191:^] on The Life-History of a Water-Beetle 759 



This last stage is also divisible into two parts, the first occupying 

 four or five weeks, during which the larva feeds and grows as in the 

 previous stages, the second occupying two to four weeks, being spent 

 out of the water making a cell in the earth, and resting preparatory 

 to becoming a pupa. 



In the few cases which I had the opportunity of observing, the 

 full-grown larva always left the water in the morning between eight 

 and ten o'clock ; but whether this is the rule with this species, or 

 whether it was connected with the artificial conditions in which my 

 larvse were reared, I do not know. 



Once the larva leaves the water it crawls about very actively, 

 seeking a suitable place to enter the earth. If left to itself it usually 

 selected a stone and burrowed underneath it, but I found that if I 

 made an artificial burrow — with a pencil, for instance— the larva could 

 be made to crawl into this, and as a rule would make its " cell " in 

 it. By making such a burrow against the glass side of a box filled 

 with earth, I was able to watcli the process of the formation of the 

 pupal cell. 



Once the larva has entered and adopted the burrow, it straight- 

 way begins to prepare its cell, and this is done by enlarging part of 

 the burrow. The jaws are now used for transporting pellets of soil 

 from one position to another and for breaking up the pellets into 

 their separate particles. Very little earth is actually pushed into the 

 unused part of the burrow, the cell being formed almost entirely by 

 breaking up the pellets of soil and battering tiie fine particles against 

 the sides. The vertex of the head is the main battering-ram, but 

 the larva, which during the whole process of making the cell lies 

 with its tail bent over its head, also flattens out the earth with its 

 l)ody. 



The actual making of the cell occupies about twelve hours, and 

 dui'ing that time the larva does not rest for a moment. At the end 

 of tliat time it is apparently tired out, and rests in any position, often 

 stretched across the cell, its head pressed against one side and its 

 curved body against the other. It thus rests for about twenty-four 

 hours, after which it ))ends its tail underneath it and usually adopts 

 a sitting-up position— reminding one of Tennicl's illustration in 

 " Alice in AVondcrland " of the caterpillar sitting on the nmshroom. 

 It is, however, very restless, and frequently changes its position, 

 tossing from side to side. 



The pupa, appears, after the larva has been thus resting for a fort- 

 night or more, by the larval skin splitting along the back and being 

 cast olf at the tail end. On its back are to be seen a number of 

 short projecting spines, and Lyonnet suggested in the case of another 

 pupa, similarly though better equipped, that these are for the purpose 

 of raising it off the damp soil of the cell. This may be true, but in my 

 experience the pupa most usually lies, so to speak, on its face rather 

 than on its back. 

 Vol. XX. (No. 107) 3 e 



