
track and course (0).







the expression

v = g w cos 8,

where w is the wind speed in miles per hour and 9 is the angle

between the wind direction and the track. The true bearing of

the course, c, is given by the expression

c = a 0,

where a is the true bearing of the track, 0 is the angle between

the course and the track, and

w sin 6
sin 0 = -


Density of the migration

The density of the migration is expressed as the number

of migrants per mile per hour crossing a northeast to southwest

line through Gainesville, Florida. This quantity was estimated

by determining the number of migrants crossing the circle in

one hour. Since the point of entrance or exit was inadvertently

missed for some of the butterflies, this estimate was not as

accurate as it might have been. Of those migrants whose track

was determined, 97.8 per cent had track bearings between 100

and 180 degrees. It is apparent from the geometry of the circle

that any migrant crossing the circle and having a track bearing

within this range must cross a northeast to southwest line 66.4

feet long with its midpoint at the center of the circle (assum-

ing that all migrants enter and leave the circle at points mid-

way between two stakes). Since some of the migrants had track

bearings outside this range, the assumption that all migrants

passing through the circle cross this line results in a positive

error in the density estimate. On the other hand, this line




45

extends 8.2 feet beyond the circle on either side. Therefore,

the assumption that only those migrants passing through the

circle cross the line results in a negative error in the density

estimate. Since both of these errors are probably small, and

since one at least partially cancels the other, a fair estimate

of the migration density can be obtained by multiplying the num-

ber of migrants crossing the circle in one hour by 79.5 (the

number of times 66.4 feet is contained in 1 mile).

A better estimate could have been obtained if the

points of entrance and exit had been noted for every butterfly

crossing the circle. Then it would have been possible in mak-

ing the estimate to consider only those migrants which crossed

the northeast to southwest diameter of the circle, and both

types of error would have been eliminated. Furthermore, in

discussing migration density, it would be desirable to separate

those butterflies which are flying southward from those which

are flying northward. This could be done if the track of every

migrant crossing the circle were known.

Reproductive maturity of the females and sex ratio

Migrating gulf fritillaries were captured with a butter-

fly net to determine the sex ratio among them. Some of the

females were preserved as described previously and later dis-

sected to determine their reproductive maturity and if they had

mated.








Description of the Migration


Characteristics of the migratory flight

Migrating gulf fritillaries fly at a height of 3-6

feet over open terrain, and upon encountering an obstacle,

such as a building or a wooded area, they fly up and over it

without changing their direction. In general, the flight is

very persistent, but occasionally they pause briefly to feed

at flowers. The direction of most individuals lies between

110 and 160 degrees (Figure 17) and does not vary with time

of day (Figure 18). While the path of a migrant over the earth

may be influenced by the wind, the migratory direction is not

determined by this factor (Figure 19). Instead, it appears

to be under the control of the insect itself.

The direction of a flying animal relative to the

earth's surface is determined by its motion through the air and

by the motion of the air itself. If the animal maintains a

constant course, fluctuations in the crosswind will cause

fluctuations in its track. To maintain a constant track, it

must alter its course to compensate for these fluctuations or,

in other words, correct for wind drift. The crosswinds ob-

served during this study were too light to determine if migrat-

ing gulf fritillaries make this correction.

The ground speed of a flying animal is a function of

the energy it expends per unit time and of the wind component

along its course. If the animal expends a constant amount of

energy, its ground speed will be less with a head wind than with



















I i 4 i


B.










N



__________- = 10


Figure 17. Tracks of migrants observed during
the fall of 1963 (A) and 1964 (B). The numbers
in the circles represent the total number of
migrants observed in each case.





48











A. B.













17 D. 10












E. F.
15 &









-5



Figure 18. Tracks of migrants observed at various times
of day on September 23, 1964. (A) 0800-0900 EST, (B) 1000-
1100 EST, (C) 1200-1300 EST, (D) 1300-1400 EST, (E) .1400-
1500-EST, (F) 1600-1700 EST. The numbers in the circles
represent the total number of migrants observed in each
case.


































6
















-2





Figure 19. 'Tracks of migrants and mean wind speed and
direction observed between 1300 and 1400 EST on various
days in the fall of 1964. Wind direction is indicated
in each case by the direction of the arrow. Each full
barb in the tail represents 2 miles per hour of wind
speed. The numbers in the circles represent the total
number of migrants observed in each case.





50

a tail wind, while its air speed will be the same in both cases.

To maintain a constant ground speed, it must alter its energy

output to allow for the effect of wind, and since it is a

function of the energy expenditure, the air speed will vary.

Within the range of observed winds, it appears that each

gulf fritillary expends a more or less constant amount of energy,

but this amount varies from individual to individual. The

ground speed of 23 individuals flying in calm air ranged from

6.9-14.6 miles per hour with a mean of 10.4 (Figure 20), while

that of 11 individuals flying against a head wind of 1-5 miles

per hour ranged from 6.7-11.4 with a mean of 8.4 (Figure 21A),

and that of 9 individuals flying with a tail wind of 1-4 miles

per hour ranged from 8.8-15.6 with a mean of 12.1 (Figure 21B).

The means are significantly different at the 5 per cent level.

The air speed of the headwind group ranged from 8.6-14.6 with

a mean of 11.2 (Figure 22A), and that of the tailwind group

ranged from 8.8-13.3 with a mean of 11.0 (Figure 22B). The

means are not significantly different at the 20 per cent level.

It follows that the ground speed will decrease as the head wind

increases until the butterfly must increase its energy output,

land, or be carried backwards. Which of these alternatives

actually occurs was not determined. The head winds did not

reach this magnitude during the course of the present study,

and they seldom do at the flight level of the migrants.

Variations in migration density

The migration densities determined between 1300 and

1400 Eastern Standard Time on various dates during the course

























per cent frequency
60









30'









0 s peed(MPM)
0.55 10.55 20.55




Figure 20. Ground speed of migrants
flying in calm air.













per cen t Irqq u n c y.
60 ,


30








0


.0.5 5


rd (M Pn)


per cent Irequeny
60
1


30


0.55 10.55


,,pee*d(M PH)
20.55


Figure 21. Ground speed of migrants flying against a
head wind of 1-5 miles per. hour (A) and with a tail wind
of 1-4 miles per hour (B).


r
r

I

r










petr cent Itrqu n cy
60






30






0


'0.55


7r1


10.55


ip..d (M PH)
20.55.


per cenl I requeny
60
1


30


0.55


71



I-f


10.55


- peed (M P)
20.55


Figure 22. Air speed of migrants flying against
a head wind of 1-5 miles per hour (A)'and with a
tail wind of 1-4 miles per hour (B).


0


. 7~




54

of the 1964 migration are presented in Table 5. The density

varies considerably from day to day, but in general, the migra-

tion is heavier during the first half of the migratory period.

The greatest density observed would be classified as extremely

thin according to the scheme of Williams (1958). Wind speed

and direction within the limits observed do not seem to affect

the number of migrants flying. It appears that cloud cover

does not influence the migration density unless the sky is

overcast, and then the migration ceases. On four occasions,

observations were begun within 1.5 hours after sunrise (Table

6). On three of these days, the day's migration had not yet

started when observations were begun. The sky condition was

either clear or scattered on all of these days. These data

suggest that the time at which the migrants begin flying could

be determined by either temperature or light intensity. On

September 23, 1964, the sky was clear and the wind was light

and variable all day, and observations were made throughout the

day. The migratory activity ceased quite abruptly at 1715

EST (about 1.25 hours before sunset). Based on the observations

of this day, the migration density does not seem to vary in a

regular manner with time of day (Table 7).

Reproductive maturity of the females and sex ratio

Of 43 migrants captured between September 22 and Novem-

ber 7, 1964, 72 per cent were females and 28 per cent were males.

This sex ratio is significantly different from 1:1 at the 0.5

per cent level. Since there is no reason to believe that fe-

males are more easily captured than males, it appears that while















TABLE 5

DENSITY OF MIGRATION AND WEATHER OBSERVED
1300-1400 EST (1964)


Number Wind
Date Crossing Density Sky Cover
Circle Speed Direction


20 Sep 9 718 Scattered 00-15 360-060

23 Sep 12 954 Clear 00 -------

25 Sep 7 556 Thin Broken 00-07 030-110

29 Sep 3 238 Broken 00-08 100-170

5 Oct O O Overcast 06-19 250-280

7 Oct 1 80 Scattered 05-12 330-060

9 Oct 10 795 Scattered 00-08 360-090

23 Oct 2 159 Clear 03-07 340-110

25 Oct 1 80 Broken 02-09 050-100

7 Nov 3 238 Scattered 00-08 090-190

18 Nov 2 159 Broken 00-06 330-230













TABLE 6

TIME OF BEGINNING OF MIGRATION ON VARIOUS DAYS


Began Observation First Migrant
Sunrise
Date
(EST) Time (EST) Temp. (OF.) Time (EST) Temp. (OF.)



11 Oct 63 0630 0700 53 0930 64-69

16 Oct 63 0632 0800 66 0930 70-73

18 Oct 63 0634 0800 58 0930 65-72

23 Sep 64 0617 0800 67 0815 67-75


TABLE 7

MIGRATION DENSITIES OBSERVED AT VARIOUS TIMES ON
SEPTEMBER 23, 1964


Number
Time (EST) Crossing Density
Circle


0800-1000 11 874

1000-1100 11 874

1200-1300 19 1,510

1300-1400 12 954

1400-1500 16 1,272

1600-1700 11 874





57

the sex ratio is essentially 1:1 in the total population of

Aqraulis vanilla, the females outnumber the males among the

migrants. Six migrant females were preserved and dissected.

Of these, five had spermatophores in the bursa. Mature eggs

were present in the oviducts of three, and in some, the

abdomen was partially empty, suggesting that they had already

oviposited.















ORIENTATION EXPERIMENTS


Introduction


The ability to maintain a constant compass direction

by referring to the sun and compensating for its apparent move-

ment was first demonstrated in bees by von Frisch (1950) and

in birds by Kramer (1950). Since that time, this ability has

been found in many animals including fish (Hasler, Horrall,

Wisby, and Braemer, 1958), amphibians (Ferguson, 1963), reptiles

(Gould, 1957), and arthropods (Birukow, 1956; Papi, 1955; Pardi

and Papi, 1952), and it has been dealt with in a recent sym-

posium on biological clocks (Long Island Biological Association,

1960) and in a more recent symposium on animal orientation

(Autrum, 1963). An animal which is maintaining a constant

course by means of this time-compensated sun compass changes

its angle with respect to the sun at a rate which is equal in

magnitude and opposite in direction to the angular velocity of

the sun. This mechanism requires a clock furnishing the exact

local time and a knowledge of the sun's angular velocity.

The internal or biological clock which furnishes the

local time can be reset, at least in many cases, by subjecting

the animals to a light-dark cycle which is out of phase with

the natural cycle (Birukow, 1960; Braemer, 1960; Hoffmann, 1960;

Pardi and Grassi, 1955; Schmidt-Koenig, 1960), and the amount by

58




59

which the phase of the clock is shifted depends upon the magni-

tude of the phase shift in the light-dark cycle. Animals in

which the phase of the internal clock has been shifted show a

corresponding phase shift in the orientation rhythm. If, for

example, an animal which has been trained under the natural

sun to search for food in a given direction is subjected for

several days to a light-dark cycle in which the light period

begins and ends 6 hours later than in the natural cycle, it

will search for food 90 degrees to the right of the training

direction when tested again under the natural sun. This

phenomenon provides one means of demonstrating a time-compen-

sated sun compass in an orienting animal.

Frequently, animals which are orienting by means of a

time-compensated sun compass will recognize a fixed light

source as the sun and will change their direction during the

course of the day by changing their angle with respect to this

fixed light source (Birukow, 1960; Braemer, 1960; Kramer, 1952).

The rate of change of this angle is such that a constant direc-

tion would be maintained if the artificial sun were moving with

the angular velocity of the natural sun. This phenomenon pro-

vides another means of demonstrating the existence of a time-

compensated sun compass.


Methods and Materials


The field observations suggested that the orientation

mechanism underlying the unidirectional migratory flight of the

gulf fritillary could be a time-compensated sun compass, so





60

two series of experiments were performed to test this hypothesis.

In one series, orientation tests were made in a room which was

completely dark except for the light provided by a 150 watt

flood light serving as an artificial sun. In the other series,

orientation tests were made on the roof of a three story build-

ing when the sun was clearly visible. The butterflies used in

these tests were captured between September 30 and November 7,

1964, at the site used for observations of the migration. They

were taken with an insect net while in flight or while pausing

to feed at flowers.

The butterflies were tested individually in an octa-

gonal cage with screen sides 24 inches wide and 60.5 inches high,

a screen top, and a plywood floor (Figure 23). The top of the

cage was divided into eight sectors by four diameters. The

butterflies were introduced into the cage by placing them under

an opaque container in the center of the floor and then raising

the container to the top by means of a string extending to the

outside. After the container was raised, they usually remained

on the floor for a short time and then flew to one of the sides.

Periods of rest, when the butterflies sat motionless with the

wings held over the back, alternated with periods of activity

consisting of opening and closing the wings while remaining

stationary or while walking, and of flying about and into the

sides of the cage. The ratio of rest to activity varied con-

siderably from individual to individual and from one time to

another in the same individual. Each butterfly was scored by

recording its position by sector every 10 seconds during periods



























































Figure 23. Cage used for orientation tests.





62

of flight for one hour beginning at the time the container

was raised. If an individual was not scored 25 or more times

during the first half hour, it was considered inactive, and

the test was discontinued.

In the artificial sun experiments, the light was directly

opposite the center of one sector. In the outdoor experiments,

the center of one sector was aligned with true north so that each

sector represented 45 degrees centered about one of the points

of an eight point compass. The scores were analyzed using a

modification of the method outlined by Papi and Tongiorgi (1963).

The direction of the mean vector, 9, and its length, r, were

calculated from the distribution of n scores for each individual.

The sectors were numbered clockwise from 0-7 beginning with the

position of the light, or with north. The direction and length

of the mean vector are given by the expressions

7. 3600
7
Sni sin i .600
tan 6 = and
7
Sni cos i 3600
i o 8



Sni sin i 3600\ + ni cos i 360
i o 'O
r = is te n r of s i t i s T
n


where ni is the number of scores in the ith sector. The direc-

tion of the vector is expressed in degrees measured clockwise

from the position of the light, or from north. The length is a

measure of the dispersion of the scores and varies from 1-0

as the dispersion increases. In the present study, individuals





63

showing values of r less than 0.7 were considered to be dis-

oriented.

Artificial sun experiments were performed on two

migrants. The butterflies were confined individually in cubic

screen cages 4 inches on a side and kept in a greenhouse under

the natural light-dark cycle until they were tested. Observa-

tions were made for one hour every other hour between 0800 EST

and 1700 EST in one case and between 0900 EST and 1600 EST in

the other. The light was located 6 feet south of the center

of the cage at a height of 6 feet. Observations were made from

behind the light.

Outdoor experiments were conducted between October 18

and November 17, 1964, at Gainesville, Florida. Observations

were made from four stations about 3 feet outside the cage, one

at each of the four major compass directions, and each station

was used for 15 minutes during each test. The butterflies used

in these experiments were treated in three different ways. Be-

tween tests, the first group was kept under a light-dark cycle

which was the same as the natural cycle at the time of year

the tests were made. For at least 3 days prior to testing and

between tests, the second group was subjected to a light-dark

cycle in which the light period began and ended 6 hours later

than in the natural cycle. The third group was kept under the

in-phase cycle until one or more tests had been made, then sub-

jected to the out-of-phase cycle for at least 3 days and tested

again. When they were not being tested, the butterflies were

confined in cubic screen cages 4 inches on a side. They were

fed once a day as described previously.




64

The desired light-dark cycles were maintained in con-

trolled photoperiod cabinets in which the temperature was

held constant. One of these cabinets is illustrated in Figure

24. It is constructed of inch plywood on a frame of x 3/4

inch wooden strips and is lined, except for the top, with

inch cane-fiber insulation board (Celotex). The dimensions are

26 x 22 x 34 inches on the outside and 24 x 20 x 33-3/4

inches on the inside. Two 24 inch base fluorescent fixtures

are fastened inside the top and connected to a time switch

(Sears, Roebuck and Co., Model number 5870) on the outside.

Lighting is provided by two 20 watt daylight fluorescent bulbs,

and the interior of the cabinet is painted white to obtain

maximum brightness. The cabinet is partitioned by two panes

of double strength glass supported at distances of 111 and

17 inches from the top by frames of x 3/4 inch wooden

strips. Thus the cabinet is divided into a chamber containing

the lights, a dead air space between the panes of glass, and a

chamber for housing the butterflies. The purpose of the dead

air space is to keep to a minimum temperature fluctuations

in the housing chamber caused by the light-dark cycle. Access

to the housing chamber is provided by a 12 inch high door

across the entire front of the cabinet. A strip of inch

plywood 1 inches wide along the top of the door covers the

crack between the door and the front of the cabinet to exclude

light. Both cabinets were placed in a constant temperature

room, and air was circulated through the housing chambers by

means of a blower. Air entered through a 2 inch diameter hose

























































Figure 24. Cutaway view of controlled photoperiod cabinet
used in clock resetting experiments. (A) time switch, (B)
light chamber, (C) dead air space, (D) air inlet, (E) hous-
ing chamber.





66

in the back of each cabinet and left through a 2 inch diameter

hose in the side. Both hoses were curved to exclude light.

The temperature in the cabinets varied from 24-250 C. This

fluctuation was the same as that elsewhere in the constant tem-

perature room and was not associated with the light-dark cycle.


Results


The artificial sun experiments failed to demonstrate

the existence of a time-compensated sun compass. The test

butterflies directed their flight activity toward the light

throughout the day. The overall illumination in the room was

rather low, and it is possible that under these conditions,

the compass orientation is replaced by a simple positive photo-

taxis. Better results might have been obtained by providing

diffuse light in addition to the light provided by the artifi-

cial sun.

The results of the outdoor tests are summarized in

Figures 25-39. In these figures, north is at the top, and the

small circle represents the position of the sun at.the mid-

point of the test period. Each small dot represents a single

score, the solid arrow represents the direction and length of

the mean vector, and the dashed arrow represents the subjective

direction; i.e., the direction the butterfly would be flying if

it were maintaining the observed angle to the sun 6 hours before

the time of testing. In many cases, the butterfly being tested

was inactive, and in nine cases it was active but disoriented.

This was probably the result of the repeated handling to which

the insects were subjected.





67

Nine butterflies were active and oriented in one or more

tests. When an individual was tested before being subjected to

the phase-shifted cycle, it usually flew in the migratory direc-

tion whether it was tested in the morning or afternoon (Figures

27, 28, 29, 30, 33, 35). In one case, however, the orientation

was reversed (Figures 25-26). This reversal can be accounted

for if the model proposed by Mittelstaedt (1960) for the control

system of time-compensated sun orientation is accepted.

Some individuals which had experienced the phase shift

flew approximately 90 degrees to the right of the migratory

direction (Figures 36, 38, 39), while one flew approximately

90 degrees to the right of the reversed direction (Figures

31-32). If it is assumed that under the experimental condi-

tions, the orientation is sometimes turned 180 degrees, as

appears to be the case, these results provide good evidence

for time-compensated sun orientation.

In the case of Individuals E and G (Figures 34, 37),

the mean vector fell in the northwest quadrant after subjection

to the phase shift. In both cases, however, there appeared to

be a conflict between the reversed migratory direction and the

direction imposed by the phase shift. Individual E flew to the

northeast for the first 45 minutes of the test period and then

to the northwest. Individual G flew to the northeast for the

first 10 minutes and then to the northwest. No explanation for

this directional conflict is immediately apparent.

The results of these experiments suggest that the mi-

gratory direction might be maintained by means of a time-




68

compensated sun compass. While they are too inconsistent to

be conclusive, they are suggestive enough to warrant further

investigation along these lines.


















































Figure 25. Orientation of Individual A when tested
between 0930 and 1030 EST, November 6, 1964, without
resetting the internal clock. -e = 295. degrees,
r = 0.844.



















































Figure 26. Orientation of Individual A when tested
between 1440 and 1540 EST, November 6, 1964, without
resetting the internal clock. 9 = 296 degrees,
r = 0.902.































































Figure 27. Orientation of Individual B when tested
between 0950 and 1050 EST, October 30, 1964, without
resetting the internal clock. 8 = 163 degrees, r = 0.919.


1






















































Figure 28. Orientation of Individual B when tested
between 1410 and 1510 EST, November 5, 1964, without
resetting the internal clock. e = 167 degrees,
r = 0.716.
























































Figure 29. Orientation of Individual C when tested
between 1240 and 1340 EST, November 5, 1964, without
resetting the internal clock. e = 156 degrees,
r = 0.825.


































S \ .........



Figure 30. Orientation of Individual D when tested
between 1510 and 1610 EST, November 5, 1964, without
resetting the internal clock. 9 = 111 degrees,
r = 0.746.



















































Figure 31. Orientation of Individual D when tested
between 1350 and 1450 EST, November 10, 1964, after
setting the internal clock back 6 hours (5 days in
out-of-phase cycle). 8 = 67 degrees, r = 0.853.







































0


Figure 32. Orientation of Individual D-when tested
between 1310 and 1410 EST, November 11, 1964, after
setting the internal clock back 6 hours (6 days in
out-of-phase cycle). G = 61 degrees, r = 0.801.





















































Figure 33. Orientation of Individual E when tested
between 1030 and 1130 EST, 'November 9, 1964, without
resetting the internal clock. Q = 151 degrees, r = 0.904.







































0


Figure 34. Orientation of Individual E when tested
between 1240 and 1340 EST, November 17, 1964, after
setting the internal clock back 6 hours (8 days in
out-of-phase cycle). 6 = 352 degrees, r = 0.700.




















































Figure 35. Orientation of Individual F when tested
between 0930 and 1030 EST, November 9,. 1964, without
resetting the internal clock. 8 = 138 degrees,
r = 0.730.




















































Figure 36. Orientation of Individual Fwhen tested
between 1430 and 1530 EST, November 16, 1964, after
setting the internal clock back 6 hours (7 days in
out-of-phase cycle). 0 = 218 degrees, r = 0.741.


















































Figure 37. Orientation of Individual G when tested
between 1430 and 1530 EST, October 18, 1964, after
setting the internal clock back 6 hours'(5 days in out-
of-phase cycle). 9 = 331 degrees, r = 0.743.



















































Figure 38. Orientation of Individual H when tested
between 1530 and 1630 EST, October 20,1. 964, after
setting the internal clock back 6 hours (3 days in
out-of-phase cycle). 8 = 258 degrees, r = 0.903.























































Figure 39. Orientation of Individual I when tested
between 1430 and 1530 EST, October 23, 1964, after
setting the internal clock back 6 hours (4 days in
out-of-phase cycle). 6 = 202 degrees, r = 0.807.















DISCUSSION AND CONCLUSIONS


Southwood (1960) presented evidence supporting the

hypothesis that in the course of evolution a low level of

migratory activity has been associated with the colonization

of permanent habitats and a high level closely correlated

with the adoption of temporary ones. The prime evolutionary

advantage of migratory movement is the colonization of new

habitats and of previously vacated ones. The observations

made on the gulf fritillary during the course of this study

lend additional support to his hypothesis.

The habitat of Agraulis vanilla nigrior is temporary

in two respects. First, its relatively small and widely

scattered breeding areas are frequently destroyed by the feeding

of the larvae or by the depredations of other insects. Second,

winter temperatures are too low for its survival over the

greater portion of its range. The gulf fritillary is essen-

tially a tropical insect and probably lacks a cold-hardy

stage which would enable it to overwinter in these colder areas.

At the present time, no precise information is available con-

cerning the cold-hardiness of the various stages or what effect

various conditioning factors might have upon this cold-hardiness.

Turner (1963) claimed that this insect overwintered for three

consecutive winters in west-central Missouri. He based this




85

cla:. on the fact that the species was quite abundant on

P. --ifora in this vicinity during three successive summers.

This idea was challenged by Howe (1965) who pointed out that

fr-rles which have traveled from much farther south reach the

latitude of Missouri and Kansas during June and July. He

also reported that 37 chrysalides kept outdoors in a screen

cage during late October in Kansas were all destroyed during

a single freezing night.

The observations made during the course of the research

reported here suggest that the species is not able to pass the

winter even in the vicinity of Gainesville, Florida. If the

insect successfully overwintered in this locality, it would

probably appear in substantial numbers with the return of

favorable conditions. Conditions appear to be favorable for

its development by the first of April, but at this time of

year it is very scarce and remains so until midsummer. This

suggests that the breeding areas in this part of the state are

repopulated by females arriving from farther south.

The coastal areas of southern Florida appear to be

suitable for the development of the gulf fritillary throughout

the year. These localities are less subject to frost than the

inland areas due to the moderating influence of water. During

the 20 years between 1937 and 1957, less than 25 hours of tem-

peratures less than 320 F. were recorded for an area 0-15 miles

wide running along the coast from Palm Beach County to Lee

County (Federal-State Frost Warning Service, 1958). Further-

more, field observations showed that both the larvae and the




86

food plants can survive brief exposures to freezing tempera-

tures. It therefore appears very likely that the gulf frit-

illary continues to breed throughout the winter in these

localities and possibly in other warm areas along the Gulf

Coast.

At least some individuals leave these breeding sites

in the spring and move northward. Apparently the insect is

able to maintain only a low population density during the

winter, as the northward migration is much sparser than the

southward one and is too thin for making measurements of direc-

tion and density by means of the technique described earlier.

The migrating females apparently lay eggs enroute as patches

of the food plant are encountered but do not deposit more than

a few eggs in any one locality before continuing their migra-

tory flight. This movement could account for the first

appearance of eggs and larvae in the vicinity of Gainesville,

Florida, about the first of April and for the appearance of

the insect as far north as Kansas and Missouri in June or July.

Since the breeding areas are widely scattered, only a few of

the females passing through a given latitude will encounter

suitable oviposition sites there. Furthermore, since the

butterflies are widely separated in time and space, we would

not expect all the available breeding sites in a given area

to be occupied at the same time. The observations made in the

vicinity of Gainesville show that this is the case.

It appears that this migration continues until late

summer with the individuals produced in a given locality




87

leaving that locality and moving northward as did their female

(a,in ,erhapb male) parents. This seems to be the only possible

ex:planation for the low population density which prevailed at

Ga:n-.sville through most of the summer in spite of abundant

foo( a ._ favorable weather. No evidence was found which sug-

co.sts that predators, parasites, or disease played a significant

role in preventing a population buildup.

At least in some years, the insect reaches the latitude

of New York. How far each individual travels before it ceases

its migratory flight and leaves the northward expansion of the

range to its offspring is a question which can be answered only

by a tagging program such as was carried out on the monarch

(Urcuhart, 1960).

Late in the summer, some of the butterflies begin moving

southward. This reversal of migratory direction perhaps appears

first in the northernmost segment of the population and spreads

southward as the season advances. This movement results in the

abandonment of the greater portion of the range. The observa-

tions made at Gainesville suggest that not all individuals take

part in this migration, but it is unlikely that the descendents

of those remaining behind survive the winter. The fact that at

least some (and probably many) of the migrant females have mated,

have mature eggs in their ovaries, and have partially empty ab-

domens, strongly suggests that they oviposit enroute. The sud-

den increase in the size of the egg and larval populations in the

vicinity of Gainesville late in th-. summer could be accounted for

by the passage through the area of large numbers of ovipositing




88

females produced in the large northern portion of the range.

The estimates of migration density indicate that the southward

migration was already at or beyond its peak on September 20,

1964, when the first observation was made. This could also

account for the sudden occupancy in August of Area 4 by large

numbers of eggs and larvae after it had remained empty during

most of the summer. The fact that few adults were ever present

in the breeding areas at any one time lends further support to

the hypothesis that the eggs were deposited by migrant females.

The decline of the populations at most of the breeding sites

could be explained by the destruction of food plants, but it

cannot be explained in this manner for Area 3. The decrease in

all the populations (except in Area 4) is probably related in

part to a decrease in the migration density.

The individuals produced from many of the eggs deposited

enroute probably reach maturity and move southward themselves

before the occurrence of freezing temperatures. Again, the

distance traveled by each individual remains to be determined

by a tagging program.

The flight direction of the fall migrants passing through

Gainesville, Florida, is predominately southeastward. This di-

rection may be affected somewhat by the wind but is not deter-

mined by the wind. From the observations presented here, it

must be concluded that the direction of the displacement of the

population is largely under the control of the insects them-

selves. If we suppose, as is probably the case, that the flight

continues in this direction, the migrants will eventually reach




89
t'"e coastal areas of southern Florida. The fact that A. v.

r i r' does not intorcrade with the Bahaman and Antillian

zu: s-.cies A. v. insularis strongly suggests that the migration

<' ,. not extend beyond the Florida Keys.

Tle, pattern of migratory activity described here is

hi -hLy adaptive. The northward migration in the spring results

in L:i colonization of new habitats and prevents extensive

population buildups in the rather small breeding areas which

would result in food shortage and an increase in the rate of

parasitism and disease. The northward direction has a dis-

tinct evolutionary advantage in that the insects are more likely

to find unoccupied oviposition sites in that direction. The

descendents of those individuals which migrate southward in

the fall survive the winter and repopulate the northern breeding

areas the following summer. The descendents of those which do

not migrate perish.

Several important problems concerning the migratory

behavior of the gulf fritillary remain to be solved. The

orientation experiments described here indicate that a time-

compensated sun compass may be the mechanism underlying the

oriented flight, but the results were too inconsistent to prove

this definitely. The best approach to this problem is probably

the performance of artificial sun experiments in which diffuse

ligc:tin, is provided in addition to the light provided by the

artificial sun. Experimental work is needed to determine what

initiates the spring and fall migrations and how the migratory

direction is determined. The most likely initiating factor




90

appears to be either temperature or photoperiod or a combination

o- the two, but this remains to be proved. Both migratory di-

rections may be genetically determined, one being manifested

un:dor one set of conditions and the other under another set

of conditions, or the direction may be determined in another

manner as it is in the great southern white (Nielsen, 1961).

Answers to all of these questions must await future research.













SUMMARY


The larvae of Agraulis vanilla nigrior Michener feed

upon Passiflora incarnata L. and probably other plants of the

ccnus, and the adults oviposit upon and in the vicinity of

thise plants. The insect develops very rapidly, reaching the

adult stage in approximately 28 days at 23-24o C. and in

approximately 22 days at 28.5-29.50 C. Most adults emerge

from the chrysalides during the morning. The females usually

reach reproductive maturity 12-18 hours after emergence, and

the average adult life span is about 18 days under laboratory

conditions.

The adults can be found in almost any open situation,

but because of the patchy nature of the food plant distribution,

the insect can breed only in small widely scattered areas. The

food plants in these small areas are frequently destroyed by

the larvae or by the depredations of other insects. Winter

temperatures are too low for its survival over the greater

portion of its range, but it is probably able to breed through-

out the winter in the coastal areas of southern Florida and in

other warm areas along the Gulf Coast.

The insect has evolved a migratory habit which has

adapted it for the utilization of habitats which are frequently

rendered unsuitable for its survival by the depletion of the

food suply or by low temperatures. Observations of the fall

91




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