362 INSECTA. 



The body is usually ovoid or hemispherical, convex or arched. The legs in 

 several are adapted for swimming, and then consist of but four very distinct 

 joints, or of five, the first of which is much shorter than the second; all 

 the joints are entire. 



Those in which the legs are natatory, have the first joint of the tarsi much 

 shorter than the following ones, and the maxillae are entirely corneous, these 

 will form our first tribe, that of the HYDROPHIUI, which embraces the genus 



HYDROPHILUS, Geoffrey. 



Linnicus merely made these Insects a division (the first) of his genus Dytiscus, 

 but their anatomy is essentially different. In the true Hydrophilus the sternal 

 spine is strongly prolonged behind. The last joint of the two anterior tarsi of 

 the males is dilated in the form of a triangular palette. The scutellum is 

 large. 



The larvte resemble a sort of soft, conical, and elongated worm, furnished 

 with six feet, and a large squamous head, more convex underneath than above, 

 armed with strong and hooked mandibles. They respire by the posterior 

 extremity of the body, are very voracious, and do great injury to fish ponds by 

 devouring the spawn. 



H. picens, Fab. An inch and a half long; oval; of a blackish-brown, 

 polished, or as if covered with a varnish; antennal club partly reddish ; some 

 slightly marked striae on the elytra, the posterior extremity of which is rounded 

 laterally, and prolonged into a small tooth at the internal angle. 



It swims and flies well, but walks badly. When held loosely in the hand, 

 its sternal spine sometimes inflicts a wound. 



The extremity of the female is provided with two fusi, by means of which 

 she constructs an ovoid cocoon, surmounted with a point, resembling an arcu- 

 ated brown horn. Its external tissue is a gummy paste, which, though fluid at 

 first, subsequently hardens, and becomes impervious to water. The ova it con- 

 tains are arranged symmetrically, and kept in situ by a sort of white down. 

 These cocoons float on the water. 



The larva is depressed, blackish and rugose, and has the faculty of throwing 

 back its brown, smooth, round head. This enables it to capture the little 

 Mollusca which navigate the surface of the water, its back serving as a point 

 d'appui or anvil on which it mashes the shell in order to devour the animal it 

 contains. The body of these larvae becomes flabby as soon as they are caught. 

 They swim with great facility, and are provided with two fleshy appendages 

 which serve to maintain them on the surface of the water, head downwards, 

 when they come there to respire. According to M. Miger, the larvae of other 

 Hydrophilii are deprived of these appendages, and neither swim nor suspend 

 themselves like those of which we have been speaking. The females of these 

 species swim with difficulty, and carry their ova under the abdomen enclosed 

 in a silken web. 



There are many other genera of Hydrophiliaus, such as Hydrochus, Octhe- 

 bius, Spercheus, &c., differing in form, the arrangement of the antennas, &c. 



