TWO-WINGED INSECTS. 293 
are divided into two sections—Land-bugs and Water- 
bugs. To the former section belong the Bedbugs be- 
fore referred to. Of the Water-bugs there are only two 
families—the Boat-flies and the Water Scorpions. The 
former are good swimmers, always swimming on the 
back. They can fly well, but rarely do it. 
499. The Diptera, or two-winged insects, constitute 
one of the most extensive orders, both in the number of 
species and in the number of individuals. None of them 
are large, and some are exceedingly small. For the most 
part they are dull in color. On the head are two very 
large compound eyes, and two short antenne near to- 
gether. In some there is a soft proboscis, as the com- 
mon House-fly ; in others, a hard, pointed, sucking tube, 
as in the Musquito; and in others still, simply a mouth. 
They have three pairs of feet, and two thin wings, which, 
in most cases, give out a humming sound in flying. 
Their larve are generally maggots, white, and having 
no feet, but instead thereof fleshy tubercles or warts, on 
which they crawl. Most of the larve live in dirt, or 
dung-hills, or spoiled meat, or cheese, etc. The meta- 
morphosis is complete, but in some cases very peculiar. 
500. The species of Flies are very numerous. There 
are about seventeen hundred known in Europe. The 
larvee of Flies, the maggots, generally live in some kind 
of filth; but the Flies themselves live, for the most part, 
on dainty food. The wing of a common Fly, examined 
under the microscope, is a beautiful object. Although to 
the naked eye it has a very plain appearance, it is cover- 
ed with little pointed projections of curious shape regu- 
larly arranged. 
501. The larvee found in cheese come from eggs depos- 
ited by a small Fly. From their great power in leaping 
they are called Cheese-hoppers. The manner in which 
the leap is performed is very singular, and is thus de- 
scribed by Carpenter: “*‘ When preparing to leap, it first 
raises itself upon its tail,in which position it is enabled 
