CHAPTEE VII. 



DIPTERA. 



Gnats and Flies. — Maggots, and their Transformations. — Gall-Gnats. 

 Hessian Fly. — Wheat-Fly. — Remarks upon and Descriptions of some 

 other Dipterous Insects. — Radish-Fly. — Two-winged Gall-Flies, and 

 Fruit-Flies. — Conclusion. 



UNDER the name of Diptera, signifying two-winged, 

 are included all the insects that have only two wings, 

 and are provided with two little knobbed threads in the 

 place of hind wings, and a mouth formed for sucking or 

 lapping. 



Various kinds of gnats and of flies are therefore the in- 

 sects belonging to this order. The proboscis or sucker, 

 wherewith they take their food, is placed under the head, 

 and sometimes can be drawn up and concealed, partly or 

 wholly, within the cavity of the mouth. It consists of a 

 long gutter, usually ending with two fleshy lips, and enclos- 

 ing, in the channel on its upper side, several fine bristles, 

 from two to six in number, which are sometimes as sharp 

 as needles, and are then capable of inflicting severe punc- 

 tures. These piercing bristles really take the place of the 

 jaws of biting insects, and hence the wounds made there- 

 with, by gnats and mosquitos, are very properly called bites. 

 The saliva of these insects, flowing into the wounds, renders 

 them more painful, and is the cause of the inflammation and 

 itching that follow. The grooved sheath of the proboscis is 

 usually very large and fleshy in the flies that only lap or sip 

 their food. Two small, jointed feelers are commonly found 

 attached to the base of the proboscis. 



Gnats and flies have softer bodies than most other winded 



