COLEOPTERA. 477 



means of the two bristles situated at the extremity of the abdomen 

 (Fig. 472). After having drawn this after her for some time, she 

 leaves it to itself in calm water. At the end of a fortnight there 

 come out from it little brown larvae, very active, which ascend the 

 water plants. These larvae are at the same time herbivorous and 

 carnivorous. They live on plants and small molluscs, which they 

 seize from underneath, and whose shell they break by pressing them 

 against their back, to extract from it the animal. If attacked, they 

 emit a black liquid, which discolours the water, and enables them to 

 escape. At the end of two months the larva comes out of the water, 



Fig. 472. Bristles at the extremity of the Fig. 473. Pupa of the Hydrophilus. 



abdomen of the Hydrophilus. 



and burrows into the ground to undergo its metamorphosis into a 

 pupa (Fig. 473), which becomes a perfect insect a month afterwards. 

 The latter gets its colour little by little, and comes out of the ground 

 at the end of twelve days. According to M. Dumeril, the intestine 

 of the larva grows gradually longer and longer, and its diet becomes 

 that of herbs, the adult preferring vegetable food to animal matter. 

 It is at the end of summer that the Hydrophilus piceus becomes 

 perfect, and it passes the winter in a state of torpor at the bottom of 

 the water. The females lay in the month of April. A small species, 

 Hydrous caraboides, is commoner than the large one; its body is 

 more rounded behind. 



We are now going to consider a series of aquatic and carnivorous 

 insects ; the Dytisci, Water Beetles, the Cybistcrs, and the Gyrinida, 



