296 TRANSFORMATIONS OF INSECTS. 



in contact with the respiratory orifices. The beetle is equally- 

 interesting when it is about to lay its eggs, and whilst it is forming 

 its cocoon. Crawling over the aquatic plants head downwards, it 

 lays its eggs and immediately drags its silk-drawers over and 

 around them, and it envelopes them in a cocoon, which it fixes 

 either to a leaf or to a stem. But sometimes the cocoon floats 

 by itself. These cocoons are of a light grey colour, are a short 

 oval in shape, and have a long conical pedicle. 



The beetle on the leaf close to the surface of the water, in 

 the engraving on the previous page, is laying its eggs and forming 

 its cocoon. Another beetle is on the ground on the left hand ; 

 a nymph is enclosed in its cell on the right, and above it there is 

 a full-grown larva. 



EGG COCOONS OF HydropJiihis pice2is. (Magnified.) 



As soon as the young larvse are hatched they begin to feed, 

 and grow very rapidly ; and when they have attained their full 

 size they are large insects of a dark grey colour, and the hard 

 parts of the head and of the thorax are of a lustrous brown tint. 

 Whilst they are quiet, and even during their progression, the head 

 and the tail are turned up so that the body is always more or less 

 curved. They swim easily with the assistance of ciliated legs and 

 a flexible abdomen. The nymph has some very strong and thick 

 hairs on the thorax and abdomen, but their use is unknown. 



The central cocoon represented in the above engraving is 

 attached to a leaf, but that on the left hand is isolated. On the 

 right hand a cocoon has been opened so as to show the position 

 of the eggs in it. 



The DytiscidcB live in most stagnant waters, and in the little 

 streams which roll slowly along on account of their water weed. 

 These beetles arc provided with large wings, with which they can 



