l|i AQUATIC BEETLES 69 



head six small black points, which are the eyes. 

 The head, as it becomes hard, turns black, and it is 

 then difficult to see without a microscope that there 

 are any eyes at all." 



Lyonnet reared Hydrophilus larvae in order to 

 observe the process of pupation and the form of the 

 pupa, but found unexpected difficulties in his way. 

 "One larva," he says, "left the water on the ist 

 of July, and travelled about my room. I put it back 

 into the aquarium. Some hours later another came 

 out, which I put into a trough with earth and grass. 

 It lived only two days, and such was also the fate of 

 two others. On the 20th of July I supplied earth to 

 two more, freshly emerged from the water, one of 

 which was larger by a quarter of an inch than the 

 other. They burrowed into the earth, and remained 

 there seven or eight days, when the smaller one came 

 out, and burrowing again at least three inches deep, 

 made a cell in which it stayed for two or three days, 

 lying on its back. Either my too frequent attempts 

 to see it, or some other circumstance, caused it to 

 destroy its cell, and this Insect also perished. About 

 the same time another larva which had begun to 

 make a cell destroyed it, apparently for the same 

 reason, and formed a fresh hiding-place in the earth. 

 There it made a new cell with a place of escape 

 on one side. On the 24th of August I removed 

 the earth which concealed it, and found the Insect 

 changed into a white pupa, though it was unable to 

 free itself from the larval skin. I endeavoured to 

 help it. It was easy to remove the bits of old skin 

 which clung to its body, but I did not venture to 



