LARVAE 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, but 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 fist, 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, aiul 

 without legs. They are commonly called maggots, and 



