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Family CEstridae— The Bot Flies 



Flies of moderate to large size, thick set and for the most part more 

 or less pilose, the squamae large. 



Head large, the lower part more or less swollen; mouth opening 

 small, the mouth parts reduced in size, very small. Front broad in 

 both sexes, widening anteriorly in the male; ocelli present. Antenna; 

 short, composed of three segments, decumbent and partly sunken in 

 the facial depression or antennal grooves; arista bare. Eyes bare, rather 

 small. Thorax robust, with transverse suture; hypopleura bearing dense, 

 long hair. Abdomen short, conical or but little elongate; genitalia 

 hidden. Squama large. Wing venation as in the Tachinidae, the first 

 vein ending beyond the middle of the wing, the auxiliary vein long 

 and ending in the costa; fourth vein ending before the apex of the 

 wing, close to the third; both basal cells present, the second basal and 

 anal cell short. 



The CEstrids are not common in collections and good series of all 

 but a very few species are unusual. The adults are remarkably good 

 fliers, are excellent hoverers and extremely difficult to catch as well as 

 being rarely encountered. Some collectors have had success in locating 

 larva; and pupae in pastures, and rearing the adults. Otherwise one 

 usually runs across tlicm only by accident. 



In some cases the eggs are laid on the hind legs, the larv£e working 

 their way under the skin and through the muscles until they reach the 

 back, where they make an opening through wliicli to breath. The larva? 

 of some species live in the nasal sinuses and, in sheep, are responsible 

 for '' staggers". The exact means by which some of the species reach 

 their feeding places is not known, and, in fact, relatively little is known 

 about most species which have been described. 



In America the larvae of (Estrus ovis have been formed in the eye of 

 man. Normally the living larvae are deposited in the nostrils or eyes 

 of sheep, the fly dashing in and depositing a maggot. The larvae work 

 their way to the nasal sinuses and mature the following spring when 

 they either drop out or are ejecting during sneezing. In man they have 

 been found only in the eye, larviposition probably having taken ])lace 

 as described for sheep. However, there are no records of the victim 

 having been aware of the attack so it is possible that the larva was 

 deposited while the victim was sleeping. 



