ORDER VII. 



TWO-WINGED INSECTS, OK FLIES (DIPTERA). 



THE insects of this order, as their Greek name imports, 

 are creatures with two wings, which we commonly call 

 flies. They are generally small, and we find among them 

 some so diminutive that they can be seen only with a mag- 

 nifying glass. Their bodies are divided into a head, tho- 

 rax, and hind body or abdomen, which are connected to- 

 gether by a thin filament. The head consists of two large 

 eyes, with an addition in some species of three small ones, 

 and two short antennas, very near together; below these 

 are found, in some species, a soft proboscis, as in the house- 

 fly ; in others a hard, pointed sucking-tube, as in the mos- 

 quito ; and in others simply a mouth. On the under side 

 of the thorax arc fastened three pair of feet, and on the 

 opposite side one pair of thin, transparent wings, by the 

 vibration of which they produce a humming sound when 

 flying. The hind body consists of ten ringlets. 



These insects are for the most part oviparous, only a few 

 species being viviparous. Their maggots are white, of a 

 spindle form, and without feet, but some of them have mi- 

 nute fleshy warts which answer the purpose of feet, and 

 upon which they are able to move ; they have two respira- 

 tory organs on the neck, and two on the hind body. Many 

 of these larvae live in the water, but the greatest part of 

 them live in dirt, dung-hills, cheese, spoiled meat, fruits, 

 etc. After a time the skin of these mnggots becomes hard 

 and brown, and thus they are transformed into a pupa, 

 which in many species has the form of a barrel, from which 

 afterward the perfect fly issues. 



