Lovebugs, Plecia nearctica, are a biological scourge that arises in Florida and other southeastern states each spring and again in the fall.  During these seasonal appearances, these small black flies with red upper backs are so infuriatingly numerous that they bring to mind the grievous swarms of flies and locusts that, according to the Book of Exodus, plagued the people of Egypt, their houses, covered the face of the earth, and corrupted the land.  Are Floridians suffering a biblical punishment?  Indeed, where did lovebugs come from and why are they here? 
One persistent myth claims that lovebugs escaped from University of Florida entomologists, who were trying to get rid of mosquitoes.  One version of the story claims they escaped before they could be genetically engineered to feed on mosquitoes.  Another version asserts that they escaped before they could be crossed with mosquitoes to produce sterile offspring.  Both stories are false.  Adult lovebugs are not carnivores, they feed on plant material, and they will not mate with mosquitoes. 
Lovebugs were first described from Galveston, Texas, in 1940, when they extended as far south as Costa Rica and already were widespread in Texas, Louisiana, and Mississippi.  In 1947, they spread into Escambia County in Florida’s far western panhandle.  They reached Alachua County in 1956, and Sarasota in 1972.  By 1974, they were in the Homestead area of south Florida and much of Georgia, South Carolina and North Carolina
The primary function of adult lovebugs is to breed, lay eggs for the next generation, and die.  Males live only 2-3 days, while females last about a week.  Adult lovebugs may feed on nectar and pollen, but they primarily subsist on food ingested while they were larvae.  At night they perch on low vegetation and do not become active until midmorning.  Swarms occur twice a year, in April-May and again in August-September, and last about 30 days.  They reach their peak density between 10:00 AM and 4:00 PM.  As soon as the females emerge, mating occurs, and the genitalia of the male and female lock together so that the larger female tows the smaller male behind her when she flies.  Copulation lasts about 12 hours and the male dies shortly after mating.  This locked together male-female pair is why they are called ‘lovebugs’. 
Lovebugs are most abundant in moist, grass-covered, open sunny areas such as pastures and the shoulders of highways with lots of decaying thatch.  The female lays up to 600 eggs on the decaying material.  Thousands of larvae have been found under cow pies in pastures.  The larvae live for months in and under the decaying litter, which they digest and recycle as organic compounds that feed the plants and improve the soil.  Larvae may be particularly abundant in rich sod.  The use of sod to roll out new lawns and to carpet the bare shoulders of new highways sped up the spread of lovebugs into new areas. 
Lovebug swarms are particularly dense along highways and roadways with humid grassy shoulders.  In addition, lovebugs are attracted to the aldehydes produced when ultraviolet light in sunlight breaks down the exhaust fumes of automobiles and tractor trailers.  They also are attracted to the heat radiating from the pavement and the heat and vibrations of the engines.  Lovebugs flying over the highways get squashed against the windshields, radiators, headlights, grills, and fronts of vehicles speeding through the aerial swarms.  In dense swarms, so many lovebugs get squashed on the windshield that the driver’s vision is quickly obscured.  They also can plug up the radiator fins and overheat the engine. 
Minced lovebug tissue is slightly acidic, but bacterial action will make it more acidic if it is left in place.  That acid can damage the car’s finish.  Squashed lovebugs are most easily scrubbed off while they are fresh and moist.  Once dried, they are more difficult to remove.  A little detergent helps.  But getting dried lovebugs out of clogged radiators may require the use of a pressure washer. 
Seasonal headache though they are, lovebugs are not all bad.  They do not bite or sting.  They are not poisonous.  They do not transmit diseases.  Their larvae help recycle organic material, and the carcasses of the billions of lovebugs that die each season contribute more nutrients to the soil.  Occasionally lovebugs are eaten by armadillos, birds, spiders, beetles, earwigs, and centipedes.  But none of these predators gorge themselves on lovebugs, apparently because they do not taste good.  The benefits lovebugs provide do not outweigh the nuisance, scourge, or plague represented by a cloud of them on the highway. 
When you get really, really fed up with lovebugs, remember it is your fault that they are here.  Well, not your fault personally; they are your fault collectively as a motorist.  Lovebugs would have migrated here from Texas anyway, but their abundance is a reflection of the super habitat we provide.  The myriad state and federal highways that were built to accommodate the vehicles we love and need not only eased transportation, they also replaced wooded areas and moist natural habitats with the open grassy areas preferred by lovebugs.  And heat from the pavement attracts them to the highways as does the breakdown products of the exhaust fumes from your car. 
You can avoid lovebugs by driving at night when they are resting on vegetation.  If you have to drive during the day, confine your driving to roads through heavily developed urban areas lacking large grassy plots.  Put aprons or bug screens on the front of your car to catch lovebugs before they plug up your radiator.  Use deflector shields to blow the lovebugs up and over the windshield.  And wash your car before the splattered lovebugs dry. 
If that will not do, if you simply cannot tolerate them any more, you can always go on a lovebug killing spree.  The easiest way to do that is to race up and down the highway in the heat of the day and squash them on your windshield.

Prof. F. Wayne King is Emeritus Curator at the Florida Museum of Natural History – kaiman@flmnh.ufl.edu