BOT-FLY, name common to several dip terous insects of the family Oestrida which are parasitic in their early stages upon or within certain domestic or wild animals. The body is stout, hairy, like the bumblebees, and they are easily recognized by having the opening of the mouth very small, with rudimental oral organs. The middle part of the face is exceedingly narrow and the minute antenna are inserted in rounded pits. The eggs hatch very soon after laying, and Riley thought, from the tes timony of three independent witnesses, that the sheep bot-fly is viviparous, the larva hatch ing within the body of the parent, who deposits in the nostrils of the sheep the perfectly formed and living grub.
The larva are, in general, thick, fleshy, foot less grubs, consisting of 11 segments, exclusive of the head, which are seined and tuberculated, the former in rows, which enable them to move about readily when living under the skin or in the frontal sinus and thus greatly irritate the animals on which they live. The stigmata are placed in a scaly plate on the thickened posterior end of the body. The mouth of the cutaneous larva consists simply of fleshy tubercles, while in those species that live in the stomach and frontal sinuses of their hosts, it is provided with horny hooks. While in this state they moult twice and then attain their full size. They feed on the purulent matter originating from the irritation produced by the movements of their bodies. Just before assuming the pupa state, the larva leaves its peculiar habitat, descends into the ground and there becomes a coarctate pupa. (See PUPA).
Besides the horse bot-fly (q.v.), the ox bot fly (q.v.) and the sheep bot-fly (q.v.), there is included in the genus Dermatobia the aver macaque" of Cayenne and Mexico, which is found beneath the skin of man in tropical America. It is disputed whether it be a true
indigenous "Estrus or one that orig inally attacked the monkey, dog or other mam mal. In Cayenne the species attacking man is called the aver macaque," in eastern Brazil (Para) aura," in Costa Rica atorcel," in Co lombia egusano peludo" or umuche." The over moyocuil* (D. noxialis) lives on the dog, sheep, cattle and man, and is found in Mexico and New Granada. The larvae are long, cylindrical, S-shaped, differing greatly in form from others of this family. The flies are closely allied to those of the preceding genus.
Leidy states that several specimens of the larva of a bot-fly were obtained in Honduras (by Le Conte). They were usually found be neath the skin of various parts of the body and the eggs were suspected to have been intro duced while the persons were bathing. The men were not aware of the circumstance, and the presence of the larva gave them comparatively little uneasiness. According to Krefft, a species of Batrachomyia is parasitic upon four species of Australian frogs. The larvae are found be tween the skin and the flesh behind the tympa num. When they quit the frog the latter dies. The change to the pupa state is usually effected on the lower surface of a piece of rock in some damp locality. The perfect insect emerges in 32 days. Consult Packard, 'Guide to Study of Insects' (1889); Brauer, (Monographie der Oestriden' (Vienna 1863); Osborn, 'Insects Affecting Domestic Animals' (Bulletin No. 5, N. S. Division of Entomology, United States Department of Agriculture, Washington 1896, which also contains an extensive bibliography of the Oestrida%)