I AQUATIC BEETLES 65 



powerful mandibles, seemed to indicate that the 

 larva was carnivorous, but the slowness of its move- 

 ments was hardly to be reconciled with this notion. 

 I offered it Insects and plants, but it refused to touch 

 them. This made me conclude, taking into account 

 its uncommon size, that the time for its transforma- 

 tion had come. I therefore put it upon freshly turned 

 up soil, on which I scattered some grass. It made a 

 hole, which it lined with the grass, and remained 

 within it several days in a curved position, lying on 

 its back. When touched it moved actively, but soon 

 resumed its first attitude. 



" On the 2nd September, by which time the larva 

 had greatly diminished in size, the skin split along 

 the back up to the head, and there came out a white 

 pupa, which had been wounded on the right side, 

 from which a brown fluid exuded. This wound, how 

 caused I do not know, led to the death of the animal, 

 which happened some weeks afterwards without 

 further change of form. 



" Some naturalists would not hesitate to conclude 

 from these facts that the larva in question must be 

 terrestrial, since it was found upon the earth ; further, 

 that it must be a vegetable feeder, for it was creeping 

 among the grass and was too heavy to pursue other 

 animals. It is wise, however, to suspend our judg- 

 ment until the facts are perfectly ascertained. Both 

 these conjectures prove to be erroneous. The larva 

 is not terrestrial but aquatic ; it does not feed upon 

 grass but upon animals. 



' In the beginning of July I had noticed in the 

 ditches a kind of cocoon which I did not recognise. 



