244" CLASS INSECTA. 



with palpi, and six simple eyes on each side, approximating 

 closely. They have six feet, tolerably long, often fringed 

 with hair, and terminated by two small claws. They are 

 agile, carnivorous, and respire either by the anus or by spe- 

 cies of fins which imitate gills. They come out of the water 

 to be metamorphosed into nymphs. 



This tribe is composed of two principal genera. 



Dytiscus, 



Which have the antennae like threads, longer than the head, 

 two eyes, the anterior feet shorter than the following, and the 

 last most frequently terminated by a compressed tarsus, 

 going in a point. They swim with much swiftness by the 

 assistance of their feet, furnished with long hairs, and parti- 

 larly with the last two. They dart on other insects, aquatic 

 worms, &c. In the majority of the males the four anterior 

 tarsi have their first three articulations widened, and spungy 

 underneath. Those of the first pair are especially remark- 

 able in the larger species. These three articulations form 

 there a large palette, the inferior surface of which is covered 

 with small bodies, some like papillae, and others larger, and 

 in the form of suckers, &c. Some females are distinguished 

 from their males by furrowed cases. The larvae have the 

 body composed of from eleven to twelve rings, and covered 

 with a scaly plate. They are long, big-bellied towards the 

 middle, more narrow at the two extremities, particularly be- 

 hind, where the last rings form an elongated cone, furnished 

 on the sides with a fringe of floating hairs, with which the 

 animal pushes the water and causes his body to advance, 

 which is usually terminated by two conical threads, barbed, 

 and mobile. Between them are two small cylindrical bodies, 

 pierced with a hole at their extremity, and which are aeri- 

 form conduits, to which the two trachea lead. Stigmata, 

 however, are distinguishable on the side of the abdomen. 



