35 



Worma]s, or Warbles), reside in tumours beneath the skin of the animal attacked, for ex- 

 ample the ox bot-fly; Cervical, when the grubs burrow into the maxillary and frontal si- 

 nuses, through the nostrils, as is the case with the sheep breeze-fly ; or gastric, when the 

 grubs, called in this case bots, are introduced into the stomach, like those of the horse 

 gad-fly. 



We gather from various sources that the horse, sheep, ox, ass, reindeer, rhinoceros, 

 stag, antelope, camel, hare, rabbit, rat and mouse are subject to the attacks of these in- 

 sects, and it is mentioned as a singular anomaly that some of the genera which contain 

 the largest species among them, inhabit the smallest animals. 



These insects whose habits are so formidable, and whose economy is so extraordinary, 

 have the appearance of large hairy flies, the hairs being often coloured in transverse bands. 



Having thus learned something of the general history of the breeze-flies, let us now 

 take them in order and more minutely examine the three several species we have alluded 

 to. 



1. — The Horse Breeze-Fly {(Estrus [gasterophUus] equi, Fab). 



Fi- 25. Male. joly thus dcscribcs this fly. The head is large and obtuse, 



the face light yellow with whitish silky fur, the eyes blackish, theanten- 

 na3 ferruginous, the thorax grey, and the abdomen of a reddish yel- 

 low, with black spots. The wings are whitish, not diaphanous, with 

 a golden tint, and divided by a winding band of blackish colour ; the 

 feet are palish yellow. The body of the female, fig. 26, is long, tap- 

 ering and sharp pointed, while that of the male is round and obtuse. 



No quadruped is more infested by the breeze or bot-fly than the 

 horse. During the months of July and August when horses are gene- 

 rally turned out to grass, the (Estrus frequents the pastures for the purpose of laying its 

 eggs. We will refer here to Mr. Newman's description of extracts from Mr. Clark's mas- 

 terly essay. 



Fig. 26. Female. 



The female (Estrus in ap- | | posit the egg, she suddenly darts 



proaching the horse for the purpose ^ ) upon it, and leaves the egg ad- 



of depositing her eggs, carries her ^^^^^^Sfc^^^^ hering to the hair. She hardly 

 body nearly upright in the air, -^^' Ja fl ^ ^^^*^^ appears to settle, but merely 

 the protruded ovipositor being yjOMfV^ touches the hair with the egg 

 curved upwards and inwards. / 1*1 V held out on the projected point of 



Suspending herself for a few se- / W > abdomen or ovipositor as it is 



conds before the part of the 1 called, the egg adhering by means 



horse on which she intends to de- of the glutinous liquor with which 



it is covered. She then leaves the horse at a small distance, prepares a second egg, and 

 poising herself before the part deposits it in the same way : the liquor dries, and the egg 

 becomes firmly glued to the hair. This is repeated until four or five hundred eggs are 

 sometimes placed on one horse. The skin of the horse is usually thrown into a tremulous 

 motion on the touch of the insect, which merely arises from the very great irritability of 

 the skin and cutaneous muscles at this season of the year, occasioned by the heat and 

 continual teasing of the flies, till at length these muscles appear to act involuntarily on 

 the slightest touch of any body whatever. 



The fly does not deposit her eggs at random on the horse's body, but selects those 

 parts which are most likely to be nibbled by the horse. The inside of the knee is fre- 

 quently chosen, but all naturalists must have remarked how commonly the eggs of the 

 bot are deposited on that part of a horse's shoulder which he can never reach with his 

 mouth, and thus to a casual observer it would seem they must perish and fail in the object 

 for which their parent designed them. Now there is a provision of nature which exactly 

 counteracts this difliculty. When horses are together in a pasture and one of them feels 

 an irritation on any part of the neck or shoulder which he cannot reach with his mouth, 

 he will nibble another horse in the corresponding part of his neck and shoulder, and the 

 horse so nibbled will immediately perform the kmd oflice required, and begin nibbling 

 away in the part indicated, 



