866 A N JNTROD UCTION TO ENTOMOLOG Y 



The chin-fly or the throat-bot, Gastrophilns nasalis. — This species 

 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 sometimes the eggs are laid upon the flanks 

 or forelegs of the host. The manner in which the larvae reach the 

 mouth of the horse has not been definitely determined; but having 

 reached the mouth they are carried down the alimentary canal. In 

 some cases the larva; attach themselves to the pharynx,^ and as this 

 is the only species that is known to do this, the larva is known as 

 the throat-bot. But this species is sometimes found in the stomach, 

 and it attaches by preference in the duodenum. When the larvae 

 are matured they pass out from the horse and burrow in the manure 

 or soil to transform. 



This species is widely distributed in the United States and Canada. 



The red-tailed bot-fly or the nose-fly, Gastrophilus hmnorrhoidalis. 

 —The adult fly 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. The larv^ae of this species 

 attach themselves during their early stages within the stomach ; but 

 later loosen themselves and reattach in the rectum, from which they 

 gradually move to the anus, where they remain for a short time before 

 dropping to the ground to transform. 



This species is found in the North-Central and Northern Rocky 

 Mountain States and in the western provinces of Canada. 



Family CESTRID^ 

 Bot-Flies {except Gastrophilus) 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 venation of the wings dift'ers from 

 that of the preceding family in that vein Mi -1-2 is bent so that cell R5 

 is much narrowed or closed at the margin of the wing. 



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 ; 

 and closely allied ocstrids are parasitic, in a similar manner, upon 

 closely allied mammals. 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 

 very common in the South. 



