Tour de Fly

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Published on: May. 2, 2003

Last revision: Nov. 15, 2010

narcissus bulb fly, Merodon equestris, is another convincing bee impostor. Its larva is unusual in being an occasional pest of daffodils.

In addition to impersonating bees, some of the fuzzy bee flies (Bombyliidae) parasitize them. A female Bombylius major hovers over the burrow of a solitary bee, and lobs eggs down the tunnel. The larvae that hatch crawl into the cells of their host, and feast on the pollen and nectar stored for the bee's offspring. Other bee flies are parasites of solitary wasps, tiger beetles or other insects. Several species have long beaks through which they sip flower nectar.

The bumblebee disguise of Laphria robber flies (family Asilidae) can even fool scientists who know better. Look for Laphria at rest on foliage, logs, and tree trunks in sun-splotched woodlands. They cock their heads as other insects pass overhead. When suitable prey presents itself, the fly dashes out, grabs its victim and returns to its perch to feed. A sharp, stout beak administers the kiss of death.

Robber flies of other types are more streamlined. Large Promachus species buzz loudly as they fly short distances from perch to perch. These and similar varieties, like Efferia, Proctacanthus, Asilus and Diogmites, are most abundant in open fields, glades and prairies, and along riverbanks and forest edges. They can kill large beetles and grasshoppers, and even cicadas. The habits of the larvae remain a mystery for most species, but some are external parasites of beetle larvae.

Horse flies and deer flies

Many of Missouri's forty-plus species of horse and deer flies have dazzling striped or spotted eyes. Horse flies (genus Tabanus) can be huge, while deer flies (Chrysops) are smaller, with dark spots or bands on clear wings. The blood-feeding females slice, dice and slurp with blade-like mouthparts and a sponge-like pad similar to a house fly's. In livestock, blood continues to flow after the flies have departed. The open wounds invite infection and provide sites for screwworms and other parasitic flies to lay their eggs. Bites to humans can result, rarely, in severe allergic reactions, and our sensitivity increases with each bite.

Female tabanids are attracted to dark, moving objects and shiny surfaces. They often chase cars and frequently wind up as roadkill. Males, with wrap around eyes, seek only nectar and females. They sometimes swarm above treetops and man-made structures, the better to attract the fairer sex.

Another biter is the

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