CHAPTER VI I. 
DIPTERA. 
Gnats and Flies. — Maggots, and their Transformations. — Gall-Gnats. 
Hessian Fly. — Wheat-Fly. — Remarks upon and Descriptions of some 
other Dipterous Insects. — Radisii-Fly. — Two-winged Gall-Flies, and 
Fruit-Flies. — Conclusion. 
NDER 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 winged 
