448 INSECTS INJURIOUS TO VEGETATION. 



feather. The wings are fihiiy, 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 lat- 

 ter, in many females, ends with a tapering, retractile tube, 

 wherewith the eggs are deposited. The legs are six in num- 

 ber, 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 prevent 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 sometimes are 

 mistaken for worms. They vary a good deal in their forms, 

 structure, habits, and transformations, so that it is somewhat 

 difficult to give any general description of them. Their 

 breathing holes are usually situated near the extremities of the 

 body. Aquatic maggots often have a tubular tail, through 

 which they breathe, and the orifice of this tube is sometimes 

 surrounded with beautiful feather-formed appendages. The 

 larvEB or maggots of the gnats, and of nearly all those flies 

 which have four or sLx bristles in the proboscis, have a distinct 



