ON THE PALPICORNES. 441 



shells become more heavy immediately after the birth of 

 these larvae. He explains this fact, by supposing that there 

 is then introduced by the points, a greater quantity of air. 



The eggs disclose the young generally in the space of 

 from twelve to fifteen days, at least in the month of May, 

 which was the time in which M. Miger made his observa- 

 tions. The young larvae have scarcely quitted their nest, 

 than they are seen to re-enter there, issue forth anew, and 

 sport all around it, up to the moment when the want of 

 nourishment obliges them to separate. 



These larvae change their skin several times in the water, 

 and in the usual manner. Those which M, Miger attempted 

 to rear, at their issuing from the egg, perished, probably 

 from not having had the sort of nourishment which was 

 suitable to them. But he preserved many of those which 

 he had taken at a more advanced age, and which were more 

 robust. They did not make at first, when they were seized, 

 any motion to defend themselves ; but soon after they made 

 themselves so flaccid, that he imagined that he was touching 

 nothing but a simple spoil. Taken by the tail, they imme- 

 diately contracted themselves, and lost nearly one third of 

 their length. They became quickly agitated, and squirted 

 forth, with a slight noise, from the posterior extremity of 

 their body, a fetid, and blackish water. We know that 

 many other aquatic larvae have the faculty of drawing in, 

 and rejecting water by their hinder part. The larvee of the 

 libellulinge make use of it to carry them forwards. Those 

 of the dytisci thus humectate their bodies when, being out of 

 the water, they are exposed to too great a heat. It appears 

 that those of the hydrophili employ this means for defend- 

 ing- themselves. 



M. Miger put these larvae into fresh spring water. They 

 swam there with great facility, agitating their feet in a 

 lively manner. They often came to the surface to respire. 



