84 NATURAL HISTORY OF AQUATIC INSECTS CH. 



on Hydrophilus, Miger l described the life-history of 

 the large Hydrophilus. 



Miger remarks that he was curious to find out how 

 an Insect living under water could construct a cocoon 

 floating on the surface. Early in May 1807 he found 

 several specimens, and placed them in a vessel of 

 water, together with the aquatic plants on which they 

 chiefly feed. At length a female was seen to under- 

 take the formation of a cocoon. Miger saw her 

 attach herself to the under side of a leaf which was 

 floating on the water. She placed her body across 

 the leaf, clasping it with her fore legs. The abdomen 

 was applied to the under surface of the leaf, and the 

 two tubes which form the spinneret could be seen to 

 be pushed in and out rapidly, while a white gummy 

 liquid was passed from them. This liquid was drawn 

 out into threads, which were attached to the leaf, and 

 gradually surrounded the abdomen, forming a semi- 

 circular pouch, in which the tip of the abdomen was 

 contained. After about ten minutes the Hydrophilus 

 turned sharply round, letting go the leaf and bringing 

 her head downwards, but without withdrawing the 

 abdomen from the cocoon. The leaf was now held 

 by the hind legs only, one being placed on each side 

 of the cocoon. The work went on steadily for nearly 

 an hour and a half, and through the transparent wall 

 of the cocoonthe movements of the spinneret could be 

 distinctly seen, until the gradual 'addition of threads 

 made it at last so thick and compact that the move- 

 ments of the spinneret could no longer be distinguished. 



1 Miger 3 s memoir is to be found in Ann. du Museum d?Hist. 

 Nat., Tom. XIV. (1809). 



