124< MODERN CLASSIFICATION OF INSECTS. 



motions are equally awkward. They generally keep in the water by 

 clay, but may occasionally be seen sitting upon plants by the water's 

 edge ; they, however, come abroad in the evening, and take wing. 

 On again seeking the water, they cannot dive without difficulty, owing 

 to the dryness of their bodies. 



The relationship of these insects with the Dyticidae has already 

 been noticed ; indeed, both families were originally united in the same 

 genus. The anterior tarsi of the males of the typical species are also 

 singularly dilated ; but it is the terminal joint only, and not the basal 

 ones, as in the Dyticidae, which exhibits this peculiarity. The sternum 

 of the thoracic segments is greatly developed ; that of the metathorax 

 terminating in a long and acute spine, extending beneath the abdo- 

 men [Jig.S. 6. Hydrocharis caraboides). 



According to M. Dufour, Dutrochet, in his observations on the 

 metamorphoses of the alimentary canal of insects {Journ. de Physique, 

 Mars, 1818, in which the digestive organs of Hydrophilus and its larva 

 are purported to be described), has fallen into the error of describing 

 the organs of a Dyticus instead of a Hydrophilus [Recherch. Anat. sur 

 les Carab., Szc. p. 37-). 



The preparatory states of various species have been observed by 

 different entomologists, especially Rosel, Miger, and Lyonnet. The 

 females of the largest species, Hydrophilus piceus, possess the singular 

 habit of spinning a gummy envelope for their eggs ; and in this sex 

 we find the excremental intestine replaced by organs for the secre- 

 tion of the matter for the formation of such envelope, the anus being 

 also furnished with two spinnerets. The eggs, fifty or sixty in num- 

 ber, are disposed symmetrically, and in an upright position, in their re- 

 ceptacle, which has somewhat the appearance of a small turnip, being 

 nearly an inch broad^ and which is attached to some plant until the 

 larvae are hatched, when it floats about on the surface of the water. 

 The larvae escape at the lower part of the cocoon, which is closed only 

 by a few threads ; one side is furnished with an upright bent horny 

 point, an inch long, which has been supposed to act as a sail, being 

 elevated above the surface of the water ; but, from the observations of 

 M. Miger, such cannot be the case, as the cocoons are invariably af- 

 fixed to plants ; he therefore considers it as serviceable in conveying 

 air to the interior ; indeed, on detaching a cocoon filled with eggs, the 

 side from which the point arises is immediately submerged by its su- 

 perior weight. The exterior surface hardens, and becomes impene- 



