The Gnat. 593 
larvse, which the eggs contain, escape into the water in 
which they swim about with vigorous jerking move- 
ments. They are compelled to visit the surface to take 
in a supply of air, and for this purpose the tail is fur- 
nished with a short tube, surrounded at its extremity with 
a star of bristles, which, when spread out, prevent the 
water from flowing into the air tube. The change to 
the pupa state is a curious one. In this condition the 
insect exhibits a rather slender body with a bulky an- 
terior extremity, in which the head, wings, and limbs are 
enclosed ; the tail is furnished with a pair of leaves or 
membranous plates, the matting tube has vanished from 
this part and in place of it we find two tubes situated on 
the sides of the thorax : having passed about ten days in 
this state, its increase being at an end, it keeps longer 
near the surface, and at last the outer skin bursts, and 
the winged insect, standing upon the exuvice it is going 
to leave behind, smooths its new-born wings, springs 
into the air, and begins its depredations. The fecundity 
of the Gnat is so remarkable, that in the course of one 
summer they might increase to the amazing number of 
five or six hundred thousands, if Providence had not 
ordered that they should become the prey of birds, who 
by this means prevent their multiplying more than they 
generally do. These insects are very annoying from their 
blood-sucking propensities ; and as the sucker is horny 
at the tip, it inflicts a severe wound, into which the insect 
emits a small quantity of poison, which occasions the pain 
and inflammation always felt from a Gnat bite. 
2Q 
