286 SUPPLEMENT ON THE CARNIVOROUS FAMILY 



of perfect quiescence, but the moment they are approached, 

 they put themselves in motion, and escape by swimming or 

 sinking into the water with the greatest quickness. Some- 

 times they remain at the bottom of the water, and keep 

 themselves hooked to some aquatic plant ; for, as they are 

 lighter than the water, they come to the surface if they do 

 not keep themselves fastened to something, and not stir their 

 feet. The upper part of their body remains entirely dry 

 when they are at the surface of the water ; but when they 

 dive, a sort of little silvery ball remains attached to their 

 back, which produces a very pretty effect. A disagreeable 

 odour exhales from their bodies when they are touched, 

 which it is very difficult to get rid of. They are found in 

 the waters from the time that the frosts give over, in spring, 

 until it is far advanced in the autumn. 



The females lay their eggs on the leaves of aquatic plants. 

 Degeer kept some in a decanter filled with water, which 

 deposited their eggs on the sides of the glass, one after the 

 other. In about eight days the young hexapod larvae, very 

 small, issued forth from the eggs, and swam at first in the 

 Avater ; they also walked against the sides of the glass. 

 Roesel was acquainted with these larvae, but was not able to 

 bring them up to their full size. This also happened to 

 Degeer, who never could preserve them alive for any length 

 of time. But M. Modeer, who has given a history of these 

 little insects in the memoirs of the Royal Academy of 

 Sciences of Sweden, has had these larvae in their full size, 

 and has given a description of them, which agrees in all 

 points with tliat of the young larvae. This gentleman, how- 

 ever, has not informed us how these larvae came into his 

 possession, whether he hit upon the means of rearing them 

 from their birth, or gained possession of them when they 

 were fully formed in the waters. He also speaks of their 

 transformations which took place out of the water. About 



