82 NATURAL HISTORY OF AQUATIC INSECTS CH. 



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. 

 I found to my surprise that, like a Spider, she had her 

 spinneret at the hinder end of the body. By extend- 

 ing the hinder rings ever so little, and opening the 

 last of all, a nearly circular cavity appeared, in which 

 I could discover a whitish disc. From this two small 

 brown prominences were given off side by side. 

 Each enclosed a delicate conical tube, about a line in 

 length, and of dark-brown colour, stiff towards its 

 base, flexible and elastic towards the tip. These two 

 tubes formed the spinneret, and each contributed a 

 separate thread. They moved both together, and 

 exactly parallel to one another. 



" The construction of the floating cocoon was 

 effected in the following way. At first, lying upside 

 clown near the surface of the water, the Beetle 

 buried the hinder part of her body and the two 

 hindermost pairs of legs in the alga, leaving the first 

 pair free, and making use of them to fit and mould 

 the alga to the end of her body. She then began 

 to weave the under side of her cocoon. While the 

 weaving was going on, she was careful from time to 

 time to press and flatten the growing cocoon, mould- 

 ing it with her fore feet against her body, and so 

 giving it the form of a flattened arch. After the first 

 piece, which was intended to form the upper side of 

 the cocoon, was finished, the Beetle turned over and 

 wove another piece, exactly the reverse of the first, to 



