BOT FLY

any member of several small insect families of the order Diptera. The adults are beelike in appearance, hairy but without bristles; the larvae are parasitic on mammals. Horse bot flies (family Gasterophilidae) include species of Gasterophilus, a serious horse pest. The adult horse fly, often known as a gad fly, deposits between about 400 and 500 eggs (nits) on the horse's forelegs, nose, lips, and body. The larvae remain in the eggs until the horse licks itself. With the stimulus of moisture and friction the larvae emerge, are ingested, and attach themselves to the lining of the horse's stomach or intestine, obtaining all their nourishment and oxygen from the horse's alimentary canal. The larvae mature after 8 to 11 months and are eliminated with excrement. Warble flies (Hypoderma lineatum and H. bovis) greatly disturb cattle. Young larvae penetrate the skin, migrate through the body for several months, then come to rest beneath the skin of the animal's back; here each larva causes a characteristic lump, or warble, from which a cattle grub emerges. The grub becomes a pupa and then a fly to deposit more larvae. In the family Oestridae are the North American and European deer nose bot flies (Cephenomyia); perhaps the swiftest flying insects, they can fly approximately 50 miles per hour (80 km per hour). Another important nose fly (family Oestridae) is the sheep bot fly (Oestrus ovis). Active larvae, deposited in the nostrils of the sheep, often cause a nervous condition called blind staggers. The important rodent bot flies (family Cuterebridae) are Cuterebra cuniculi, which infects rabbits, and C. emasculator, which attacks the scrotum of squirrels, sometimes emasculating them. The human bot fly (Dermatobia hominis) of the family Cuterebridae attacks livestock, deer, and humans. The female attaches her eggs to mosquitoes, stable flies, and other insects that carry the eggs to the actual host. Body warmth causes the eggs to hatch, and the tiny larvae penetrate the skin. In tropical America Dermatobia is responsible for loss of beef and hides.