t 417 ] 



THE OESTRI, or GAD-FLIES*. 



THE mouth in the Oestri is merely a simple aper- 

 ture. They have two feelers, but no beak. The 

 antennas are short, and consist of three articulations, 

 the last of which is nearly globular, and furnished 

 with a bristle on the fore part : they are placed in 

 two hollows on the front of the head. The face is 

 broad, depressed, vesicular and glaucous, and has 

 been thought to bear some distant resemblance to 

 that of the Ape tribe. 



The larvae are without feet, short, thick, soft and 

 annulate, and are often furnished with small hooks« 

 These lie hid in the bodies of cattle, where they are 

 nourished the whole winter. The perfect insects 

 are to be met with in the summer in most places 

 where horses, cows, or sheep are grazing. Some of 

 them lay their eggs under the skin of cows or oxen, 

 which they pierce for that purpose ; others, for the 

 same end, are conveyed into the intestines of horses: 

 and others again deposit them in the nostrils of sheep. 

 In these different habitations the respective larva? 

 reside till full grown, when they let themselves fall 



T 



* The Linnean order Diptera commences here. 



vol. in. E e 



