ON THE PALPICORNES. 439 



which it possesses, and by the continued movements in all 

 directions which the insect can communicate to it, concurs 

 principally to the execution of the work. It is it which puts 

 in action the two spinnerets. 



The air which the hydrophili possess the faculty of keep- 

 ing in reserve, under their elytra, and which is often ob- 

 served in the form of a bubble, serves them for the purpose 

 of respiration while they are forming their shells, and pre- 

 serves their eggs from the dangerous influence of the water. 

 It has been said that these shells floated isolatedly on the 

 water, and that the horn or point Avhich terminates them, 

 served as a sort of mast for this little skift". This, however, 

 only happens when they are empty, for M. Miger has found 

 always, that a shell filled with eggs is overturned by its own 

 weight, and that the insect has always need of a support, 

 such as dry or living plants, to lay the foundations of its 

 edifice. He thinks, with reason, and as had been already 

 suspected, that this point of the shell is destined for the 

 introduction of air. The examination of the nature of the 

 kinds of fluids, of which the shells are composed, seems 

 also to strengthen this opinion. The liquid which serves to 

 form the external tissue is a sort of liquid and gummy paste, 

 which is melted, and amalgamates with all that surrounds 

 it, and which becomes, by dessication, a tolerably flexible 

 envelope, but at the same time so compact, that it hinders 

 the water from penetrating into the interior. The second 

 fluid, that which envelopes the eggs at the instant of their 

 emission, is a slight down of great whiteness, which keeps 

 them in their places, and without which they might be 

 bruised. Finally, the fluid of which the point is composed, 

 is a silky, porous, and lustrous tissue, very like that of the 

 shells of the lepidoptera. It appears proper for the intro- 

 duction of the air, and the water penetrates it with facility 

 from the moment it is submerged. The shell is ovoid, 



