8o OUR INSECT FRIENDS AND FOES 



at the base of her abdomen, and with their aid 

 she produces the silky bag or cocoon in which 

 she encloses her eggs. The celebrated Lyonnet's 

 name will always be associated with the study of 

 this interesting Beetle, on account of the beauti- 

 ful and accurate drawings he made of the insect's 

 anatomy, and his methodical observation of every 

 stage of its life-history. I therefore give the 

 following quotation from Lyonnet's historic 

 narrative, in which he describes most graphically 

 the way in which the female forms her cocoon : 

 " I was particularly anxious to ascertain how the 

 females constructed the floating cocoon which 

 encloses their eggs. For this purpose I placed 

 a few of these insects with some duck-weed in 

 a large wooden trough on the last day of May. 

 On the ist of June I saw that one of the females, 

 contrary to its usual custom, was incessantly 

 swimming about, and searching on all sides. I 

 expected that this was because she did not find 

 materials suitable for her work, and as I had 

 often seen a filamentous alga attached to the co- 

 coon, it occurred to me to give her some of this. 

 I floated it on the water by means of wooden 

 shavings, and next day, the $rd of June, I found the 

 beginning of a cocoon, but the insect had aban- 

 doned her work, apparently because she had 

 been disturbed by several other kinds of aquatic 

 insects which lurked in the weed. I took them 

 out of the trough, and before long had the 

 pleasure of seeing the female Hydrophilus 

 betaking herself to work under my eyes. 



" The construction of the floating cocoon was 

 effected in the following way. At first, lying 



