3 2o THE STUDY OF INSECTS 



female (Fig. 563) has the end of the abdomen elongate and bent forward 

 under the body. The wings are transparent with dark spots, those near 

 the center form an irregular, transverse band. This fly is 

 most often seen flying about horses, which have an instinc- 

 tive fear of it. The eggs are laid on different parts of the host, 

 but preferably on the long hairs investing the inside of the 

 fore legs. The eggs rarely hatch when left untouched; but 

 the horse by scratching the fore legs with the teeth removes 

 fig. 563. t j ie sma u ca p f th e egg-shell and inadvertently takes the larva 

 into its mouth. The larvae thus taken into the mouth are carried with 

 the food or water to the stomach. When the larvae reach the stomach 

 they fasten themselves to the inner coat of it, and remain there until 

 full-grown. Then they pass from the animal with the dung, and crawl 

 into some protected place, where they transform within a puparium. 



The chin-fly or the throat-bot, Gasterophilus veterinus, is smaller than 

 the common bot-fly and the wings are not marked with dark spots as in 

 that species. The female usually deposits its eggs upon hairs under the 

 jaws, and for this reason is commonly known as the chin-fly; but some- 

 times the eggs are laid upon the flanks or fore legs of the host. 



The red-tailed bot-fly or the nose-fly, Gasterophilus hcemorrhoidalis , is 

 easily distinguished by the bright orange-red tip of the abdomen. The 

 wings are unspotted as in the chin-fly but differ from those of both of 

 the preceding species in that the cross-vein m-cu is much farther from 

 the base of the wing than is cross-vein r-m. The female oviposits on the 

 lips of the horse; the flight of the fly about the nose of the horse when 

 attempting to oviposit on its lips, suggested the common name, the nose- 



fly. 



Family CEstrid^; 

 Bot-flies (except Gasterophilus) and Warble-flies 



This family includes flies that are large or of medium size; most of 

 the species resemble bees in appearance; some, the honey-bee, others, 

 bumblebees. The mouth-opening is small, and the mouth-parts are 

 usually vestigial. 



The larvae are parasitic upon mammals; some develop in tumors 

 under the skin and others, in the pharyngeal and nasal cavities of their 

 hosts. As a rule each species infests a single species of mammal. In 

 addition to the species that infest our domestic animals, other species 

 infest rabbits, squirrels, deer, and reindeer. One that lives beneath the 

 skin of the neck of rabbits is common. 



The sheep bot-fly, CEstrus ovis.- — This species is viviparous; the 

 female fly deposits larvae, which have hatched within her body, in the 

 nostrils of sheep. The larvae pass up into the frontal sinuses and into the 

 horns when they are present. Here they feed upon the mucus. They 

 are very injurious to sheep, causing vertigo or the condition known as 

 "staggers." When full-grown they pass out through the nostrils and 

 undergo their transformations beneath the surface of the ground. 



The heel-fly, Hypod&rma lineatutn. — The adult fly is \ of an inch in 

 length; the anterior part of the thorax is black and shining; the alulae 

 are uniformly white; and the tail end of the abdomen is reddish-orange 



