THE BOX FLY. 



77 



We now come to the Bot flies, which are among the most 



extraordinary, in their habits, of all insects. The history of the 



Bot flies is in brief thus. The adult two-winged fly lays its eggs 



on the exterior of the animal to be infested. They are conveyed 



into the interior of the host, where they hatch, and the worm or 



maggot lives by sucking in the purulent 



matter, caused by the irritation set up by 



its presence in its host ; or else the worm 



itself, after hatching, bores under the skin. 



When fully grown, it quits the body and 



finishes its transformations to the fly-state 



under ground. Many quadrupeds, from 



mice, squirrels, and rabbits, up to the ox, 



horse, and even the rhinoceros, sufl er from 



their attacks, while man himself is not 



exempt. The body of the adult fly is stout 



and hairy, and it is easily recognized by 



having the opening of the mouth very small, 



the mouth-parts being very rudimentary. 



The Iarva3 are, in general, thick, fleshy, 



footless grubs, consisting of eleven seg 

 ments, exclusive of the head, which are covered with rows of 



spines and tubercles, by which they move about within the body, 



thus irritating the animals 

 in which they take up their 

 abode. The breathing pores 

 (stigmata) open in a scaly 

 plate at the posterior end 

 of the body. The mouth- 

 parts (mandibles, etc.) of 

 the subcutaneous larvae con 

 sist of fleshy tubercles, while 

 in those species which live 

 in the stomachs and frontal 

 sinuses of their host, they 

 are armed with horny hooks. 

 The larvae attain their full 

 size after moulting twice. 



79. Human Bot Worm. 



80. Horse Bot Fly. 



Just before assuming the pupa state, the maggot leaves its pecu 

 liar dwelling place, descends into the ground and there becomes 

 a pupa, though retaining its larval skin, which serves as a pro 

 tection to it, whence it is called a &quot;pupariunu&quot; 



