178 DIPTERA. 



are in like manner bounded with yellow-coloured zones. 

 They are fortunately not very common, the time of their 

 appearance, and the disti'icts they inhabit, being limited. 

 There are several species of these dreaded flies, each of 

 which passes its larva condition as a parasite, living at 

 the expense of some particular quadruped. The horse, 

 the ox, the ass, the reindeer, the stag, the antelope, the 

 camel, the sheep, and the hare are, however, the only 

 animals certainly known to be subject to their attacks, and 

 these all seem to be inspired with a special dread of their 



Fig. 138.— gadflies. 



insect tormentors. Of these larvae, some are dej)0sited 

 under the skin of the backs of cows by means of a pecu- 

 liarly-constructed ovijDositor, with which the females are 

 provided. The eggs of others are simj^ly glued to the 

 skin in the vicinity of the nose of sheej) and deer, whence 

 the maggots creep into the nostrils of the poor animal, 

 where they reside. The larvae of a third kind are only 

 met with in the stomach of the horse, where alone they 

 find a suitable residence. In this situation they are called 

 hots ; the manner in which they are introduced into such a 

 strange locality is very ingenious. The fly, when laying 

 her eggs, may be seen balancing herself in the air and 

 glueing them to such parts as the horse is in the habit of 

 licking with his tongue, and thus he is made unconsciously 

 to introduce them into their proper nursery. These larvae 

 are footless, of an oval shape, and banded with circles of 

 hooks, whereby they attach themselves. When mature, 

 they are expelled, and falling to the ground, bury them- 

 selves in the earth, where their last change is accom- 

 plished. 



The Flesh Flies (Musca) are too well known to need 

 description. These creatures dej^osit their progeny in 

 tainted or in putrefying flesh, and notwithstanding the 



