86 THE PHILHYDRIDA. 



in length. This is generally about the month of July, 

 when the larva creeps out of the water, forms an oval 

 chamber in the bank, and there passes to the pupa 

 state. In this condition it remains about a month, 

 when it casts its skin for the last time, but as its 

 parts are then soft and weak, it wisely remains for 

 ten or twelve days in concealment before venturing 

 amongst the manifold dangers of the world. 



An interesting circumstance connected with the 

 oviposition of this insect, is, that the female encloses 

 her eggs, which are fifty or sixty in number, in a sort 

 of cocoon formed of a gummy matter, and lined with 

 a delicate white silk. The substance of which this 

 cocoon is composed, is spun from a pair of minute 

 tubular organs situated at the extremity of the abdo- 

 men, and by means of it the female is enabled to 

 suspend her eggs to the stems of aquatic plants. 



Most of the other aquatic species of Philhydrida 

 present a considerable resemblance to the Great Water 

 Beetle both in structure and habits. Their larvae are 

 generally carnivorous, whilst the perfect beetles are 

 for the most part contented with vegetable food. 

 Their power of swimming, however, is usually very 

 small, their legs being rather adapted for crawling 

 upon aquatic plants than for natatory purposes, and 

 the smaller species (such as the Hydrobii and Helo- 

 phori) may be constantly seen struggling manfully 

 in the water, working away with their little legs in a 

 most earnest fashion, but scarcely progressing a 

 couple of inches in five minutes. 



If this be the case with many of the typical Phil- 

 hydrida, it is still more decidedly so with the beetles 

 with short palpi, which, as has already been stated, 

 are associated with this group. Many of these, 



