COLEOPTERA. 367 



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. 



DYTISCTJS, Geoff. 



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

 terior 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 particularly, they are enabled to 

 swim with gre.it 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 underneath; those of the first pair particularly are very 

 remarkable in the larger species, these three joints forming there a large 

 palette, the inferior surface of which is covered by little bodies, some in 

 the form of papillae, 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, particularly 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, and propels its body forwards; the lat- 

 ter is usually terminated by two conical, bearded and movable filaments. 



These larvae suspend themselves on the surface of the water by means of 

 two lateral appendages at the extremity of their body, which they keep 

 above it. When they wish to change their position, they communicate a 

 sudden vermicular motion to their body, and strike the water with their 

 tail. They feed more particularly on the larvae of the Libellulae, and those 

 of the Culices and Aselli. When the period of their metamorphosis hag 

 arrived, they issue from the water, and having gained the shore, penetrate 

 into the earth, which must, however, be constantly moistened, or very hu- 

 mid. They then excavate an oval cavity, and shut themselves up in it. 



According to Roesel, the eggs of the D. marginalis are hatched from ten 

 to twelve days after they are laid. In four or five days after this epoch, 

 the larva is already five lines in length, and undergoes its first change of 

 tegument. The second ensues at the expiration of a similar period, and 

 the animal is then double its former size. Its final length is two inches* 

 They have been observed, in summer, to enter into their pupa at the end of 

 fifteen days, and to become perfect insects in fifteen or twenty more. 



This great genus is now divided into several, Dytiscus proper, Colymbetes, 

 HygroUa, &c. 



The second genus of the Hydrocanthari, or the 



