282 SUPPLEMENT ON THE CARNIVOROUS FAMILY 



almost above the water. They afterwards raise the elytra a 

 little, or lower the end of the abdomen. When the insect 

 wishes to return to the bottom of the water it brings the 

 belly and the elytra promptly together, and stops the vacuum 

 which was between them, so that the water can no longer 

 penetrate there. 



The dytisci live in all kinds of fresh waters, in rivers, lakes, 

 but more especially in marshes and ponds. They swim with 

 very great celerity. It is usually at the approach of night 

 that they issue from the water to fly and transport themselves 

 from one pond or marsh to another. Accordingly these in- 

 sects, and many others, which, like them, are amphibious, are 

 found in the smallest pieces of water, even in those which are 

 formed by the descent of rain. They make a humming 

 noise in flying, like the scarabei. In coupling, the male 

 employs the two remarkable palettes which are presented 

 by the anterior tarsi, to hold himself fixed to the female. 

 The inferior surface of these palettes presents, in large 

 spaces, a great number of small concave pieces, in the 

 form of the calix of flowers, or little cups, and some of 

 which, particularly the largest, have, at their bottom, a little 

 elevation. We may again consider these calices as species of 

 cupping-glasses or suckers. The mode in which the females 

 deposit their eggs is unknown. 



The skin which covers the larvas of the dytisci is generally 

 scaly, and something like the plates of a tortoise. The two 

 last rings of the body are furnished towards the sides with 

 a sort of fringe, which being placed on a ridge, or a line 

 somewhat elevated, seem to be formed for swimming. 

 When the larva suddenly wishes to change place in the 

 water, or fly the approach of some large insects which might 

 devour it, it gives a prompt and vermicular movement to its 

 body, striking the water with its tail, the fringe of which 

 then becomes very useful to it, since the tail is thereby 



