Within Florida, this fly was first collected in 1949 in Escambia County, the western-most county of that state's panhandle. Today, it is found throughout Florida. With numerous variations, it is a widely held myth that University of Florida entomologists introduced this species into Florida. However, Buschman (1976) documented the progressive movement of this fly species around the Gulf Coast into Florida. Research was conducted by University of Florida and U.S. Department of Agriculture entomologists only after the lovebug was well established in Florida.
Hetrick (1970a) stated that adult males lived for two to three days and that females may live for a week or longer and mate with more than one male. However, Thornhill (1976c) recorded recapture data that showed males lived longer in the field than females. In his study, single females were collected up to four days after release while single males were collected five days after release.
The females lay gray, irregularly-shaped eggs in or on the soil surface under partially decayed vegetable matter. Slate-gray larvae are often found in groups where moisture under the decaying vegetation is constantly present. Factors necessary for larval survival include adequate moisture, partially decayed vegetation (for food), and favorable soil temperatures. Pupation occurs where the larvae develop, with the pupal stage lasting seven to nine days (Hatrick 1970a).
Each of two generations of adult P. nearctica in Florida lasts about four weeks in April-May and August-September. In addition to the two large emergences this species has been collected in Florida every month of the year except November (Buschman 1976). A more recent study by Cherry and Raid (2000) shows a minor flight peak in December for south Florida that had been previously unrecorded. This later study does not contradict the importance of the two major flight peaks earlier in the year, but does states that in south Florida most of the adults seem to appear in April during the first yearly flight.
Buschman (1976) stated that, throughout its extensive range, P. americana has been collected only in April, May, and June, with no evidence of a fall emergence. Thus, Plecia that emerge in the fall are definitely P. nearctica. Thompson (1975) added that most of the spring collection dates of P. americana in north central Florida are two or three weeks earlier than similar dates for P. nearctica.
1. Thorax with dorsum rufous and pleura extensively black; head with oral margin distinctly produced forward . Male genitalia with 9th tergum not as broad as in americana, just slightly broader than long, with shallow medial excavation and ventromedial flap, not produced ventrolaterally; 9th sternum with dorsolateral lobe extending under 9th tergum, produced ventromedially into a narrow forked process; telomeres large, L- shaped in lateral view. Female genitalia with 9th tergum large, almost completely concealing cerci in lateral view, strongly excavated dorsomedially; cerci small, narrow in dorsal view; 8th sternum small, with a shallow medial excavation; ovipositor lobes broad, blunt apically and strongly sclerotized dorsally . . . . . lovebug, P. nearctica Hardy
1'. Thorax almost completely rufous, rarely slightly brownish black on metathoracic pleura; head with oral margin not produced forward, but evenly convex. Male genitalia with 9th tergum much broader than in nearctica, almost twice as broad as long, with a deep medial excavation and without a ventromedial flap, ventrolateral corners produced posteriorly; 9th sternum with a dorsolateral lobe, not produced ventromedially and without a medial forked process, but with a broad ventromedial excavation; telemeres small, almost completely round. Female genitalia with 9th tergum small, not concealing cerci in lateral view, not excavated medially; cerci large, broad in dorsal view; 8th sternum large, with a deep and narrow medial excavation; ovipositor lobes narrow, acute apically, not strongly sclerotized dorsally . . . . . P. americana Hardy
Dilophus sayi is smaller than the Plecia spp., and has an all-black body, lacking the reddish color of the thoracic region of Plecia. The males of D. sayi are smaller than the females and have clear wings as apposed to the brown fumose wings of the females.
Dilopus sayi was observed being attracted to recently parked cars in Gainesville, Florida, and to barbecue grills (Denmark and Mead, personal observations). Thornhill (1976a) in studies at Gainesville, Florida stated that aggregates of up to 300 larvae of D. sayi could be found on or near the surface of the soil among the roots of grasses. Under lab conditions adult females lived about 72 hours and adult males about 92. Both Thornhill and Rothamel (1969) gave details on orientation and coupling of D. sayi. This bibionid attains nuisance numbers as adults in Florida and elsewhere from South Carolina south and west to Texas and California. Complaints about the larvae and adults of D. sayi (reported as D. orbatus, an earlier name) were statewide in California during October of 1970 (USDA Cooperative Economic Insect Report 20797). In this same volume, there were numerous reports of it being a problem during autumn in sod and lawns, including one report of 1,000 larvae per square meter in a nursery at Oakland, Alameda County, California. However, this species is of minor importance compared to P. nearctica, which can be a nuisance on Florida highways.
Callahan and Denmark (1973) reported that ambient temperatures above 28°C and visible light at above 20,000 Lux (2000 ft-C) stimulated lovebug flight but not orientation behavior. Lovebugs are attracted to irradiated automobile exhaust fumes (diesel and gasoline) when the ultraviolet light incident over the highway ranges from 0.3 to 0.4 microns (3000 to 4000 angstroms (A)) between 10 AM and 4 PM, with a temperature above 28°C. Hot engines and the vibrations of automobiles apparently contribute to the attraction of lovebugs to highways. Solar radiation below 2.9 microns (2900 A) does not penetrate the atmosphere. Callahan et al. (1985) reported that formaldehyde and heptaldehyde were the two most attractive components of diesel exhaust.
The following description of reproductive behavior was taken largely from Leppla et al. (1974), who reported on a daily rhythmicity of flight, mating, and feeding of lovebugs in the laboratory and in the field, which coincided with the ambient temperature of 19°C and an incident light intensity range of 15,000 to 20,000 Lux (1500-2000 ft-C). Adult males begin hovering between 8:00 to 10:00 AM EDT. Males orient into the wind 0.3 to 0.9 meters above ground level. This behavior tends to cease after 10 AM and a resurgence occurs at 4:00 to 5:00 PM and lasts until about 8:00 PM. Females do nor hover but crawl up vegetation and take flight through the swarm of hovering males. The female is grasped by a male during flight, or while she is on vegetation before flight. Copulating pairs begin dispersal flights around 9 to 11 AM. Individuals may feed alone, or while in copula, on nectar or pollen in the vicinity of the emergence site. There are few or no mating pair flights by afternoon.
By using traps 12.5 x 9.1 meters in area, it was determined that most lovebugs emerge from the pupal stage from 6 to 9 PM with a smaller number emerging from 8:00 AM to 12 Noon (Thornhill 1976b). Eclosion from the pupal stage requires about 5.2 hours at 27°C for males and six hours for the females. Both sexes become fully sclerotized within two hours. Thornhill (1976b) did not report any positive evidence for the emission of a sex pheromone by either sex during or proceeding copulation. Males apparently hover near their emergence sits and use visual and perhaps auditory cues to locate the opposite sex.
Copulatory behavior begins with the male darting and grasping a female that is flying through the swarm. The pair falls to the ground where they couple. Initially the male is positioned on the back of the female and both sexes face the same direction. After coupling, the male turns 180° and faces the opposite direction. Successful genitalic engagement takes from 1.5 to 10 min. There is intense competition among males for females at emergence sites. Hovering males may grasp and attempt to disrupt copulation pairs flying in the vicinity. Larger males are more successful in disrupting copulating pairs. It was also observed that the larger females laid more eggs, but the average is about 350 eggs per female (Hetrick 1970a).
Marked copulating pairs were collected up to three days after their release. In nature, pairs were never observed to disengage in flight or at night, but termination was observed in the daytime on vegetation. Second matings were observed in the laboratory when a virgin of the opposite sex as provided. Females that mate once usually lay their eggs and die after an average of 68 hours. Females that mated twice before laying eggs lived for a mean of 86 hours. Maximum sperm transfer requires about 12.5 hours.
Other habitats recorded for populations of P. americana include live oak hammocks, wooded ravines, and deciduous forests.
The adult flies are a nuisance to motorists because the flies are attracted to highways and spatter on the hood and windshield of vehicles. Large number of lovebugs can cause overheating of liquid-cooled engines by clogging radiators, reducing visibility, and etching automobile paint as the body fluids are slightly acid. However, if the egg mass and body parts are allowed to remain on the vehicle for several days, bacterial action increases the acidity and etches the paint. A soaking with water for about five minutes followed by a scrubbing within 15 to 20 minutes should remove most of the lovebugs without harm to automobile paint.
Fortunately, improvements in vehicle paint coatings have made this less of a problem. A hood air deflector will reduce the number of spattered lovebugs on a vehicle. In addition, specially designed nylon screening, with hooks that quickly attach to the front of vehicle bodies, protecting the radiator grill and front horizontal surfaces) are commercially available at automotive supply stores. The screens catch the flies, preventing radiator clogging and splattering on the vehicle body. The screens are easily removed for cleaning with a waterhose.
The adults seem to be attracted to light-colored surfaces, especially if they are freshly painted. For several decades after the 1940s, the painting of exterior building surfaces was often suspended during the adult flights (Hetrick 1970).
adults on light-colored surface
The degree of natural control and the amount of annual rainfall causes fluctuation in populations.
Kish et al. (1974) isolated and identified five species of fungi from dead lovebugs collected in Florida during April and May. These fungi were:
Nine additional fungi were reported from dead or moribund larvae collected in the field. These fungi are likely important in the natural control of lovebugs (Kish et al. 1977). Further study is needed to determine how these fungi or other organisms may be used to control lovebugs.
Authors: H.A. Denmark (retired) and F.W. Mead (retired), Florida Department of Agriculture & Consumer Services, Division of Plant Industry; and T.R. Fasulo, University of Florida
Originally published as DPI Entomology Circular 350. Updated for this publication.
Photographs by: James Castner and Lyle J. Buss, University of Florida; Debra Young
Drawings of head, wings and genetalia: F.C. Thompson, University of Florida
Project Coordinator: Thomas R. Fasulo, University of Florida
Publication Number: EENY-47
Publication Date: August 1998. Latest revision: November 2008.
Copyright 1998-2008 University of Florida
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swarm on flowers
swarm on building
car windshield
larvae
heads and wings
male genitalia
female genitalia
adults in copula
car headlight
car body
adults on painted surface
adults on painted surface