366 INSECTA. 



Count Dejean describes one hundred and twenty-four species, which he 

 has arranged in sixteen divisions. The first thirteen comprise those whose 

 elytra are convex or arched, and the three last, those in which they J are 

 plane. 



The greater number of these species inhabit Europe, Caucasus, Siberia, 

 Asia Minor, Syria, and the north of Africa to the thirtieth degree of north 

 latitude. Some few are also found at the two extremities of America, and 

 it is probable that others may be found in the intermediate mountains(l). 



The Pentamerous Aquatic Carnivora form a third tribe, that of 

 the Hydrocanthaei, 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 promi- 

 nent, and the thorax much wider than long. The terminal hook of 

 the maxillsB 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 pla- 

 cid waters of lakes, marshes, ponds, &c. They are good swim- 

 mers, and rise occasionally to the surface of their liquid abodes in 

 order to respire; this they easily effect by keeping their legs motion- 

 less, 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 vora- 

 cious, 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 



(1) Of the species that inhabit North America, we have as yet only dis- 

 covered the C. Seauvoisi, carinatus, Lherminier?, Uneatopundatus {serratus. 

 Say), syhosus and vinctus. The mountains of New Hampshu-e, and Maine 

 particularly, probably contain several otbers, and it is to be hoped that 

 some friend of the science, within reach of those localities, wiU soon enable 

 MS to enlarge our catalogue of this interesting genus, as well as that of 

 otliers found in the same localities. — Am. Ed. 



