Diel and seasonal activities of Culicoides spp. near Yankeetown, Florida


Material Information

Diel and seasonal activities of Culicoides spp. near Yankeetown, Florida
Culicoides spp. near Yankeetown, Florida, Diel and seasonal activities
Physical Description:
xii, 145 leaves : ill. ; 28 cm.
Lillie, Thomas Henry, 1954-
Publication Date:


Subjects / Keywords:
Ceratopogonidae   ( lcsh )
Insects -- Effect of light on   ( lcsh )
bibliography   ( marcgt )
theses   ( marcgt )
non-fiction   ( marcgt )


Thesis (Ph. D.)--University of Florida, 1985.
Includes bibliographical references (leaves 122-143).
Statement of Responsibility:
by Thomas Henry Lillie.
General Note:
General Note:

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Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 000504186
notis - ACS4267
oclc - 22914187
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Full Text







Dedicated to
Michelle, Carrie, and Carla


I am most grateful to the USAF for providing me with such an

incomparable education opportunity through their civilian institutions

program. I am also grateful to Dr. D.L. Shankland and the staff of the

Department of Entomology and Nematology, University of Florida, and the

personnel of the Insects Affecting Man and Animals Research Laboratory,

USDA, Gainesville, Florida, for providing moral and material support for

my research. The resources, time, and suggestions provided by these

organizations are greatly appreciated.

I wish to express sincere gratitude to the members of my committee:

Dr. E.C. Greiner, Associate Professor of Parasitology, for his critique

of the research proposal and review of the dissertation; Dr. D.L. Kline,

USDA, ARS, for his encouragement throughout the research project and for

reviewing the dissertation; and a special note of thanks to my advisor,

Dr. D.W. Hall, Department of Entomology and Nematology, for his guidance

and encouragement, particularly during the qualifying exam. Dr. C.S.

Barfield is acknowledged for his participation in the qualifying exam.

I thank A. Wilkening, K.F. Baldwin, and N. Pierce, USDA, ARS, for

their technical assistance. The residents of Granny's Footprint Island

and Allen's Hickory Island are also acknowledged for their friendship

during the field project.

I owe my utmost gratitude to my wife, Michelle, and daughters,

Carrie and Carla, who served as cheering section throughout my doctoral

program. Their understanding, encouragement, and love made the entire

curriculum more enjoyable.

Finally, I would like to thank the persons who assisted me in my

endeavors to attend graduate school: C.E. Thalken, Lieutenant Colonel,

USAF; Dr. M.E. Dakin, University of Southwestern Louisiana; Dr. D.W.

Fronk, Colorado State University; and my advisor for my M.S. degree, Dr.

W.C. Marquardt, Colorado State University.





LIST OF FIGURES . . . viii




Introduction . .
Literature Review . .
Classification . .
Biology and Bionomics of the Immature
Adult Emergence . .
Mating Behavior . .
Adult Feeding Habits .
The Ovarian Cycle . .
Diel and Seasonal Flight Activity .
Dispersal and Flight Range .
Economic and Medical Importance .
Surveillance and Collection of Adults

Stages .. .
. .

Studies of Ceratopogonids Near Yankeetown, Florida. .


Objectives . . .
Research Site . . .
Materials and Methods . . .
Results and Discussion . . .
Relative Abundance . . .
Seasonal Occurrence . . .
Diel Periodicity . . .
Lunar Periodicity . . .
Diel and Seasonal Host-Seeking Activity .
Lunar Host-Seeking Periodicity . .
Meteorological Conditions . .






Objectives . . 105
Materials and Methods . . 105
Results and Discussion . . 112


Pest Management Applications . 118
Adaptive Significance . . 119




Table Page

1. Sample collection dates on 1 day of quarter phases
of moon in 1983-84 . . 47

2. Relative frequencies for 4 species of Culicoides
attracted to the arm of a human host. (Each value
is a percentage of 9,563 individuals collected.) 57

3. Relative frequencies for 4 species of Culicoides
collected in a vehicle-mounted trap. (Each value is
a percentage of 291,346 individuals collected.) 58

4. Data used to calculate correction factors . 111

5. Number of specimens recaptured, transformed data, and
mean distance traveled by Culicoides mississippiensis
released on 2 April 1984 . .... 113

6. Number of specimens recaptured, transformed data, and
mean distance traveled by Culicoides mississippiensis
released on 16 April 1984 . . 114


Figure Page

1. Location of research site near Yankeetown, Levy County,
Florida, and research sites used by other workers 3

2. Division of 24 h cycle into 20 periods based upon times
of sunrise (SR), sunset (SS), and nautical twilight (NT);
phases of moon used as sampling dates . 45

3. Vehicle-mounted trap used to collect samples . 49

4. Vehicle-mounted trap route. A. Initial 4 km circuit.
B. Final route driven 2 round trips per collection 51

5. Researcher collecting Culicoides spp. with a hand-
held aspirator . . 53

6. Data collection form used to record all data from
vehicle-mounted trap program . . 55

7. Seasonal incidence of C. mississippiensis adults
collected in a vehicle-mounted trap . 60

8. Seasonal incidence of C. furens adults collected in
a vehicle-mounted trap . . 61

9. Seasonal incidence of C. barbosai adults collected in
a vehicle-mounted trap . . 63

10. Seasonal incidence of C. floridensis females
collected in a vehicle-mounted trap . 64

11. Diel periodicity of C. mississippiensis females
collected in a vehicle-mounted trap during
different seasons . . 66

12. Diel periodicity of C. mississippiensis males
collected in a vehicle-mounted trap during
different seasons . . 67

13. Diel periodicity of C. furens females collected in
a vehicle-mounted trap during different seasons 69


Figure Page

14. Diel periodicity of C. furens males collected in
a vehicle-mounted trap during different seasons 70

15. Diel periodicity of C. barbosai females collected in
a vehicle-mounted trap during different seasons 72

16. Diel periodicity of C. barbosai males collected in
a vehicle-mounted trap during different seasons 73

17. Diel periodicity of C. floridensis females collected
in a vehicle-mounted trap during different seasons 74

18. Diel periodicity of male Culicoides spp. collected in
a vehicle-mounted trap on quarter phases of moon 76

19. Diel periodicity of C. mississippiensis females
collected in a vehicle-mounted trap on quarter phases
of moon in the spring . . 77

20. Diel periodicity of C. mississippiensis females
collected in a vehicle-mounted trap on quarter phases
of moon in the summer . . 78

21. Diel periodicity of C. mississippiensis females
collected in a vehicle-mounted trap on quarter phases
of moon in the fall . . 79

22. Diel periodicity of C. mississippiensis females
collected in a vehicle-mounted trap on quarter phases
of moon in the winter . . 80

23. Diel periodicity of C. furens females collected
in a vehicle-mounted trap on quarter phases of
moon in the spring . . 82

24. Diel periodicity of C. furens females collected
in a vehicle-mounted trap on quarter phases of
moon in the summer . . 83

25. Diel periodicity of C. furens females collected
in a vehicle-mounted trap on quarter phases of
moon in the fall . . 84

26. Diel periodicity of C. barbosai females collected in
a vehicle-mounted trap on quarter phases of moon 85

27. Diel periodicity of CC. floridensis adults collected in
a vehicle-mounted trap on quarter phases of moon 87

28. Diel host-seeking activity of C. mississippiensis
during different seasons . . 88

Figure Page

29. Diel host-seeking activity of C. floridensis during
different seasons . . 90

30. Diel host-seeking activity of C. barbosai during
different seasons . . 92

31. Diel host-seeking activity of C. furens during
different seasons . . 93

32. Diel host-seeking activity of C. mississippiensis
collected on quarter phases of moon . 96

33. Diel host-seeking activity of C. floridensis
collected on quarter phases of moon . 97

34. Diel host-seeking activity of C. barbosai
collected on quarter phases of moon . 98

35. Diel host-seekina activity of C. furens
collected on quarter phases of moon . 99

36. Relationship between ambient temperature and flight
activity of 4 species of Culicoides collected in a
vehicle-mounted trap . . 102

37. Relationship between ambient temperature and
host-seeking activity of 4 species of Culicoides 103

38. Researcher injecting fluorescent dust through brass
screen of CDC trap to mark C. mississippiensis adults 107

39. Trap locations and release point for mark-release-
recapture studies near Yankeetown, Levy County, Florida 109

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



Thomas Henry Lillie

May, 1985

Chairman: D.W. Hall
Major Department: Entomology and Nematology

Seasonal occurrence and diel and lunar periodicities of adult

Culicoides mississippiensis Hoffman, C. furens (Poey), C. barbosai Wirth

and Blanton, and C. floridensis Beck were studied near Yankeetown, Levy

County, Florida. From May 1983 to July 1984, a vehicle-mounted trap was

used to collect 3,360 samples of individuals in flight and an aspirator

was used to collect 1,120 samples of individuals attracted to a human

host. Over 300,000 specimens were sorted and identified from these

collections. Culicoides mississippiensis was the only species active

throughout the year. It was also the most abundant, representing over

65% of the total catch. Culicoides furens and C. barbosai were collected

in spring, summer, and fall while C. floridensis was primarily a summer


Diel and lunar periodicities varied seasonally for most species.

Peaks of activity occurred most frequently during morning and evening


twilight periods. The morning peak was greater of the two for C.

barbosai while C. furens and C. mississippiensis were more abundant

during evening twilight. Female activity persisted throughout the night

on full moon but declined after sunset when the moon was in some other

phase. Male activity gradually declined after evening twilight during

all phases of the moon.

The dispersal of female C. mississippiensis was also examined by

marking approximately 40,000 specimens with fluorescent dust and

releasing them in a saltmarsh habitat. About 1.5% (567) of the marked

individuals were recaptured. They traveled a mean distance of 2.0 km

from the release point. The maximum distance traveled by an individual

was 3.2 km.



Biting midges (Diptera: Ceratopogonidae) have hampered land

development in many coastal areas of the Gulf and South Atlantic states

(Dove et al., 1932). Much of the coast of Florida remains unsuitable for

tourist activities because of the annoyance caused by these small biting

midges. Their biting habits have even had an impact on tourism in the

Bahamas and Caribbean area (Linley and Davies, 1971). The midges are so

annoying that U.S. Marine Corps personnel commonly refer to them as

"flying teeth" (Roberts and Kline, 1980). Other common names include

no-see-ums, punkies, gnats, sand flies, and sandfleas (Blanton and Wirth,

1979). The most widely accepted common name is biting midges which

separates them from the phlebotomine sand flies (Diptera: Psychodidae)

and the non-biting midges (Diptera: Chironomidae) (Freeman, 1973).

The biting midges have been studied most extensively in Florida

because of the severity of the problem. The long coastline, extensive

beaches, and tidal waterways serve as ideal areas for their development.

State laboratories at Vero Beach and Panama City, and the U.S. Department

of Agriculture (USDA), Insects Affecting Man and Animals Laboratory at

Gainesville have been involved in the studies. Information on species

composition, seasonal occurrence, and geographic distribution has been

gathered throughout the state, but most of the ecological studies have

been restricted to the Atlantic Coast. In 1977 the USDA initiated field

studies along the Gulf Coast in Levy County near Yankeetown (Figure 1).

Topics which require further study in the Yankeetown area include the

diel host-seeking activity, seasonal periodicity, diel flight activity,

lunar periodicity, and flight range of biting midges.

Literature Review


The biting midges are small (1-4 mm) nematocerous flies. The group

was initially classified by Meigen in 1803 as the genus Ceratopogon in

the family Chironomidae but in 1917 Malloch gave them family status (Kwan

and Morrison, 1974). The family was occasionally referred to as Heleidae

but the International Commission for Zoological Nomenclature classifies

them in the family Ceratopogonidae (Freeman, 1973). They differ from the

Chironomidae in having complete mouthparts and wings with forked media

(Battle and Turner, 1971; Wirth et al., 1977). When differentiated from

other Diptera, the ceratopogonids have long (usually 15 segmented)

antennae, no ocelli, lack of a median furrow or keel on the scutellum,

well developed mouthparts fitted for piercing and blood sucking, and the

costal wing vein ending before the wing tip (Blanton and Wirth, 1979;

Borror et al., 1976).

Further classification of the Ceratopogonidae has been controversial

because some workers used larval characteristics to separate groups while

others used adult characteristics (Wirth et al., 1974). Wirth (1952a)

attempted to resolve the issue by using previously proposed nomencla-

turally formalized subfamily and tribal names based on priority. The

subfamily classification is currently being used and contains the

following: Leptoconopinae, Forcipomyiinae, Dasyheleinae, and





Location of research site near Yankeetown, Levy
County, Florida, and research sites used by
other workers.

Figure 1.

Ceratopogoninae (formerly Heleinae) (Wirth et al., 1974). The largest

subfamily is the Ceratopogoninae.

The differentiation between species is based on antennae, wing

structure, reproductive organs, and coloration on the wings, body, and

appendages (Blanton and Wirth, 1979). In 1974, there were 3,870

catalogued species of ceratopogonids in the world (Wirth et al., 1974).

The current number probably exceeds 4,000 because contributions are being

made periodically. From 1962 to 1974 the number of species in the genus

Culicoides alone increased from 800 (Arnaud and Wirth, 1964) to 924

(Wirth et al., 1974) and by 1979 over 1,000 had been described (Blanton

and Wirth, 1979). There are 60 genera recognized in the family; the

genus Culicoides contains the most species. When compared with other

genera, the adult Culicoides have small tarsal claws without hairy

empodia, large thoracic humeral pits, macrotrichia on the wings, 2 radial

wing cells of about equal length, and the costa usually extends slightly

past midlength of the wing (Johannsen, 1952).

In North America there are approximately 400 species of

ceratopogonids of which 137 are in the genus Culicoides (Downes, 1978c).

Forty-seven species of Culicoides are represented in the state of Florida

(Blanton and Wirth, 1979). An excellent account of the distribution,

biology, and habits of Culicoides species in Florida was prepared by

Blanton and Wirth (1979).

Biology and Bionomics of the Immature Stages

The ceratopogonids are holometabolous insects that develop in a

variety of habitats. The eggs may be oviposited individually or in a

gelatinous mass, but only on rare occasions have the eggs been recovered

in nature (Kettle, 1977). The duration of the egg stage is usually short

(Williams, 1951), but most reports are based on laboratory investigations

where the temperature and other conditions varied little from a constant

setting. Davis et al. (1983b) showed that the development time of C.

mississippiensis Hoffman eggs was inversely related to temperature. At

100C the eggs hatched in an average time of 20 days while at 30C only 3

days were required. Linley (1965a) studied Leptoconops becquaerti

(Kieffer) and also showed an inverse relationship between temperature and

duration of the egg stage.

Most attempts at colonization have shown that the eggs hatch in 2-4

days (Megahed, 1956; Jones, 1960; Linley, 1965b; Linley, 1968a; Mullens

and Schmidtmann, 1981). Leptoconops spinosifrons (Carter) is an

exception to this generalization; the egg stage lasts 12 days at 30C and

may extend for six months at 95% relative humidity (Kettle, 1977).

Another exception is C. vexans (Staeger); the eggs enter diapause and

hatching is delayed for several months (Jobling, 1953).

The larvae lack spiracles (apneustic) and thus rely on cutaneous

respiration. They are generally small (<10 mm) and occur in habitats

which vary from aquatic to terrestrial (Peterson, 1979). The only

requirements for survival are air, food, and moisture. Forcipomyia spp.

have been collected under bark and on wet or damp wood (Wirth et al.,

1977). Species of the genus Palpomyia inhabit pond algae and feed on

chironomid larvae or larvae of phytophagous ceratopogonids (Chan and

LeRoux, 1967). Other species, primarily in the genus Culicoides, have

been found in rotting cacti (Jones, 1962), human sewage (Wirth and

Bottimer, 1956; Jones, 1959), cocoa pods (Williams, 1964; 1966), dung

(Kettle and Lawson, 1952; Neville, 1968), and on the surface of damp

rocks (Dipeolu and Ogunrinade, 1976). The majority of species are found

in typical aquatic habitats such as shallow streams (Jones, 1965; Grogan

and Wirth, 1979), tree-holes (Wirth and Jones, 1956; Smith and Varnell,

1967), leaf axils (Means, 1973), and saltmarshes (Atchley and Hull,


The larvae usually remain within the upper 30 mm of the substrate in

which they develop and the water is usually shallow (Kettle, 1977).

Culicoides denningi Foote and Pratt, however, has been collected from

river beds in water as deep as 10 m although the majority of the larvae

were found on shore along the margin of the water (Fredeen, 1969).

Barnard and Jones (1980a) conducted a thorough study of the ecology of

immature C. variipennis Coquillett and found that most larvae remain in

the upper 10 mm of mud. Prior to their work, several workers had noted

that the larvae of various species have a horizontal stratification

relative to the shoreline (Jones, 1961a; Hair et al., 1966; Rowley, 1967;

Kardatzke and Rowley, 1971). Barnard and Jones (1980a) demonstrated

quantitatively that such a stratification exists and concluded that the

larvae were most abundant in mud 7 cm below the shoreline of ponds in

Colorado. Isaev (1974) also found a horizontal stratification for larvae

of C. odibilis Austen in the Soviet Union. He demonstrated that the

stratification varied seasonally. The larvae were concentrated slightly

above the shoreline in the spring, moved to the water's edge in the

summer, and migrated underwater in the fall. The rate of migration was

influenced by the temperature of the water.

The shoreline is difficult to use as a reference point when studying

saltmarsh or beach inhabiting species because of the changing tides.

Several workers collected C. melleus (Coquillett) larvae in intertidal

sand in situations where wave action is minimal (Jamnback et al., 1958;

Jamnback and Wall, 1958; Wall and Doane, 1965), but Linley and Adams

(1972) showed that the larvae are virtually confined to the region

between the limits of high and low tides. Linley and Adams (1972) also

noted diel changes in the vertical distribution of C. melleus larvae

between depths of 0 and 5 cm, probably in response to heat and light.

The method used to find and collect larvae depends on the type of

habitat. Usually a portion of the substrate is moved into the laboratory

and the immatures are reared to the adult stage. A shovel or posthole

digger is often used to sample for mud-inhabiting species (Kline et al.,

1981b) but a variable depth sampler was designed specifically for

collecting C. melleus larvae (Linley and Adams, 1972). Once the samples

are obtained, different methods are available for extracting the larvae.

Soil-inhabiting Culicoides spp. have been removed from saltmarsh samples

by using sieve/flotation (Kettle and Lawson, 1952; Wirth, 1952b; Kettle

et al., 1956), sand flotation (Bidlingmayer, 1957; Williams, 1960),

direct flotation (Linley and Adams, 1972), and Berlese funnels (Jamnback

and Wirth, 1963). Kline et al. (1975) compared these methods and found

that sieve/flotation was the best method for obtaining C. hollensis

(Melander and Brues) but sand flotation was the best method when C.

furens (Poey) was required.

An agar technique (Kline et al., 1981b) and an inverted funnel

procedure (Boreham, 1981) were later found to be cleaner, less variable,

and more rapid when compared with sand flotation. The two new methods

have yet to be directly compared. The inverted funnel procedure may be

more advantageous when larvae develop in a substrate other than saltmarsh

soil such as C. variipennis which develop in mud on pond margins. Mud

samples containing C. variipennis larvae are simply diluted in water and

the larvae are aspirated 10-15 at a time into a disposable pipet (Barnard

and Jones, 1980a). The inverted funnel would concentrate the larvae and

simplify the process.

Reports of food requirements during larval development vary greatly.

Most aquatic species with prognathous heads are carnivorous while those

with hypognathous heads are herbivorous (Peterson, 1979). Species in the

genus Palpomyia feed on larvae of aquatic insects including those of

their own species (Grogan and Wirth, 1979). Cannibalism has been

reported for species in the genus Culicoides as well (Becker, 1958);

however, such behavior may be the result of conditions under which the

larvae are maintained (Kettle, 1977). Direct examination of the gut

contents and organisms in the habitat of L. spinosifrons indicates that

individuals feed on microorganisms and decaying organic material

(Laurence and Mathias, 1972). Such a diet was also reported for 3 tree

hole Culicoides (Foote and Pratt, 1954) and larvae of other ceratopogonid

genera (Weerekoon, 1953).

Other reports of larval diet were obtained when developing

laboratory colonization techniques (Jones, 1966). Some workers have used

a mixture of materials such as loam, barley, and water (Jobling, 1953);

yeast, soil, and charcoal (Megahed, 1956); soil, fresh cow manure, and

yeast (Jones, 1957); and leaf mold soaked in distilled water (Hair and

Turner, 1966). Jones et al. (1969) use a mixture of commercial products

as a larval medium for C. variipennis. Kettle et al. (1975) reported

that they observed 12 species of Culicoides feeding on small nematodes in

the laboratory. Linley (1979a) developed a technique for culturing

nematodes and other organisms for use as food for predaceous Culicoides

larvae. Nematodes, usually Panagrellus redivivus (L.), were also fed to

Culicoides larvae by several other workers (Koch and Axtell, 1977; 1978;

Mullens and Schmidtmann, 1981; Linley, 1981a). Linley (1966a, 1968a,

1969) used nematodes and oatmeal, alone and mixed together, to rear C.

furens. He concluded that C. furens larvae are omnivorous (Linley,


Larvae develop to the obtect pupal stage in 4 instars (Barnard and

Jones, 1980a). In some species, pupation does not occur until after the

larvae have overwintered (Jones, 1967a; Rowley, 1967). Larvae tend to

move into less saturated areas, usually at the perimeter of the breeding

site, when ready to pupate. Thus, the greatest concentration of pupae

can be found on the margin of streams or ponds for species such as C.

hieroglyphicus Malloch (Jones, 1961a). Even the larvae of C. denningi, a

river-breeding species, move to the shore to pupate (Fredeen, 1969).

Linley (1966a) recorded detailed observations of pupal formation in C.

furens. Pupation could not occur when the larvae were completely below

water; however, once formed, the pupae were capable of floating (Linley,

1966a). In contrast, C. melleus larvae are able to pupate underwater and

the pupae do not float. The inability to float is not detrimental

because the pupae of C. melleus can survive complete submersion for 4

days (Linley and Adams, 1972).

An unusual feature of C. melleus is that seasonal changes occur in

the sex ratio of the pupae while that of the larvae is 1:1. Linley and

Mook (1978) concluded that the seasonal shift, which is biased towards

predominance of males, was most likely due to differential mortality of

unknown origin in the larval stage. Reports on other species indicate

that the sex ratio deviates little from 1:1 (Kettle, 1955), but Werren

and Charnov (1978) have used computer simulation to show that natural

selection could favor seasonal shifts in the sex ratio.

The immatures are naturally subjected to biological factors that

affect their survival. Wirth (1977) covered most of them in a review of

the pathogens and parasites of biting midges. Mermithid nematodes have

been removed from late instar larvae (Glukhova, 1967; Mullens and Rutz,

1982) and rarely from pupae (Rubstov, 1974). Microsporidia have also

been identified from the larvae of biting midges (Chapman et al., 1968;

Kline et al., 1985). Predation is another source of mortality in the

immature stages. A variety of predatory insects, including other

ceratopogonids, attack the larvae and pupae but few cases have been

published (Chan and LeRoux, 1967; Rieb et al., 1980).

Adult Emergence

The emergence of ceratopogonid adults has been assessed by using

several trap designs (Dove et al., 1932; Williams, 1955; Breeland, 1960;

Corbet, 1965; Davies, 1966; Braverman, 1970). The major characteristics

of all traps are a lower section that covers the pupal habitat and an

upper section for collecting emerged adults. The traps have been used

either to examine an area for the occurrence of ceratopogonids or to

monitor the time and frequency of emergence.

Corbet (1964) defines 4 basic temporal patterns of emergence in

insects: continuous, rhythmic, sporadic, and seasonal. Tropical species

appear to have a continuous pattern but periodic seasonal peaks occur

(Davies and Giglioli, 1977). The seasonal peaks of C. furens were

related to fluctuations in the water level in the breeding sites. This

same species has a more distinct seasonal pattern in a temperate climate.

The frequency of adult emergence was strongly correlated with the amount

of rainfall in coastal North Carolina (Kline and Axtell, 1976). In

Florida, the emergence was greatly reduced during cold periods but

increased during brief warm spells (Linley et al., 1970a). When the diel

emergence of C. furens was examined, the majority of adults (97%) emerged

during daylight hours and no emergence occurred between 1900 and 0300 h

(Linley, 1966a).

In most instances the pattern of emergence is seasonal but strongly

rhythmic in response to the moon or sunlight. Culicoides variipennis has

a bimodal rhythmic emergence pattern. One group of both sexes emerge in

equal numbers about 4 h after sunrise and the other group, which contains

more males, emerge in the hour following sunset (Barnard, 1980a). For L.

becquaerti, 98% of the individuals emerge between 0300 and 1100 h while

no adults emerge from 1900 to 0300 h (Linley, 1968b). Kelson et al.

(1980) showed that the emergence of C. occidentalis Wirth and Jones is

seasonal but during a given season it peaks when the moon is full. Lunar

periodicity has also been noted for C. peliliouensis Tokunaga in mangrove

swamps of the Palau Islands (Tokunaga and Esaki, 1936).

Barnard and Jones (1980a) used data from larval population surveys

and adult emergence studies to determine that C. variipennis is

multivoltine in northeastern Colorado. This species had 7 generations,

of which 1 was the overwintering population, during 12 months of

observation. Additional reports of voltinism are available from

laboratory studies. Under optimum conditions, the ceratopogonids studied

have been multivoltine (Jones, 1966).

Mating Behavior

Mating usually occurs in flight but some species have been shown to

mate in confined spaces where flight is not possible (Downes, 1955;

Jones, 1957; Boorman, 1974; Jones and Schmidtmann, 1980). Three general

mating strategies have been described for ceratopogonids: species that

mate in swarms near the host; species that mate in swarms away from the

host; and species that do not mate in swarms (Glukhova and Dubrovskaya,

1974; Kettle, 1977). Culicoides brevitarsis will form swarms either in

the presence or absence of the host but swarms are larger when the host

is present (Campbell and Kettle, 1979). Culicoides variipennis will mate

without swarming but swarms have been observed away from the host and

described in detail (Downes, 1978a; Zimmerman et al., 1982). The

swarming behavior of C. variipennis is similar to that of C. nubeculosus

Meigen (Downes, 1955). Culicoides melleus is a species that does not

form mating swarms (Linley and Adams, 1972).

In species that swarm, the swarm is formed by males. Females fly

into a swarm and a mated pair exit in copula. The ratio of females to

males may be as low as 1:167 (Zimmerman et al., 1982). A typical swarm

is usually formed over some type of marker (Nielsen and Greve, 1950)

which may be an area of high contrast such as grass clumps surrounded by

barren soil (Zimmerman et al., 1982). The males tend to face into the

wind and oscillate upwind and downwind across the marker (Downes, 1969).

The antennal plumes on the male are held in the erect position (Downes,

1955) to sense the wing beat frequency of the female (Roth, 1948).

However, auditory recognition may not be the only cue for mate selection.

Kremer et al. (1979) have detected a highly volatile material that is

released by female C. nubeculosus to attract males. The pheromone also

stimulates copulation. A mating pheromone has been detected in C.

melleus as well but it is a non-volatile contact pheromone (Linley and

Carlson, 1978). The difference in chemical properties with that in C.

nubeculosus is not surprising because C. melleus does not mate in swarms.

The sexual behavior of C. melleus has been investigated in great

detail. Males outnumber females at emergence (Linley and Hinds, 1974).

Mating occurs on the ground, probably near the breeding site soon after

emergence (Hinds and Linley, 1974). In laboratory studies, wingless

females elicit less male response than dead females even though mating

does not occur in flight (Linley and Carlson, 1983). Apparently,

tarsal/wing contact is a necessary part of the mating process.

Virgin female C. melleus are receptive of the male soon after

emergence but become less so with age or upon a second attempt at mating

(Linley and Adams, 1974). A sexually experienced female will resist

mating by kicking the male. The effect of such kicking is dependent upon

the major grooming spines and combs of the tibia (Linley and Cheng,

1974). Resistance by the female reduces the number of sperm transferred

(Linley and Hinds, 1975a, b). Male sensitivity to the kicking declines

with passage of time since his last successful copulation (Linley and

Mook, 1975). The termination of copulation is described in detail by

Linley (1975a). The female will remove the male by kicking and the

spermatophore will remain attached to either sex, usually the male.

Additional studies of reproduction in C. melleus have investigated

ejaculation, spermatophore formation, and sperm motility. Spermatophore

formation and the passage of sperm through the ejaculatory ducts occurs

in the first 2 min of coitus (Linley and Adams, 1971; Linley, 1981b).

The transfer of spermatozoa and male accessory fluids to the spermathecae

accounts for the remaining 8 min of copulation (Linley, 1981c). The

spermathecae create an incoming current by fluid absorption to accomplish

sperm transfer. This current is essential since sperm motility (Linley,

1979b) contributes little to spermathecal filling in C. melleus or other

lower Diptera (Linley and Simmons, 1981). In some instances, multiple

copulations by a single female take place even though the female resists

such encounters. In such cases, complete mixing of sperm occurs in the

female storage organs before oviposition (Linley, 1975b).

Mating is not required for the production of viable eggs in all

species. Culicoides bermudensis Williams (Williams, 1961) and C.

bambusicola Lutz (Lee, 1968) are able to reproduce parthenogenically.

The former may even be capable of multiplying during the immature stage

(paedogenesis) (Kline and Axtell, 1977).

Adult Feeding Habits

The Ceratopogonidae have a broad range of feeding habits which

probably exceeds the range of any other family of Diptera (Downes, 1971).

The general types of feeding behavior are predaceous, vegetarian, and

ectoparasitic but the diversity is great within each category.

Palpomyia spp. prey on insects as adults including males of their

own species (Downes, 1978b). The female seeks out an insect swarm, flies

into the swarm, and exits with a meal. If the swarm happens to contain

males of her own species then simultaneous mating by the male and feeding

upon him by the female will result. An empty male cuticle remains when

the process is complete.

The vegetarian forms feed on pollen or other flower parts.

Atrichopogon glaber Macfie vists flowers of the rubber tree in Brazil and

may function in its pollination (Wirth, 1956a). Forcipomyia spp. feed on

certain nodules on the petals of the cocoa plant but also play an

important role in pollinating the plant (Leston, 1970). In both cases

the female is involved in the process and the feeding behavior of the

male is not reported.

The most common means of feeding is ectoparasitic. Species in this

category will feed on invertebrates as well as warm- or cold-blooded

vertebrates. Forcipomyia spp. have been observed feeding on

caterpillars, stick insects, dragonflies, and lacewings (Wirth, 1956b).

On insects with large wing veins such as dragonflies, the female biting

midge will pierce a wing vein and suck the body fluid. A group of

Atrichopogon spp. are known to attack blister beetles (Wirth, 1956c).

There is even a group of Culicoides spp. that obtain nourishment by

piercing the abdomens of recently engorged mosquitoes (Wirth and Hubert,

1959). Such behavior could contribute toward the transmission of human,

animal, or insect pathogens from one vector to another.

The genera Culicoides, Leptoconops, Forcipomyia, and Austroconops

contain the only vertebrate feeders in the family Ceratopogonidae. Some

species feed only on cold-blooded vertebrates such as C. testudinalis

which feeds on turtles (Wirth and Hubert, 1962) while others attack only

birds (Bennett, 1960) or mammals (Tempelis and Nelson, 1971). Culicoides

piliferus Root and Hoffman has been observed to feed on both birds and

mammals (Humphreys and Turner, 1973).

The range of hosts that a given species feeds upon is important for

epidemiological reasons. When a specific vector-borne disease is being

studied, susceptible animals may be used as bait to find potential

vectors. Such was the case when C. variipennis was collected from horses

during an epidemic of Venezuelan equine encephalitis in 1971 (Jones et

al., 1972; 1977). Culicoides variipennis was also collected from cattle

and sheep during studies of the epidemiology of bluetongue virus in

Colorado (Jones, 1961b; Jones and Akey, 1977).

In other instances a tethered animal or an animal-baited trap may be

used simply to learn more about the biology of ceratopogonids in an area.

Koch and Axtell (1979a) determined that C. furens and C. hollensis will

feed on a variety of hosts in North Carolina. The frequency of response

of the 2 species to trapped animals was related more to the size of the

animal than to the kind of animal. Tanner and Turner (1974) came to the

same conclusion in Virginia but added that the height of the host above

ground level was also an important factor regulating host preference. A

broader range of hosts was used by Hair and Turner (1968). Fourteen

animal species were used including man. Most ceratopogonids collected

showed no specific host preference but C. hollensis was attracted to man

only. Once again, the attraction of C. furens was more related to the

size of the animal than to the kind of animal.

A more recent study in Virginia concentrated on the attraction of

ceratopogonids to livestock (Zimmerman and Turner, 1983). Cattle and

sheep were used and the most abundant species were C. variipennis, C.

biguttatus (Coquillett), C. stellifer (Coquillett), and C. venustus

Hoffman. Livestock were also used to investigate the host-seeking

activity of species in New York state (Schmidtmann et al., 1980b; 1981).

A uniform group of species was collected from pastured calves at several

different trapping locations. The species were C. obsoletus (Meigen), C.

stellifer, C. venustus, C. variipennis, and C. spinosus. Such results

warrant further study of the interaction of these species as they compete

for the same resource.

More specific studies of the ecology of biting midges have addressed

the location where adults prefer to feed on a host as well as the daily

and seasonal biting habits. Culicoides barbosai prefer to feed on the

arm of a human host during daylight hours but at night they have a

preference for the leg (Kettle and Linley, 1969a). Culicoides furens

were more abundant on the leg regardless of the time of day (Kettle and

Linley, 1969b). The preference for legs occurred even when the host was

sitting on the ground and it was more pronounced at night (Kettle, 1969a,

b). Both species attacked in greatest numbers at dusk and dawn. Less

activity occurred during the night and practically no activity was

observed during the day. Leptoconops becquaerti, which bites only during

the day, also showed a preference for legs when compared with arms

(Kettle and Linley, 1967a, b). All three species had a preference for a

particular human host when 4 individuals were exposed simultaneously.

This phenomenon is probably related to some type of chemical cue that

varies between individuals of the host species.

The diel biting activity has been looked at for other species. In

California, C. variipennis attacks hosts at dusk and dawn while L.

knowltoni Clastrier and Wirth has 2 diurnal peaks (Foulk, 1969). Nathan

(1981) found that C. phlebotomus (Williston) seeks hosts during the day

but the majority of biting occurs during crepuscular periods. In

Wisconsin, C. guttipennis (Coquillett) is most active at dusk and dawn

(Scholl et al., 1979). The general pattern of crepuscular biting

activity does not hold true for all Culicoides spp. Culicoides paraensis

Goeldi is only active during the day in Wisconsin (Scholl et al., 1979)

and C. venustus Hoffman is most abundant during the night in New York

(Schmidtmann et al., 1980a).

The seasonal biting activity of a species has been determined by

using animal-baited traps or human hosts for a duration of one year or

more. Studies of such length are rare for blood-sucking ceratopogonids.

Kettle and Linley (1967b) collected biting L. becquaerti females on a

weekly basis in Jamaica and determined that the species is active

throughout the year. Midge abundance was related to the periods of

greatest rainfall. Culicoides furens and C. barbosai were also active

during the entire year in Jamaica (Kettle, 1972). The biting rate of C.

furens was maximal in September and minimal in March. Culicoides

barbosai was most abundant in March-June. Seasonal changes in the

host-seeking activity of C. barbosai were negatively correlated with mean

sea level. The seasonal distribution for Culicoides spp. in Virginia was

reported after collecting specimens in an animal-baited trap, but the

trap was operated for only 4 months during 1970 (Tanner and Turner,


The biting habits of a species can also be influenced by

meteorological conditions. Temperature thresholds definitely exist but

wind speed and light intensity have the most noticeable effects. The

biting activity of C. furens and C. barbosai practically ceases at 20C

(Kettle, 1969b). The attack rate of L. knowltoni was reduced by winds in

excess of 8 km/h (Foulk, 1969). For C. furens and C. barbosai, a wind

speed of ca. 10 km/h caused complete cessation of biting activity

(Kettle, 1969b). Leptoconops becquaerti was much more tolerant of the

wind while seeking a bloodmeal. It remained active in wind speeds of

10-15 km/h and biting did not cease until the wind velocity was in excess

of 24 km/h (Kettle and Linley, 1967b). Studies of the interaction

between feeding and light intensity were performed on C. guttipennis

which is active during crepuscular and nocturnal periods. The greatest

feeding activity occurred between 0.1 and 9.0 fc (Humphreys and Turner,

1971). These intensities correspond to full moon and dawn/dusk

conditions, respectively.

Other studies regarding adult feeding habits have involved examining

the blood of engorged specimens to determine its source. The small size

of ceratopogonids sometimes hampers the process but current immunological

techniques are quite sensitive. Antigen/antibody interactions are the

basis for the tests. The precipitin test has been the most widely used

method (Braverman et al., 1971; Tempelis and Nelson, 1971; Neville and

Anderson, 1972; Walker and Boreham, 1976). Antiserum to the blood of a

given species is produced in a different species. Highly specific

antiserum can be obtained by using closely related species. The blood

obtained from an engorged fly is then exposed to the antiserum. The

formation of a precipitate (i.e., antibody/antigen reaction) is a

positive reaction which identifies the source of the bloodmeal (Clark,

1980). A problem with the precipitin test is that only 4-5 tests can be

conducted with a single specimen. The problem can be overcome by using

hemagglutination inhibition or gel diffusion tests (Murray, 1970), but

they require sophisticated laboratory equipment to perform. Boorman et

al. (1977) have found that the latex agglutination test can be used to

compare a single specimen with a variety of antisera and it shows promise

for application in the field. This method involves the production of

antiserum in the manner described above but then the antiserum is bound

to latex beads. Agglutination will occur when the coated latex is

exposed to the proper antibody (Clark, 1980).

The bloodmeal or other protein meal ingested by ectoparasitic and

predaceous species is used to complete egg maturation. Only the females

ingest a protein meal, but both sexes are known to ingest carbohydrate

materials such as nectar or sugar. Adult longevity is greatly increased

if a carbohydrate source is available (Jamnback, 1961; Linley, 1966b).

The material is also essential for sustained flight by males in mating

swarms (Downes, 1969). Soaked raisins or cotton soaked with a sucrose

solution are used to feed individuals in the laboratory (Jones, 1966).

Nectar of flowers, honey dew, extrafloral nectaries, and sap flowing from

plant wounds are possible sources in nature (Downes, 1958).

The Ovarian Cycle

Like other insects, the ovaries of ceratopogonids consist of several

ovarioles in which the oocytes differentiate and mature (Downes, 1971).

More specifically, the ovaries are of the meroistic type. That is, each

developing oocyte is accompanied by a set of nurse cells which nourish it

during the early stages of development (Linley, 1965a).

Oocyte formation begins while the midges are larvae and progresses

to a resting stage. Further development does not occur until the female

of bloodsucking species ingests a bloodmeal. Linley (1965a, 1966b)

determined that sufficient blood is ingested during a single feeding by

L. becquaerti and C. furens for practically all resting oocytes to

mature. In contrast with these species, the small bloodmeal of C.

barbosai will ultimately yield very few eggs or no eggs at all. This

implies that C. barbosai females probably require multiple feedings to

complete a gonotrophic cycle with all ovarioles in complete harmony. The

sequence of events following the bloodmeal is described in detail by

Linley (1965a, 1966b).

The entire process of oocyte development beyond the resting stage

through oviposition is called a gonotrophic cycle. Jones (1967b)

observed during laboratory tests that C. variipennis females ingest a

bloodmeal for every egg batch and may complete as many as 7 gonotrophic

cycles. The number of cycles can also be determined by dissecting and

examining the ovaries (Linley, 1965c). This technique, called

physiological aging, was first developed by using mosquitoes (Beklemishev

et al., 1959; Detinova, 1962). It is based on the fact that after

oviposition a dilatation remains at the end of the ovariole once occupied

by an egg. Each egg produced by an ovariole and oviposited will result

in a dilatation. Thus 2 dilatations will be present if 2 gonotrophic

cycles have been completed. It is not necessary to examine all ovarioles

for the condition because harmonious development occurs in most species

(Linley, 1965a; 1966b).

Linley (1965c) used the dissection technique to show that C. furens

and C. barbosai complete at least 1 gonotrophic cycle while L. becquaerti

completes at least 2. Culicoides melleus and C. hollensis were also

shown to complete only a single gonotrophic cycle (Magnarelli, 1981). It

is highly probable, however, that a second cycle occurs in these species

because the first cycle is completed without a bloodmeal autogenouss)

(Linley, 1983). The fact that they are known to ingest blood would

indicate the start of a second gonotrophic cycle. Mullens and

Schmidtmann (1982) found relics from as many as 3 cycles in C.


Dissection is a very tedious process but it can be avoided if one is

simply interested in separating individuals that have not oviposited

(nulliparous) from individuals that have completed one or more

gonotrophic cycles (parous). Dyce (1969) noted changes in the ventral

abdominal pigmentation that persisted after oviposition. The condition

occurred in anautogenous as well as autogenous species. Akey and Potter

(1979) applied the technique to C. variipennis populations but also

reported changes in the pigmentation of abdominal tergites (Potter and

Akey, 1978). Akey (1981) found that the method can even be used on

pinned specimens. Mullens and Schmidtmann (1982) compared the method of

Dyce (1969) with that of Potter and Akey (1978) and found the former

method to be more reliable for eastern strains of C. variipennis. When

applied to other species, a change in tergal pigmentation was found to

occur only in abdominal segment 2 of C. furens (Linley and Braverman,


As mentioned previously, some species are able to complete a

gonotrophic cycle without ingesting blood. The nutritional requirements

for egg development are provided by material ingested during the larval

stage and stored primarily in the fat body (Downes, 1971). The oocytes

sometimes develop beyond the typical resting stage before adult eclosion

(Linley, 1982). In biting flies in general, autogeny ranges from a

facultative condition such as in many Culicoides spp. (Linley, 1983) to

an obligate condition such as in the northern strain of the mosquito

Wyeomyia smithii (Coquillett) (Bradshaw, 1980). Nutrient reserves in

ceratopogonids are usually sufficient for only 1 egg batch but L. carter

Hoffman is known to complete more than 1 gonotrophic cycle autogenously

(Schmidtmann and Washino, 1982).

All species in the genus Dasyhelea appear to be autogenous for the

first cycle (Downes, 1971). In other ceratopogonids, the expression of

autogeny varies among individuals of the same species. The rate of

autogeny in C. furens ranged from 0 to 91% for collections obtained from

6 breeding sites within a few miles of one another (Linley, 1966b).

Likewise, C. hollensis obtained from North Carolina were autogenous (Koch

and Axtell, 1978) but populations in South Carolina were all anautogenous

(Henry and Adkins, 1973). It is unknown whether differences between

populations are due to genetic or environmental factors.

Linley (1968c) reported that autogeny is associated with

polymorphism for winglength in L. becquaerti. Smaller individuals are

autogenous and larger individuals anautogenous. This relationship is

opposite of that reported for the mosquito Aedes togoi Theobald

(Laurence, 1964). Linley (1968c) concluded that autogeny and winglength

polymorphism are under genetic rather than environmental control.

Environmental factors are more likely to influence certain aspects of

autogeny such as fecundity rather than the complete expression of

autogeny. Seasonal changes occur in the fecundity of autogenous C.

furens near Vero Beach, Florida (Linley et al., 1970b). Individuals

emerging during cooler times of the year are larger and oviposit about

twice as many eggs as individuals emerging during warmer periods.

Fecundity in autogenous species can also be affected by nutritional

factors in the larval habitat. Lang (1978) and Lillie and Nakasone

(1982) showed that the fecundity of Wy. smithii is influenced by the

protein content of the larval diet.

Oviposition occurs about 7-10 days after emergence in autogenous

species but may occur in as little as 1-2 days in species with precocious

autogeny (Linley, 1982). In anautogenous species a period of 3-12 days,

which is inversely related to temperature, is required between completion

of a bloodmeal and oviposition (Linley, 1965a; 1966b). The number of

eggs produced during that time varies between species and within species.

It can be affected by temperature, season, and larval density.

Culicoides melleus females produce more eggs during cooler times of the

year (Linley and Hinds, 1976). A maximum of 150 eggs/female reaches

maturity in February while only 50 eggs/female mature in August. The

number of eggs matured is inversely related to temperature in C.

barbosai, C. furens (Linley, 1966b), and L. becquaerti (Linley, 1965a).

At 250C, C. barbosai produced the fewest eggs (10/female) and L.

becquaerti produced the most eggs (85/female). The number of eggs

matured was also affected by the larval density during the rearing of C.

variipennis (Akey et al., 1978). Larvae reared under crowded conditions

ultimately yielded adults that produced about half as many eggs as

individuals derived from less crowded conditions. The study by Akey et

al. (1978) also demonstrates that fecundity in an anautogenous species

can be affected by larval rearing conditions.

Diel and Seasonal Flight Activity

The major reasons for flight in ceratopogonids and other biting

flies are to find food, a mate and a suitable oviposition site. Diel and

seasonal patterns of ceratopogonid attraction to a host have been

discussed previously in this report. Patterns of flight activity away

from a host have been studied for several species by using light traps or

vehicle-mounted traps. The effectiveness of the 2 methods varies with

respect to species and location. These and other collection methods will

be discussed in a later section.

Light traps are widely used for sampling insect populations.

Various models have been introduced over the years. The New Jersey trap

(Mulhern, 1942) was one of the first designs and it was followed by a

portable unit, the CDC trap (Sudia and Chamberlain, 1962). The traps

have undergone several modifications to make them more attractive to

insects (Service, 1970), better suited for use in remote locations

(Driggers et al., 1980; Kardatzke et al., 1980), and more efficient for

segregating diel collections (Mitchell, 1982). Other traps have been

designed specifically for collecting ceratopogonids (McDonald, 1970;

Lillie et al., 1979). The traps all take advantage of the attraction of

insects to a light source.

Extensive studies of biting midges have been conducted by using

light traps in Louisiana (Khalaf, 1966; 1967), Florida (Beck, 1952;

1958), and other areas along the Gulf of Mexico (Khalaf, 1969). The

distribution and seasonal abundance of approximately 33 species are

reported from these areas. The majority of species are active primarily

from March to July.

Seasonal and diel periodicities have been determined in other areas

by using suction traps that automatically cycle at preset intervals (Koch

et al., 1977) or by manually changing the collection bag on light traps

(Brenner and Wargo, 1984). The traps may be baited with CO2 (dry ice) to

attract host-seeking individuals (Nelson, 1965) and to make the traps

useful during daylight hours. Studies of this nature typically show that

bloodsucking ceratopogonids have a bimodal activity pattern with peaks at

dawn and dusk. Culicoides furens and C. hollensis have this type of

activity but C. furens is active at night as well, and C. hollensis is

most active at sunrise (Koch and Axtell, 1979b). The dawn peak for C.

barbosai is also greater than that observed at dusk (Kline and Roberts,

1982). The activity of L. torrens Townsend, L. foulki Clastrier and

Wirth, and L. knowltoni is diurnally bimodal rather than crepuscular.

Collections of these three species are greatest just before sunset and

just after sunrise (Brenner et al., 1984a; Brenner and Wargo, 1984).

In some cases, changes in the frequency of individuals collected in

light traps have been correlated with changes in meteorological

conditions. Culicoides furens activity is inversely related to wind in

coastal North Carolina (Koch and Axtell, 1979b). Flight is inhibited at

wind speeds >5.0 km/h but a few individuals have been collected during

wind speeds as great as 12.2 km/h. Temperature and activity of C. furens

have not been shown to be correlated in North Carolina (Kline and Axtell,

1976; Koch and Axtell, 1979b) or Grand Cayman (Davies and Giglioli,

1977). The results for C. hollensis are less consistent. Kline and

Axtell (1976) did not find a correlation between temperature and C.

hollensis activity but Koch and Axtell (1979b) did. The traps were not

baited during either study. The difference may be the result of

experimental design. Kline and Axtell (1976) conducted their study over

a 2-year period while Koch and Axtell (1979b) obtained their data between

March and August of a single year. By limiting their study to the active

season for C. hollensis, Koch and Axtell (1979b) had fewer extraneous

factors to influence their results.

In Kenya, the activity of C. pallidipennis C., I. and M. and C.

schultzei (Enderlein) is inhibited by wind in excess of 10 km/h but

stimulated by high temperature and relative humidity (Walker, 1977).

Optimum conditions for activity occurred during the night when the

relative humidity was high and the temperature had not decreased to an

inhibitory level. Temperature as well as rainfall influenced the number

of biting midges collected in light traps in Taiwan. Fewer individuals

were collected during cooler months and seasons of heavy rainfall (Sun,

1963; 1964).

Some researchers have elected to use a vehicle-mounted trap rather

than light traps for assessing patterns of flight activity. A large net

is positioned on the top or side of a vehicle. The vehicle is driven

over a predetermined course and any objects intersecting the trap are

funneled into a receptacle. Changes in the abundance of flying organisms

can be monitored by periodically changing the receptacle. This type of

trap is a more recent addition than light traps to the repertoire of

sampling devices. Early models consisted of a funnel apparatus mounted

on the fender of a vehicle (Chamberlin and Lawson, 1945; Stage, 1947).

Provost (1952, 1957) used the fender model but also experimented with a

unit mounted on top of a truck. Bidlingmayer (1966) preferred the top

mounted model for his studies of mosquitoes. Designs are available that

contain multiple collection bags with a valve system to segregate

periodic collections without changing the collection bag (Sommerman and

Simmet, 1965; Davies and Roberts, 1973); however, these traps are bulky

or difficult to construct. Current models were designed with weight and

portability as major considerations (Loy et al., 1968; Barnard, 1979;

Holbrook and Wuerthele, 1984).

Bidlingmayer conducted several studies of biting midges and

mosquitoes with a vehicle-mounted trap near Vero Beach, Florida (Figure

1). Culicoides furens was active for a brief period after sunset and

preceding sunrise (Bidlingmayer, 1961). Irregular peaks were also noted

during the night but the cause of the nocturnal activity was not

determined. He also showed that the mosquitoes Aedes taeniorhynchus

Wiedemann and Ae. sollicitans (Walker) were most active at dusk and dawn

but their nocturnal activity increased as the intensity of moonlight

increased (Bidlingmayer, 1964). Culicoides variipennis, another

crepuscular species, is also influenced by moonlight. The flight

activity of this species is greater during moonlight hours than in darker

periods of the night in California (Nelson and Bellamy, 1971) and

Colorado (Barnard and Jones, 1980b).

Studies with vehicle-mounted traps have shown that the diel activity

of a given species may change throughout the year, often in response to

temperature and light intensity. Culicoides variipennis activity peaked

earlier in relation to sunset in the spring and fall than in the summer

(Nelson and Bellamy, 1971; Barnard and Jones, 1980b). Culicoides

crepuscularis Malloch, however, remained most active immediately after

sunset regardless of the season. Culicoides spp. flight activity in

general was inhibited at temperatures <70C or >350C in Colorado (Barnard

and Jones, 1980b).

The vehicle-mounted trap is one of few methods of obtaining males in

nature. Males tend to be active for a shorter duration of the diel cycle

than females (Nathan, 1981; Nelson and Bellamy, 1971), possibly because

of the large expense of energy required for sustained flight in mating

swarms. The trap could easily intercept the swarms (Edwards, 1980), and

bias the results, since they are often formed over areas of high contrast

(Nielsen and Greve, 1950) such as bright patches on a dark road or vice

versa. Male activity was shown to increase during periods of moonlight

for C. crepuscularis (Barnard and Jones, 1980b) and C. variipennis

(Nelson and Bellamy, 1971). Bidlingmayer (1961) was not able to collect

a sufficient number of male C. furens to make any conclusions regarding

their activity in Florida.

Studies of the diel and seasonal flight activities of non-biting

ceratopogonids are rare. Barnard (1982) investigated species in the

genera Atrichopogon, Bezzia, Dasyhelea, Forcipomyia, and Palpomyia by

using a vehicle-mounted trap in northeastern Colorado. The diel

periodicity of 8 species he collected during the study varied seasonally.

The flight activity of 3 predatory species, P. tibialis (Meigen), B.

setulosa (Loew) and B. pulverea (Coquillett), coincided with the flight

activity of their prey.

Dispersal and Flight Range

The dispersal and flight range of adult ceratopogonids have been

evaluated by collecting unmarked adults in the vicinity of an isolated

breeding site or by releasing and recapturing marked specimens. Most

studies are based on the former procedure which is much easier to

conduct. The mark and release method is more time consuming because the

adults must be obtained by live trapping or rearing from the immature

stage. They are then marked by using radioisotopes (Davies, 1965),

fluorescent dusts (Lillie et al., 1981a), paints (Gillies, 1961), or dyes

(Dalmat, 1950).

Culicoides variipennis was observed attacking livestock at short

distances from a breeding site in Oklahoma. The distance, which extended

up to 3.2 km from the breeding site, varied according to the direction of

the prevailing wind and the topography of the land (Whitehead, 1935). In

other areas, this species has been observed 1.6 (Dyce, 1969) to 2.0 km

(Jones and Akey, 1977) from breeding sites. Zimmerman and Turner (1984)

placed sticky panels at various distances ranging from 20-900 m from an

isolated breeding site in southwestern Virginia. The number of C.

variipennis captured declined with distance from the breeding area and

most individuals were within a 100 m radius of the site. Mark, release,

and recapture studies have shown that the females of C. variipennis can

travel at least 4.0 km and the males only 800 m over an 8-day period

(Lillie et al., 1981b).

Marking studies have not been conducted with C. furens but it has

been observed to travel considerable distances from isolated breeding

sites. Adults were collected 3.2 km downwind of a breeding site in

Panama (Breeland and Smith, 1962) and over 6 km away from breeding

grounds in the Virgin Islands (Williams, 1962). The wind most likely

played an important role in these instances, particularly in the Virgin

Islands where the adults had to traverse mountains over 360 m high. In

Florida, the females remained within 1.2 km and the males within 90 m of

the site of immature development (Bidlingmayer, 1961).

Another species, C. impunctatus Goetghebuer, was collected in

decreasing numbers as the distance from an isolated breeding site

increased, until the catch dropped to zero at a distance of ca. 275 m

(Hill, 1947). Kettle (1951a) determined in a more extensive study in

Scotland that the average flight range for C. impunctatus was ca. 74 m.

Culicoides grahamii also remained close to their breeding sites as

adults. Nicholas (1953) used biting collections to assess the dispersal

of this species in the Cameroons. The biting rate at 340 m was 90% less

than the rate near the breeding site.

The most recent assessment of the dispersal of a ceratopogonid was

conducted in the desert of southern California (Brenner et al., 1984b).

Culicoides mojave Wirth females traveled a mean distance of 1.94 km

during a 30 h period following their release. The majority of specimens

were recovered in the direction of the prevailing wind but one individual

had dispersed 6.0 km against it.

The number of individuals recaptured during mark and release studies

typically declines rapidly with time postrelease. Kettle (1951b)

attributes the delcine to the dilution effect, behavioral/physiological

changes, the mortality effect, or a combination of these factors. The

dilution effect refers to a decrease in the number of midges/unit area as

the distance from the release point increases. The change in the number

of traps/unit area is also inversely related to the distance from the

release point. Thus, the probability of recapturing marked specimens

declines rapidly and drops to zero when midges travel beyond the

recapture area. Behavioral/physiological changes will occur and the

likelihood of an individual dying increases with time (mortality effect).

Host-seeking individuals are attracted to CO 2-baited traps but the

physiological events that occur after ingesting a bloodmeal will alter

this behavior.

Economic and Medical Importance

Ceratopogonids play a role in the pollination of rubber trees

(Wirth, 1956a) and cocoa plants (Leston, 1970) but they are best known

for their vicious biting habits. Only species in the genera Culicoides,

Leptoconops, Forcipomyia, and Austroconops are known to feed on

vertebrates. The Culicoides are the most important as far as human and

animal health are concerned.

The biting habits of several species have restricted or prevented

human activities in many areas. Land development and tourism in coastal

areas of Florida have suffered because of high populations of Culicoides

spp. and the nuisance they create (Linley and Davies, 1971). Studies

have shown that Culicoides spp. and Leptoconops spp. prefer to bite on

the legs rather than parts of the upper body (Kettle, 1969a, b; Kettle

and Linley, 1967a, b) but their attack is not limited to the lower limbs.

Individuals crawling over the scalp and biting on the upper neck are the

most annoying (Linley and Davies, 1971). The number of bites that a

human can tolerate will vary from person to person and with the type of

activity. Linley and Davies (1971) have estimated that most people will

not tolerate more than 5 bites/h for most outdoor activities. People

demand some type of personal protection when biting is more intense. The

bite produces a red wheal which is often accompanied by itching for 3-5

days (Hinman, 1932). Secondary infection may result. Reaction to the

bites can be more severe in some humans and animals. Allergic dermatitis

of horses caused by Culicoides bites has been reported in Australia

(Riek, 1954).

Biting ceratopogonids have long been considered potential disease

vectors but their small size and difficulty to colonize in the laboratory

have hampered disease transmission studies. Nevertheless, evidence is

gradually being gathered which incriminates several species in the

epidemiology of protozoan, filarial, and viral infections (Blanton and

Wirth, 1979). Kettle (1965) reviewed the literature on those organisms

transmitted to man and animals by ceratopogonids. Linley et al. (1983)

provided a more current review of the organisms transmitted to man.

The protozoans vectored by biting midges do not develop in humans.

Leucocytozoan caulleryi Mathis and Leger is an important pathogenic

parasite of poultry that is transmitted by C. arakawai (Arakawa) in Japan

(Akiba, 1960). Other protozoans associated with Culicoides spp. have

been found in wild birds (Fallis and Bennett, 1960) or monkeys (Garnham

et al., 1961).

The majority of organisms isolated to date from ceratopogonids have

been filarial worms. The species found in man are Mansonella

(Dipetalonema) perstans in Africa and Central and South America (Hawking,

1977; 1979), M. (D.) streptocerca in Africa (Hawking, 1977), and M.

ozzardi in the Caribbean Basin and South America (Hawking, 1979). Each

may produce mild clinical symptoms but, in general, they are considered

non-pathogenic. Ceratopogonids have also been linked with the

transmission of nematodes in horses, cattle, and wild birds. Hibler

(1963) studied filarial worms that develop in the American magpie, Pica

pica hudsonia (Sabine), and found 3 species that are vectored by C.

crepuscularis and C. haematopotus. He showed that the number of

microfilaria circulating in the blood of the magpie fluctuates during the

diel cycle. The peak abundance of microfilaria coincides with the peak

host-seeking activity of the vector. This most likely resulted from a

long term association between the vector and the parasite, both of which

have a short life cycle and a high biotic potential. The activity of the

vector may have served as selection pressure for individuals of the

parasite species that were in the proper stage of development during the

time the midges feed.

Another important category of pathogens transmitted by certopogonids

are the viruses. Oropouche virus is probably the most important type

affecting man directly. It occurs in South America where 5 epidemics

have occurred among humans between 1961 and 1972 (Pinheiro et al., 1976).

The clinical picture includes fever, chills, headache, myalgia,

arthralgia, and dizziness. Illness to the point of prostration has been

reported but no fatalities are known. The vector is C. paraensis. A few

other viruses which affect humans, including encephalitis, are suspected

of being transmitted by ceratopogonids but definitive proof is lacking.

One reason for a lack of proof is that researchers have failed in some

instances to examine the proper species when a given virus is studied

(Blanton and Wirth, 1979). For example, attempts at transmitting eastern

equine encephalitis (EEE) in the laboratory by using C. variipennis were

unsuccessful (Scanlon, 1960). Perhaps C. crepuscularis would have been a

better candidate because it is an ornithophilic species and the EEE virus

normally cycles among bird populations (Blanton and Wirth, 1979).

The evidence is much more substantial for several viruses in wild

and domestic animals. Culicoides variipennis is the vector of

buttonwillow (Hardy, 1970), lokern, and main drain viruses (Nelson and

Scrivani, 1972) among leporids in California. The same species is also

incriminated in the transmission of bluetongue virus, an organism which

affects sheep (Luedke et al., 1964), cattle (Bowne et al., 1967), goats

(Luedke and Anakwenze, 1972), and wild ruminants (Trainer and Jochim,

1969) in several parts of the world including North America. The disease

is most severe in sheep. As much as 70% of the infected animals may die

during an outbreak (Gambles, 1949). In cattle, bluetongue is usually

considered an inapparent infection; cattle can become carriers and as

such may serve as reservoirs of infection (Bowne et al., 1968). The

cattle industry has suffered because the virus can be transmitted by an

infected bull during copulation and the pregnancy often ends in abortion.

Certain countries have placed embargoes on the import of cattle and semen

from bluetongue endemic areas. This has resulted in the loss of several

million dollars (Bowne, 1973).

In some instances, specimens from laboratory colonies have been used

in an attempt to document the potential of biting midges as vectors.

Culicoides variipennis and C. nubeculosus are often used because large

colonies of both species exist. Jones and Foster (1978) recommend that

researchers be cautious when interpreting results from these studies

because an erroneous conclusion can be obtained. The colonization

process selects for individuals most suited to laboratory conditions;

hence, the gene pool of the wild strain is lost during the early phases

of colonization. Theoretically, a new species could evolve in the


Surveillance and Collection of Adults

Ceratopogonids can be collected by using a sweep net, a hand-held

aspirator (biting collections), animal-baited traps, light traps, suction

traps, vehicle-mounted traps, sticky cylinders, emergence traps, or

ground suction devices (D-vac). Each method will give an indication of

the species occurrence and relative abundance but all have some type of

bias. The time of day, phase of the moon, or trap location may have a

drastic effect on the results obtained with a given method.

The sweep net is a reliable collection method but a haphazard

surveillance technique. It is a good device for preliminary studies with

the objective of determining the presence or absence of ceratopogonids.

A quantitative comparison of several areas is difficult because of the

inherent bias of the collector. Consistency is difficult to maintain

over a long period.

A hand-held aspirator can be applied more consistently but its use

is somewhat limited to biting species. Quantitative comparisons can be

made between hosts or trapping locations if the study is properly

standardized to reduce the number of extraneous factors. Results will

vary with the species of host employed (Koch and Axtell, 1979a), the

individuals involved (Kettle and Linley, 1967a), the part of the host

sampled (Kettle, 1969a), and the location of the host (Tanner and Turner,

1974). Animal-baited traps also have many of these biases plus the

collection can be influenced by the design of the trap. Aspirator or

animal-baited trap techniques are best suited for instances where the

host range or diel biting activity are being studied.

Light traps are commonly used for the collection and surveillance of

a variety of insects. Collections from the same location over a long

period of time can provide useful data about the seasonal trends of a

given insect population. The number of specimens collected can be

influenced by the color of the trap (Kohler and Fox, 1951), the color of

the light (Gui et al., 1942), the brightness of the light (Barr et al.,

1963), and the location of the trap (Bidlingmayer, 1967). The addition

of attractants such as CO2 (Nelson, 1965; Reeves, 1951) and animal

extracts (Fallis and Smith, 1964) increases the number of individuals

collected and allows the trap to function as a sampling device during

daylight hours.

Moonlight has been shown to have an effect on light trap

collections. The background light provided by the moon reduces the

degree of contrast created by the light trap. Provost (1959) determined

that this reduces the number of mosquitoes collected when the moon is

full. Other workers have noted the same phenomenon for several types of

insects (Bowden, 1973; 1981; Bowden and Church, 1973) including

ceratopogonids (Kline and Axtell, 1976). The effect of moonlight can

vary with trap location (Bidlingmayer, 1967). Light traps placed in open

areas had a reduced catch during full moon while those in wooded areas

did not.

The effects of moonlight can be eliminated by removing the light

source and operating the trap simply as a suction device but with a

larger fan to increase the volume of air sampled. Results with this

technique contradict the data from light trap collections. Mosquito

activity increased during full moon (Bidlingmayer, 1967). The suction

trap is best suited for studies of the diel and seasonal flight

activities of a species. The collection is not biased towards

host-seeking individuals since no attractant is used.

The vehicle-mounted trap also showed a positive correlation between

moonlight and the number of biting midges collected (Nelson and Bellamy,

1971). This trap, like the suction trap, does not employ an attractant.

It tends to collect more males than light traps and is not influenced by

moonlight (Barnard, 1980b). The results could be misinterpreted,

however, because the trap is operated over open roads where males of some

species form swarms. Nathan (1981) observed swarms of C. phlebotomus

being intercepted by a vehicle-mounted trap. Data from the diel trapping

of this species are actually an account of male swarming times over the

collection route rather than general flight activity of males over other

areas. Thus, detailed observations should be recorded when operating

this and other traps to accurately interpret the results.

Initial costs to construct the vehicle-mounted trap are not high

compared to light traps but the operating cost can be prohibitive since

the vehicle must be driven to use the trap. Vehicle maintenance, fuel,

and pay for the operator must be considered when planning a study. When

used, however, it is an excellent method for monitoring diel and seasonal

changes in the flight activity of species that frequent open areas. The

catch is clean, easy to sort, and the specimens can be used for virus

isolation tests.

The sticky cylinder trap is another means of collecting specimens

without the use of an attractant. A typical trap is composed of plastic

sewer pipe coated with Tanglefoot (Kline and Axtell, 1976). The color

of the trap will affect the results. Black cylinders and red cylinders

collect significantly more specimens than white (Castle, 1965). The trap

is positioned a given height above ground level and any biting midges

that intercept it are retained in the Tanglefoot. Sticky traps are a

reliable method of monitoring seasonal changes in adult ceratopogonid

populations but the cleanup and sorting of specimens is tedious. Kline

and Axtell (1976) found that this technique was more sensitive than light

traps for detecting the beginning and end of the seasonal occurrence of

C. furens and C. hollensis. The sticky trap is also less expensive to

construct and operate than light and suction traps.

Emergence traps are easy to construct and are also more sensitive

than light traps for detecting the commencement and termination of

seasonal occurrence of a species (Kline and Axtell, 1976). Males are

usually collected more frequently with this method than any other method

previously discussed. The sex ratio of the sample is typically 1:1 but

diel (Barnard, 1980a) and seasonal (Linley and Mook, 1978) changes occur

in some species. Emergence traps are best suited for locating breeding

sites and for comparing the productivity of different sites. They do not

require a power source but the size of the area sampled is usually small

and the specimens are often in poor condition (Kline and Axtell, 1976).

Barnard (1980a) noted that the presence of the trap causes the

temperature of the substrate to increase. This could shorten the

development time and bias the results. He provides a systematic method

of randomly moving traps during a study to avoid such a problem.

The ground suction device or D-vacd is used less often than the

other methods for collecting ceratopogonids. It is essentially a

portable suction trap which is ideal for sampling various surfaces in the

environment for the presence of adults. Bidlingmayer (1961) used the

device to study C. furens in Florida. He found that males preferred to

rest in the trees whereas females occurred in about equal numbers in the

trees and on the ground. Males remained closer to the saltmarsh than

females. Tanner and Turner (1975) used it for a study of Culicoides spp.

in Virginia. Their results indicate that the D-vac collected fewer

specimens than light traps or animal-baited traps but the species

diversity was greatest when the D-vac was used. The increased diversity

most likely occurred because the portability of the D-vac allows it to

be used over a broader area and range of habitats than the other 2


It is obvious from this review that the selection of a sampling

device depends upon the objectives of the study for which it will be

used. Each trap is best suited for a particular situation. Bidlingmayer

(1974) compared most of these methods and concluded that the

vehicle-mounted trap and the suction trap are less subject to

environmental and meteorological influences. These two methods can,

therefore, provide a less biased sample of airborne insect population


Studies of Ceratopogonids Near Yankeetown, Florida

The Gulf Coast community of Yankeetown, Levy County, Florida (Figure

1), is one area where land development has been restricted by the biting

midge population. Extensive saltmarshes with black needle rush, Juncus

roemerianus Scheele, and smooth cordgrass, Spartina alterniflora

Loiseleur, make the location ideal for development of immature biting

midges (Kline, 1980). Personnel at the USDA, Insects Affecting Man and

Animals Laboratory have been conducting studies of the pest species in

that area since 1977. Their studies have focused on the biology and

control of 3 major pests: C. mississippiensis, C. furens, and C.

barbosai (Kline, 1984).

Kline et al. (1981a) developed a technique for extracting larvae

from saltmarsh soils and used it to study the ecology of breeding sites.

The distribution of immature stages throughout the saltmarsh is

associated with plant cover (Kline, 1984). Larval population density was

greatest in samples taken from sites where Distichlis was growing but an

extrapolation of the data to account for the total area occupied by each

plant type revealed that the majority of larvae (63.6%) are associated

with Juncus grass. When meteorological conditions were examined along

with plant cover, the larvae best survived periods of flooding in

Distichlis habitats and periods of low water levels in Spartina habitats.

This information is useful for a pest management program and the use of

remote sensing infrared photography equipment to identify plant types

makes it practical.

The diel and seasonal abundance of adults were determined by using

modified New Jersey light traps (Koch et al., 1977) baited with CO2

(Kline, 1984). Culicoides mississippiensis was present throughout the

year and in greater numbers than any other biting midge. It was most

abundant in spring and fall with peaks in late May and late November.

The greatest activity during the diel cycle occurred between 4-7 pm EST

in the fall and 4-11 pm in the spring but sometimes females were active

throughout the day. Culicoides furens and C. barbosai were both active

during May through October, C. barbosai being the least prevalent of the

2 species.

The biology of C. mississippiensis was examined in the laboratory

(Davis, 1981). The optimum temperature for larval development was 200C.

A total of 57 days were required to develop to the adult stage at this

temperature (Davis et al., 1983b). Autogeny was demonstrated for the

first gonotrophic cycle but a bloodmeal is required for subsequent egg

batches. The procedure for giving a bloodmeal was simplified with the

development of a reinforced silicone membrane (Davis et al., 1983a).

Adult females readily ingested bovine blood through the membrane thus

eliminating the need for live laboratory animals or human hosts. This

information will be useful when attempts are made at colonizing C.

mississippiensis in the laboratory.

Other studies in the Yankeetown area have been directed at

controlling the adult and immature stages. Roberts and Kline (1980)

developed a trap for use in testing insecticides as household screen

treatments. They used the trap to test the effectiveness of

chlorpyrifos, fenthion, malathion, and propoxur for controlling C.

mississippiensis adults (Kline and Roberts, 1981). Propoxur and

chlorpyrifos caused 97-100% mortality for 35 days when applied to 16 by

18 mesh aluminum screen; however, the former was considered more

effective because of its quick knockdown characteristic. Fenthion was

ineffective as a screen treatment and also when used in wind tunnel tests

against the same species. Six other pesticides, all effective for

mosquito control, were evaluated in the wind tunnel (Kline et al.,

1981a). Pyrethroids produced a better knockdown than the

organophosphates tested.

Personal protection measures have not been overlooked in the

examination of control methods. Nets were treated for use in 2 types of

situations. The first was in the form of a jacket that could be worn by

an individual for protection while working in areas infested with biting

midges (Schreck et al., 1979a). When treated with N, N-diethyl-m-

toluamide deett), the jacket provided 98-99% protection against C.

mississippiensis, C. furens, and C. hollensis. The second was the use of

treated net as area protection (Schreck and Kline, 1983). The

deet-treated net covered an 18 m area and offered protection to people

for up to 4 days.

Workers have also examined materials applied topically to the skin.

Five new chemicals (Schreck et al., 1979b) and 4 commercially available

"home remedies" (Schreck and Kline, 1981) were compared with a deet

standard. Two of the new products, which were synthesized by the USDA

Laboratory in Beltsville, Maryland, and all of the commercial products

were as good as or better than deet. Mineral oil, AvonN Skin-So-Soft,

Johnson'sT Baby Oil, and Claubo prevented the flies from biting but did

not act as repellents. The oiliness of the materials trapped the insects

on the skin before they had a chance to bite.

All of the above control techniques have been tested against adult

biting midges. The treatment can be costly because adults often fly in

from untreated areas within a short time after the midge population has

been reduced and retreatment is necessary. Control of the immature

stages is an alternative that may be less expensive in some situations.

Chlorpyrifos, fenthion, temephos, and malathion were tested as potential

larvicides (Kline, 1984). The LD50 for chlorpyrifos was much lower than

the other materials thus it was the most toxic. Fenthion and temephos

are also worthy of further testing in the field but malathion had such a

high LD50 that it probably would not be feasible for use as a larvicide.

In other tests, Bacillus thuringiensis serotypee H-14) de Barjac was

evaluated and found to be ineffective for controlling larvae of C.

mississippiensis, C. guttipennis, C. variipennis, and Leptoconops spp.

(Lacey and Kline, 1983). The bacterium was ingested in sufficient

quantities to produce mortality but, apparently, the larvae are not

susceptible to the 6-endotoxin. Another biological agent, a Nosema type

of microsporidian, was found naturally occurring in 3rd and 4th instar

larvae of Culicoides spp. near Yankeetown (Kline et al., 1985). This was

the first report of a microsporidian species found in any estuarine

species of Culicoides.



1. To determine the diel and seasonal abundance of Culicoides spp.

that bite man along the Gulf Coast of Florida.

2. To examine the relationship between the phases of the moon and

Culicoides activity (i.e., lunar periodicity).

Research Site

A research site was selected near Yankeetown, Florida, in Levy

County (Figure 1). Biting midges are extremely abundant in the area and

the USDA Insects Affecting Man and Animals Research Laboratory has been

conducting studies there since 1977. Extensive saltmarshes serve as

ideal sites for the development of immature biting midges.

Materials and Methods

The methods of Bidlingmayer (1961) and Barnard and Jones (1980b)

were used. The 24 h cycle was divided into 20 periods (Figure 2) based

upon the times of sunrise, sunset, and nautical twilight which were
obtained from the U.S. Naval Observatory Sunrise and sunset occur when

the upper edge of the sun's disk appears to be on the horizon. Nautical

U.S. Naval Observatory, 34th and Massachusetts Ave., NW,
Washington, D.C. 20390.



o a





0 0


H 4J

H (


= 0




twilight occurs when the sun is 120 below the horizon. The use of these

times as reference points throughout the study was necessary to account

for changes in the duration of the photophase (daytime) and scotophase

(nighttime) that occur during the year. The photophase was represented

by 10 equal periods. Period 1 began at sunrise and period 10 ended at

sunset. Evening twilight began at sunset, ended at the end of nautical

twilight, and consisted of a single period, 11. The scotophase was made

up of 8 equal periods. Period 12 began at the end of evening twilight

and period 19 ended at the start of morning twilight. The final period,

20, represented morning twilight; it lasted from the end of scotophase

until sunrise.

The duration of each period in the photophase ranged from 62-84 min,

the twilight periods ranged from 52-60 min, and each period of the

scotophase ranged from 60-90 min.

The sampling strategy was implemented on 1 day of the quarter

phases of the moon (i.e., new moon, first quarter moon, full moon, and

last quarter moon) from 26 May 1983 to 5 July 1984 (Table 1). A

vehicle-mounted trap (Holbrook and Wuerthele, 1984) was used as the

sampling device (Figure 3). This specific trap design was selected

because the front of the trap is mounted over the hood of the vehicle

rather than the cab such as that of Barnard (1979). I computed the times

for collecting 3 samples within each period by establishing the midpoint

as one collection time and 20 min either side of the midpoint for the

other 2 collection times. Thus 60 samples were collected in a 24-h

period approximately every 7 days. A total of 3,360 samples were

obtained with the vehicle-mounted trap throughout the study.

Table 1. Sample collection dates on 1
in 1983-84.

day of quarter phases of moon

New Moon First quarter Full moon Last Quarter


26 May 3 Jun
10 Jun 17 Jun 25 Jun 3 Jul
10 Jul 16 Jul 24 Jul 2 Aug
8 Aug 15 Aug 22 Aug 31 Aug
5 Sep 12 Sep 21 Sep 28 Sep
5 Oct 12 Oct 21 Oct 29 Oct
5 Nov 12 Nov 19 Nov 26 Nov
3 Dec 10 Dec 18 Dec 26 Dec


3 Jan 11 Jan 18 Jan 25 Jan
1 Feb 9 Feb 16 Feb 24 Feb
2 Mar 10 Mar 17 Mar 24 Mar
31 Mar 7 Apr 15 Apr 23 Apr
30 Apr 8 May 15 May 22 May
30 May 6 Jun 13 Jun 21 Jun
28 Jun 5 Jul













The trap was mounted on a 4-speed 1983 Ford Ranger pickup truck

that was provided by the USDA Insects Affecting Man and Animals Research

Laboratory. The truck was driven over a 4.0 km route on an oyster shell

road through a saltmarsh (Figure 4A). On 29 October 1983, I modified the

route at the request of local residents but the distance traveled for

each collection remained the same by completing 2 round trips of a 2 km

circuit (Figure 4B). The route was completed in 10 min at a speed of

25-30 km/h. The vehicle lights were operated at the dim setting for each

collection during periods 11-20. A collection bag made of nylon insect

netting at the rear of the trap was detached and labeled after completing

the trap route. Debris that accumulated in the trap, anterior to the

collection bag, was discarded after periods 11 and 20.

At the end of each period I also collected all Culicoides spp. that

were attracted to my left forearm during 5 min. This provided a measure

of host-seeking activity or landing rate because most individuals were

collected before they inserted their mouthparts. A hand-held aspirator

was used and a light was operated during the collection in periods 11-20

(Figure 5). Biting midges attracted to other areas of my body were not

collected but records were kept of the intensity of the activity over all

exposed areas. Personal insect repellents or insecticides were never

used. Twenty samples were collected with the aspirator during a diel

cycle and 1,120 were obtained during the entire study.

Both the vehicle-mounted trap collections and the host-seeking

aspirator collections were stored in a container with solid CO2 (i.e.,

dry ice) for transport back to the laboratory in Gainesville. Individuals

in the genus Culicoides were sorted and identified to species and sex.

All specimens were stored in 75% ethanol for later use.

Hwy. 40A

(A) V

r/stFp -- -
o Weather (4km)

- County Highway
Oyster Shell Road
Private Road

0 0.3 km

To Yankeetown --

-- "` ----'-/start
stop -------
Weather (2km)

To Yankeetown-)

Vehicle-mounted trap route. A. Initial 4 km circuit.
B. Final route driven 2 round trips per collection.

Figure 4.

^ ;









. . .


In addition to the above sampling program, environmental conditions

were monitored. Temperature (oC) and wet bulb depression were measured

after every vehicle-mounted trap collection by using a hand-held sling

psychrometer. Light intensity (foot candles) was measured at the same

time by using an International Light model IL710A Research Photometer.

A weather station was set up at the research site to monitor wind speed

and wind direction throughout the study (Figure 4).

All data from the vehicle-mounted trap program were recorded on a

data collection form (Figure 6) to aid in computer entry. Abbreviations

were used for some information on the form to reduce the amount of

material entered. The term 'period' referred to collection periods 1-20

and the term 'sample' referred to the 3 samples (A, B, or C) collected in

each period. The time that a specific sample was collected was entered

as start time. Moon phase was abbreviated as NM, FQ, FM, and LQ for new

moon, first quarter, full moon, and last quarter, respectively.

Abbreviations for seasons were P (spring), S (summer), F (fall), and W

(winter). All samples were assigned a collection number in the order

they were obtained. Each collection number was recorded on the

collection bag, at the bottom of the collection form, and at the end of

the specific line of computer entry for all data associated with a given

sample. The collection number served as a means of cross-indexing these

3 aspects of record keeping. Data from the host-seeking study were

recorded in a field notebook. Records were entered into the University

of Florida computer system and analyzed by using the Statistical Analysis

System (SAS) packaged programs. An analysis of variance (ANOVA) and

Duncan's multiple range test were used as part of the General Linear

Models procedure (Goodnight et al., 1982). The statistical significance

day month year period sample

hours minutes


WIND m/sec

Culicoides spp.
C. mississippiensis

C. barbosai


C. floridensis

EMP. _._C HUMIDITY__ __%

direction foot candles

males females


Figure 6. Data collection form used to record all data from
vehicle-mounted trap program.

level for accepting the hypothesis of ANOVA tests was p<0.01 and of

Duncan's tests it was p<0.05. The analysis included a comparison of the

number of individuals of each species collected during different

collection periods, phases of the moon, and seasons of the year.

Distinction between the four seasons was based on dates of the summer and

winter solstices and the spring and fall equinoxes.

Results and Discussion

Relative Abundance

Culicoides mississippiensis, C. furens, C. barbosai, and C.

floridensis Beck were found to bite man near Yankeetown, Florida. A

total of 9,563 specimens were obtained in the host-seeking collections.

The majority of individuals (79.1%) were C. mississippiensis (Table 2).

This species was most abundant in the spring (33.8%) when biting activity

in general was greatest (38.1%). The least common host-seeking species

was C. furens (2.8%).

The four species taken in the biting collections were represented in

the vehicle-mounted trap collections but in different frequencies

relative to one another (Table 3). Culicoides mississippiensis was the

most common, represented by 65.7% of the 291,346 specimens collected.

Kline (1984) also found it to be the most prevalent species of Culicoides

in the Yankeetown area based on light trap collections. The least common

biting species, C. furens, was the second most abundant (29.6%) in the

trap. Only 1% of the individuals obtained in the trap was C.

floridensis. The low percentage of this species does not accurately

reflect its frequency as a pest of man in the area (Table 2).

Table 2. Relative frequencies for
the arm of a human host.
individuals collected.)

4 species of Culicoides attracted to
(Each value is a percentage of 9,563

a b Total by
Season C. miss. C. furens C. barb. C. floor. season





Total by





















a C. miss.

C. barb.
C. floor.

C. mississippiensis
C. barbosai
C. floridensis

(n U)
m LA
* *

0o n


N 00
0 0

o o




HI 4

U) -rH


C) .d




44 (a

0 0)





*H 0O








H -*
4J O)
E- u)

H m 0
,_ n

0 0

0 0

0 0

M 4
0 rH CM

The 291,346 specimens obtained in the vehicle-mounted trap included

56,235 males. The seasonal changes in the frequency of males followed

that of the females but at a much lower level (Table 3). Culicoides

floridensis males were rare in the collections. Only 31 males of this

species were obtained and 28 of these occurred during the summer.

An analysis of variance showed that there was a significant

difference (p<0.01) between the number of individuals collected during

the different collection periods. The activity also varied significantly

(p<0.01) from one season to the next and with the phases of the moon

(p<0.01). Further analysis by using Duncan's test indicated which

periods, seasons, or phases of the moon differed significantly (p<0.05).

An examination of the interaction between the main effects indicated that

the relationship between collection period, moon phase, and the number of

specimens collected was not the same for each season (p<0.01).

Seasonal Occurrence

Culicoides mississippiensis was active throughout the year (Figure

7). The number of males increased rapidly during January and February

and reached a peak in March. The occurrence of C. mississippiensis

females did not climax until late May and it declined rapidly during the

hotter months of the year. Females were also abundant in early November

but did not reach the same level as in May. The November peak was

proceeded by an increase in the number of males in October. The seasonal

distribution of the females observed during this study is in agreement

with light trap data reported by Beck (1958) and Khalaf (1969). Prior

reports of male activity did not exist.

The activity of C. furens was limited to April through October

(Figure 8). The frequency of males and females parallel one another when





S----" Females
- Males




Figure 7. Seasonal incidence of C. mississippiensis adults
collected in a vehicle-mounted trap.


---. Females


I \ \
I \ I \

-I \

/ 2- I \ / \
SI \ \
-I \ \

I \\
z ;I

w[ I

0 I \
( ID


J F M A M J J A S 0 N D

Figure 8. Seasonal incidence of C. furens adults collected in
a vehicle-mounted trap.

presented graphically, but the females were collected in greater

quantities. Kline and Roberts (1982) conducted a light trap survey about

300 km south of Yankeetown near Punta Rassa, Florida (Figure 1) and found

that C. furens was present from March to December. The species was

active in North Carolina (Kline and Axtell, 1976) from May through

September, but in New York state it was abundant only during the month of

July (Jamnback, 1965). The decrease in activity as latitude increases

was also noted by Blanton and Wirth (1979) and they referred to it as

northern displacement. Changes in photoperiod and temperature that

accompany changes in latitude probably regulate the duration of activity.

Culicoides barbosai (Figure 9) and C. floridensis (Figure 10) were

less abundant than the other two species in the vehicle-mounted trap

collections. The former was present from April through October with

distinct peaks in May, July, and October. Males of C. barbosai were not

abundant in the trap but the activity of the few specimens obtained (529)

coincided with peaks observed for the females (Figure 9). This species

appears to be less abundant in the Yankeetown area than in parts of Lee

County, Florida (Beck, 1958; Kline and Roberts, 1982), but the general

incidence of activity is in agreement.

The occurrence of C. floridensis females was practically restricted

to the summer months and only 31 males were collected during the entire

study (Figure 10). Apparently the vehicle-mounted trap is a poor method

of sampling the C. floridensis population. Perhaps this species does not

frequent open areas such as roadways or it does not fly at the elevation

sampled by the trap. Light traps were used in a prior study (Beck, 1958)

but only in Highlands County, Florida, was this species collected in





z I




----a Males

I ~







J F M A M J J A S 0 N D


Figure 9. Seasonal incidence of C. barbosai adults collected in
a vehicle-mounted trap.


/ I



*---- Females

J F M A M J J A S 0 N C


Figure 10.

Seasonal incidence of C. floridensis females collected
in a vehicle-mounted trap.

/ '
I '
/ '






sufficient numbers to evaluate. The activity in that area began in

mid-May and ended in early September.

Diel Periodicity

Time of day relative to sunrise and sunset during which adults were

active was not the same for all species or the sexes. Activity of a

given species varied from one season to the next and with the phases of

the moon.

Females of C. mississippiensis were most active during collection

periods 2, 10, 11, and 20 (Figure 11). During the summer their activity

declined rapidly after sunrise and fell to zero in period 4. Flight

resumed just before sunset, peaked during evening twilight, and gradually

decreased during scotophase. The spring pattern was very similar but

more individuals were present and flight activity occurred throughout the

24 h cycle. The greatest frequency, like in the summer, was observed

during evening twilight. During fall and winter, the increase in female

activity began earlier in the day relative to sunset and reached a

maximum in period 10 rather than the twilight period. The response was

probably related to temperature. Mean temperature in period 10 in the

winter was 15.10C while in period 11 it was 13.90C.

A seasonal shift in peak activity did not occur for males of C.

mississippiensis (Figure 12). They were always most active just after

sunset during period 11. In summer, fewer individuals were collected

than during any other season and their flight was restricted to this

period. Males remained active throughout scotophase during the spring

but not in the fall and winter. They were inactive during early morning

hours prior to sunrise in those seasons. Males of C. mississippiensis

----* Spring
I----- Summer

So.......o Fall
* ** ---- Winter

i :\



2 4 6 8 10

12 14

16 18 20

Figure 11.

Diel periodicity of C. mississippiensis females
collected in a vehicle-mounted trap during
different seasons.

< 2
( I

*---- Spring
Ia Summer
o........o Fal

-. Winter

P/ \
i \

"1 \
I \

2 4 6 8 10

Figure 12.

12 14

16 18 20

Diel periodicity of C. mississippiensis males
collected in a vehicle-mounted trap during
different seasons.

were active for less of the diel cycle than females, especially during

the summer.

The total number of females was usually greater than the number of

males but at certain times of the day such as just after sunset the males

actually outnumbered the females by as much as 3:1 (not illustrated).

This was especially true in late March, early April, and late October

when the males were most abundant. Mating swarms have been observed for

C. mississippiensis around sunset (D.L. Kline, personal communication)

and such activity may explain the change in sex ratio. Nathan (1981)

observed swarms of C. phlebotomus being intercepted by a vehicle-mounted

trap in north Trinidad and the male to female ratio changed drastically

during such instances.

The ratio of male to female C. furens was also about 3:1 just after

sunset during months of greatest male activity, May and August. In

general, both sexes appeared together in large numbers during the evening

twilight of spring, summer, and fall and during the morning twilight of

summer (Figures 13 and 14). The evening peak was consistently greater

than the morning peak. Females (Figure 13) did not undergo seasonal

shifts in their bimodal periodicity but males did (Figure 14). In

spring, the nighttime flight activity of the males declined through

morning twilight and did not increase until period 1, immediately after


Koch and Axtell (1979) also observed a larger evening peak for C.

furens females in suction trap collections in coastal North Carolina but

Bidlingmayer (1961) collected more females during the morning by using a

vehicle-mounted trap near Vero Beach, Florida. Males were not collected

in sufficient quantities to evaluate in either study. Kline and Roberts

6----* Spring
-- Summer

.......... Fall


< 2-


z -
z -





I -

T r- 1 r T" I I I I I I I I I I I I 1 1 1
2 4 6 8 10 12 14 16 18 20

Figure 13. Diel periodicity of C. furens females collected in
a vehicle-mounted trap during different seasons.


/ 0




- Summer

........ Foal I

2 4 6 8 10


Figure 14.


14 16 18 20

Diel periodicity of C. furens males collected in a
vehicle-mounted trap during different seasons.







I' 3
I~ j



(1982) did not obtain enough of either sex of C. furens near Punta Rassa,

Florida, to make an assessment of their diel periodicity.

Females of C. barbosai were active primarily during the twilight

periods, but, unlike C. furens and C. mississippiensis, the morning peak

was greater than that at dusk (Figure 15). Kline and Roberts (1982) also

observed a higher level of activity in the morning for this species near

Punta Rassa, Florida. They used a non-attractant device, a suction trap,

to sample the population. Near Yankeetown, the females were active

during scotophase in the spring only. Activity increased prior to

sunrise and the females remained active for about 2-3 hours after that

time. Additional activity during photophase occurred only in the fall.

Major peaks of male flight activity (Figure 16) coincided with those of

the females. Males were also more abundant at dawn than at dusk but only

during the summer. Neither sex of C. barbosai was active during the


Culicoides floridensis was collected in low numbers during late

spring and early summer. Females were active during most of the diel

cycle (Figure 17). In general, their activity was crepuscular and

nocturnal with peaks of approximately equal amplitude immediately after

sunset and just before sunrise. Too few males were taken to provide an

accurate evaluation of their diel periodicity. Of the 31 males collected

throughout the study, 10 were obtained during period 20, 5 during each of

periods 1 and 10, and the remainder during scotophase.

Lunar Periodicity

Adult females of C. mississippiensis, C. furens, and C. barbosai

were active for a greater duration of the scotophase and in greater

numbers when the moon was full. The occurrence varied seasonally. Males

S---- Spring

- Summer

o ...... o Fall

*. b
: .
I .*' ** /

2 4 6 8 10 12 14 16 18 20



Figure 15.

Diel periodicity of C. barbosai females collected in
a vehicle-mounted trap during different seasons.

- Summer

o........o Fall


1. : 1 \
:" \l / '

\ ",i \

2 4 6

12 14 16 18 20


Figure 16.

Diel periodicity of C. barbosai males collected in
a vehicle-mounted trap during different seasons.

S--- Spring
S Summer


~ 1

2 4 6 8 10 12 14 16 18 20



Figure 17.

Diel periodicity of C. floridensis females collected
in a vehicle-mounted trap during different seasons.


'b -

of these species did not show the same relationship (Figure 18). The

combined data for the three species indicates that the diel periodicity

of the males did not change significantly relative to the phase of the

moon. This differed from C. crepuscularis and C. variipennis in

northeastern Colorado where both sexes were active in greater numbers

when the moon was full (Barnard and Jones, 1980b).

More C. mississippiensis females were caught when the moon was full

in spring (Figure 19) and summer (Figure 20) than in fall (Figure 21) and

winter (Figure 22). The number of individuals in flight peaked during

period 11, declined in periods 12 and 13, but changed very little after

that time when the moon was full (Figures 19 and 20). The amplitude

continued to decrease after period 13 when the moon was in some other

phase. During last quarter moon, female activity began to increase when

the moon rose midway through scotophase (ca. period 16). Barnard and

Jones (1980b) also reported an increase in the abundance of Culicoides

spp. at the time of moonrise in northeastern Colorado. Bidlingmayer

(1967) observed the same phenomenon for mosquitoes in Florida. Another

noteworthy association with the moon was a rapid decrease in female

activity at the time of moonset (ca. period 16) during the first quarter

phase (Figure 19).

Light intensity may have regulated flight activity during

scotophase; however, other factors were most likely important because new

moon collections often surpassed those of first and last quarter phases

(Figures 19 and 20). Temperature was probably a critical factor in the

fall (Figure 21) and winter (Figure 22) because the activity of biting

midges declined rapidly as the temperature decreased after sunset. The

number of individuals often increased again during period 15, 16 or 17,

0....... New Moon
----- First Quarter
*---* Full Moon

Last Quarter

2 4 6 8 10 12 14 16 18 20


Figure 18. Diel periodicity of male Culicoides spp. collected
in a vehicle-mounted trap on quarter phases of moon.


..J 2




o.......o New Moon
----- First Quarter

- Full Moon
-- Last Quarter

o 0

o... o


/ II



4 6 8 10



1 I I I
14 16


Figure 19.

Diel periodicity of C. mississippiensis females
collected in a vehicle-mounted trap on quarter
phases of moon in the spring.







....... o New Moon
*---" First Quarter
*---* Full Moon
SS --- Last Quarter







2 4 6 8 10 12 14 16 18 20

Figure 20.

Diel periodicity of C. mississippiensis females
collected in a vehicle-mounted trap on quarter
phases of moon in the summer.


3^1 I

S.........o New Moon
----* First Quarter
* Full Moon
Last Quarter





2 4 6 8 10 12 14 16 18 20

Figure 21.

Diel periodicity of C. mississippiensis females
collected in a vehicle-mounted trap on quarter
phases of moon in the fall.

-...... New Moon
*--- First Quarter
--- Full Moon
- Last Quarter

2 4 6 8 10 12 14

Figure 22.

16 18 20

Diel periodicity of C. mississippiensis females
collected in a vehicle-mounted trap on quarter
phases of moon in the winter.






but it did not persist, even following moonrise, for the duration of the

night. In winter, the adults were active for less of the scotophase than

in other seasons (Figure 22).

The relationship between moon phase and C. furens activity was

similar to that of C. mississippiensis during the spring (Figure 23) and

summer (Figure 24) only. Specimens were collected in great quantity

throughout the night when the moon was full. Also, an increase in

activity followed moonrise while a decrease in activity followed moonset

(ca. period 16). In fall, C. furens activity (Figure 25) was similar to

that of C. mississippiensis (Figure 21) by showing an increase during

period 15 or 16, but the 2 species differed in their relationship with

full moon in that season. Culicoides furens were taken in large numbers

on some occasions in the fall when the moon was full but not always. The

mean for full moon collections was less than or equal to the means for

new and last quarter (Figure 25). Bidlingmayer (1961) also reported an

inconsistent pattern with respect to moon phase and C. furens activity in

Florida. He conducted his study during the summer and fall of 1959 and

found that the number of females collected during scotophase was not

always greatest when the moon was full.

The association with full moon and female activity did not fluctuate

with the seasons for C. barbosai. The number of individuals in flight

was always highest when the moon was full, therefore, the data were

combined for all seasons (Figure 26). The adults were virtually absent

between periods 14 and 19 during new, first quarter, and last quarter

moon. The amplitude of the nighttime collections of this species during

full moon was approximately 20 times greater than during other phases.

0o........ New Moon
SS ,---. First Quarter
4 -- Full Moon
-- Last Quarter



2 4 6 8 10 12 14 16 18 20

Figure 23.

Diel periodicity of C. furens females collected in
a vehicle-mounted trap on quarter phases of moon
in the spring.






. i0


.......... o New Moon
.----. First Quarter
Full Moon
-- Last Quarter

1 I i i I
8 10

12 14

Figure 24.

Diel periodicity of C. furens females collected in
a vehicle-mounted trap on quarter phases of moon
in the summer.






.. YI




I 8

2 1


J l % .

0........o New Moon

2 4 6 8 10

Figure 25.

12 14 16 18 20

Diel periodicity of C. furens females collected in
a vehicle-mounted trap on quarter phases of moon
in the fall.






2 4 6 8 10 12 14 16 18 20



Figure 26.

Diel periodicity of C. barbosai females collected in
a vehicle-mounted trap on quarter phases of moon.

The occurrence of C. floridensis when the moon was full did not

differ significantly (p>0.05) from new and first quarter moon collections

(Figure 27). A possible reason for such behavior is that this species is

active for only a brief portion of the year (Figure 10) compared to the

other species. Individuals may cue on some environmental factor other

than moonlight to regulate their nighttime activity. Another possible

explanation is the bias of the vehicle-mounted trap as a collection

device for C. floridensis. Fewer specimens were obtained in the trap

(Table 3) than in aspirator collections (Table 2).

Diel and Seasonal Host-Seeking Activity

The diel periodicity of host-seeking specimens did not always agree

with that of specimens collected in the vehicle-mounted trap. The most

likely reason for this occurrence was that the two sampling methods

procured different populations of a given species. Aspirator collections

contained individuals seeking a bloodmeal. In contrast, the

vehicle-mounted trap did not employ an attractant and was much less

selective. The trap contained adults in search of an oviposition site or

a mate as well as those seeking a host. The most apparent difference was

that the vehicle-mounted trap collected both sexes while only females

were obtained with the aspirator. Bidlingmayer (1961) encountered

similar disparities in the two sampling techniques.

The number of C. mississippiensis attempting to engorge was greatest

just before sunset (Figure 28). The rate of attack was unbearable at

this time, particularly in the spring. As many as 190 specimens were

collected from the forearm over a 5 min interval in late March. Biting

was also intense on other exposed areas of the body especially the face

and neck. Few specimens attacked during the first 2 min of exposure but





_ -j

SS '. ....... New Moon
S----- First Quarter
O-* Full Moon
/ *. --- Last Quarter

1 "o

II .
: I.

: I
i; \ ,?
-, A- \ ,:

I ~ ~~ !o....-

2 4 6 8 10

Figure 27.

12 14 16 18 20

Diel periodicity of C. floridensis adults collected
in a vehicle-mounted trap on quarter phases of moon.

---- Spring

2 4 6 8 10 12 14 16 18 20

Figure 28.

Diel host-seeking activity of C. mississippiensis
during different seasons.