318 NATURALIST'S CABINET. 



Biliereut changes. 



hooks, that serve to seize on insects and bits of 

 grass on which they feed; and on their sides are 

 four small fins, by the help of which they 

 swim and crawl along. These larvae retain 

 their form during a fortnight or three weeks, 

 after which they turn into chrysalids; and all 

 the parts of the winged insect are now distin- 

 guishable through their thin exterior covering. 

 The situation and shape of their respiratory tube 

 is also altered: this is now divided into two parts, 

 and is placed near the head. The chrysalids ab- 

 stain from eating, and reside almost constantly 

 at the surface of the water; but, on the least mo- 

 tion, they may be seen to unroll themselves from 

 their spiral position, and, by means of little pad- 

 dles on their hinder part, to plunge to the bot- 

 tom. In the course of a few days they are trans- 

 formed into perfect gnats. The chrysalids swell 

 at the head, and the rlies burst from their 

 inclosure. If at the instant of the change a 

 brt-eze springs up, it proves to them a dreadful 

 hurricane, as the water gets into their case, from 

 which they are not yet perfectly loosened ; this 

 immediately sinks, and they are drowned. 



The female deposits her eggs on the surface 

 of the water, and surrounds them with a kind of 

 unctuous matter, which prevents them from sink- 

 ing : and she at the same time fastens them with 

 a thread to the bottom to prevent them from 

 floating away, at the mercy of every breeze, from 

 a place the warmth of which is proper for. their/ 



