THE GNAT. 1S3 



resting history. Before they turn to flying 

 insects, they have been in some measure 

 fishes under two different forms. From the 

 beginning of May, till winter, small grubs 

 may be seen with their heads downward, 

 and their hinder parts on the surface of the 

 water, from which part arises sideways, a 

 kind of vent-hole, or small hollow tube, like 

 a funnel, and this is the organ of respira- 

 tion. The head is armed with hooks, that 

 serve to seize on insects, and bits of grass, 

 on which it feeds. On the sides are placed 

 four small fins, by the help of which the 

 insect swims about, and dives to the bottom. 

 These larvae retain their form during a 

 fortnight or three weeks, after which period 

 they turn to chrysalids. All the parts of 

 the winged insect are distinguishable through 

 the outward robe that shrouds them. The 

 chrysalids are rolled up into spirals. The 

 situation and shape of the windpipe is then 

 altered; it consists of two tubes near the 

 •head, which occupy the place of the stig- 

 mata, through which the winged insect is 

 one day to breathe. 



These chrysalids constantly on the sur- 



