LARVjE of gnats and flies. 
563 
insects. The head is large, and fastened to the thorax by a 
very slender neck. The eyes, especially in the males, are 
large, and occupy the whole of the sides of the head. The 
antennae, in gnats and mosquitos, are rather long, slender, 
and many-jointed ; in flies, they are short, consisting of only 
two or three thick joints, the last of which often bears a 
little bristle or delicate feather. The wings are filmy, like 
those of Hymenopterous insects, hut usually have a greater 
number of veins in them. Just behind the wing-joints there 
are two little, convex scales, which open and shut with the 
motion of the wings ; they are called the winglets. The 
two balancers or poisers are short threads, knobbed at the 
end, and placed on each side of the hindmost part of the 
thorax, immediately behind the winglets. The thorax is 
often the thickest and hardest part of the body ; to it the 
hind body is more or less closely united, and the latter, in 
many females, ends with a tapering, retractile tube, where- 
with the eggs are deposited. The legs are six in number, 
and each of the feet is provided with two claws, and two 
or three little cushions or skinny palms, by the help whereof 
the insects can walk on the smoothest surfaces, and on the 
ceilings of rooms, with the back downwards, as easily as 
when upright ; for the palms act like suckers, and thus pre- 
vent them from falling. 
Mosquitos and gnats are active both by day and night, 
but flies take wing only during the day. The life of these 
insects, even from the time when they are first hatched, is 
generally very short, seldom lasting more than a few weeks ; 
but of some kinds several broods are produced in the course 
of a single summer, and often in the greatest profusion. In 
certain countries and seasons they multiply so fast, and 
appear in such immense swarms, as to become a serious 
annoyance both to man and beast. 
The young insects, hatched from the eggs of gnats and 
of flies, are fleshy larvae, usually of a whitish color, and 
without legs. They are commonly called maggots, and 
