COLEOPTERA. 407 



entirely covered ; the body is always oval, the eyes but slightly pro- 

 minent, 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 Geoffrey. 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 

 rises occasionally to the surface of their liquid abodes in order to 

 respire ; this they easily effect by keeping their head motionless, and 

 permitting themselves to float. Their body being reversed, they 

 elevate its posterior extremity a little above the water, raise the ex- 

 tremity 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 excepting 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 mandibles, 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 by the anus or by a kind of fins re- 

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

 leave the water. 



This tribe consists of two principal genera : 



DYTISCUS, Geoff. 



The Dytisci have a filiform antennae longer than the head, two 

 eyes, the anterior legs shorter than the following ones, and the last 

 most commonly terminated by a compressed tarsus ending in a point*. 

 By means of their legs fringed with long hairs, the two last particu- 

 larly, they are enabled to swim with gruat 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 



According to M. Leon Dufour, their crop is terminated behind by an annular 

 roll (bourrelet) a character not found in the preceding tribe. Their crccum forms a 

 natatory bladder. Their pectus contains two pneumatic sacs, while the tracheae of 

 the other parts are tubular. The adipose splanchnic tissue possesses the characters 

 of a true epiploon or mesentery. Their stigmata also differ from those of the 

 Terrestrial Carnivore. 



