COLEOPTERA. 345 



The Pentamerous Aquatic Carnivora form a third tribe, that of the HYDRO- 

 CANTH AM, Lat. The feet of these insects are fitted for natation ; the four last 

 are compressed, ciliated, or laminiform, and the two last at a distance from the 

 others; the mandibles are almost entirely covered; the body is always oval, the 

 eyes but slightly prominent, and the thorax much wider than long. The 

 terminal hook of the maxillae is arcuated from its base; those at the extremity 

 of the tarsi are often unequal 



They compose the genera Dytiscus and Gyrinus of Geoffroy. They pass 

 their first and last stage of existence in the fresh and placid waters of lakes, 

 marshes, ponds, &c. They are good swimmers, and rise occasionally to the 

 surface of their liquid abodes in order to respire; this they easily effect by 

 keeping their legs motionless, and permitting themselves to float. Their body 

 being reversed, they elevate its posterior extremity a little above the water, 

 raise the extremity of their elytra, or depress the end of the abdomen, in order 

 that air may enter the stigmata, which are covered by them, whence it finds 

 its way to the tracheae. They are excessively voracious, and feed on small 

 animals inhabiting the same element, which they never leave except during 

 the night, or at its approach. When taken from the water they diffuse a 

 nauseating odour. They are frequently attracted into houses by the light of 

 candles, &c. 



Their larvae have a long and narrow body composed of twelve rings, the 

 first of which is the largest; a stout head, provided with two powerful mandi- 

 bles, curved into an arc, and perforated near the point ; small antennae, palpi, 

 and six simple approximated eyes on each side. They have six tolerably long 

 legs, frequently fringed with hairs, and terminated by two small nails. They 

 are active, carnivorous, and respire either at the extremity or by a kind of fins 

 resembling branchiae. When about to enter into their pupa state they 

 leave the water. 



This tribe consists of two principal genera. 



DYTISCUS, Geoffroy. 



The Dytisci have filiform antennae longer than the head, two eyes, the ante- 

 rior legs shorter than the following ones, and the last most commonly termi- 

 nated by a compressed tarsus ending in a point. By means of their legs 

 fringed with long hairs, the two last particularly, they are enabled to swim 

 with great velocity. They dart upon other insects, aquatic worms, &c. In 

 most of the males the three first joints of the four anterior tarsi are widened 

 and spongy underneatli ; those of the first pair particularly are very remarkable 

 in the larger species, these three joints forming there a large palette, the infe- 

 rior surface of which is covered by little bodies, some in the form of papillag, 

 and others, larger, in that of cups or suckers, &c. The body of the larva is 

 composed of from eleven to twelve annuli, and covered with a squamous plate; 

 this larva is long, ventricose in the middle, and slender at each end, particu- 

 larly behind, where the last annuli form an elongated cone furnished on the 

 sides with a fringe of floating hairs, with which the animal acts on the water, 



