DIPTERA. BRACHYCEEA. 371 



The horse is subject to the attacks of four species of 

 Botfly, of which, however, only one is common. This 

 insect, Gasterophilus equi, deposits its eggs, not in their 

 final place of rest, which, being the stomach of the horse, 

 is inaccessible to the Fly, but on the surface of its body, 

 within reach of the tongue. The animal, by licking itself 

 and swallowing them, transfers the unwelcome little 

 stranger into its own inside, where it grows and prospers, 

 till, as in the former cases, it detaches itself, and dis- 

 charged by the horse, falls to the ground, and undergoes 

 the final changes. This Fly is sometimes as much as two- 

 thirds of an inch in length. It differs from both the 

 preceding in the very small size of the winglets. The 

 legs are of moderate size and strength. It is somewhat 

 rust-coloured, black at the tip of the abdomen. There 

 are varieties, differing in colour. 



Another species of Gasterophilus lays its eggs on the 

 lip of the horse. 



Besides the above-mentioned Flies, there are some 

 rarer species infesting deer; and in other countries, 

 several more are known, one even selecting the rhino- 

 ceros as its host, while others have been known to 

 attack men. 



The third sub-section of the Proboscidea is HTPOCERA. 

 The antennse themselves differ little in this from some 

 of the Brachycera, but are differently placed, being very 

 near the mouth, instead of as in the Brachycera, between 

 the eyes. 



This division consists of but one genus, Phora, con- 

 taining only a few species of minute Flies, ranging in 

 size from one twenty -fourth of an inch to one-sixth of 

 an inch. Some of these are exceedingly common, and 

 haunt the window-panes throughout the year. They 

 B B 2 



