FLESH-FLIES. 133 



jerking movements, commence their lives under a very different aspect. Their 

 larvae are provided with a breathing apparatus, which resembles the tail of a 

 rat, and which they are able to elongate or shorten, so as always to keep its 

 tubular extremity above the surface of the filthy stuff in which these creatures 

 live. They are often found in great numbers in old tubs that contain stink- 

 ing rain-water 



The Gad-Flies (Oestrus] have much the appearance of humble-bees, and 

 the hairs that densely clothe their bodies are in like manner bounded with 

 yellow-coloured zones. They are fortunately not very common, the time of 

 their appearance and the districts 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 



FIG. 138. GAD-FLIES. 



the hare are, however, the cn'v animals certainly known to be subject to their 

 attacks, and these all seem to be inspired with a special dread of their tor- 

 mentors. Of these lame, some are deposited under the skin of the backs of 

 cows by means of a peculiarly constructed ovipositor with which the females 

 are provided. The eggs of others are simply glued to the skin in the vicinity 

 of the nose of sheep and deer, whence the maggots creep into the nostrils of 

 the poor animal, where they reside. The larvae of a third kind are only to be 

 met with in the stomach of the horse, where alone they find a suitable resi- 

 dence : in this situation they are called bots. The manner in which they are 

 introduced into such a strange locality is very ingenious. The fly, when lay- 

 ing 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, where- 

 by they attach themselves. When mature they are expelled, and, falling to 

 the ground, bury themselves in the earth, where their last change is accom- 

 plished. 



The Flesh-Flies (Mused) are too welt known to need description. These 

 creatures deposit their progeny in tainted or in putrefying flesh, and notwith- 

 standing the petty injury they inflict in our larders, they must be looked upon 

 as being among the most important agents employed in the police of Nature. 

 Death is everywhere abroad, but the earth is not permitted to be long defaced 

 by the presence of decay. No sooner does the carcase fall than these, 



"The swiftest of His winged messengers," 



are set to work, and speedily remove the offensive carrion. Linnaeus asserted 

 that three flesh-flies could devour a dead horse in less time than it would take 



