352 



The larva is elongated, convex, thick or swelled in the middle and tapering 

 towards the extremities ; it is of a brownish color above, and whitish be- 

 neath. The neck is distinct, the head large, with a pair of powerful curved 

 jaws, that are adapted for suction, being hollow within, and perforated near 

 the tips with an oblong slit. Like most other larvae, it is furnished with 

 several small eyes, five or six in number on each side of the head. To each 

 of the three first segments nearest the head is attached a pair of slender 

 legs, finely fringed with hairs. There are six spiracles on each side of the 

 body, for the purpose of expiration. The last segment is conical, the sides 

 fringed with hairs, which give it the power of a fin, it is terminated at tip 

 with two conical prominences, each perforated with a spiracle, through, 

 which the air is admitted in inspiration. Beneath the tip, and forming an 

 angle with the body are two movable, slender and short, conical filaments. 

 These caudal processes serve to suspend the larva at the surface of the 

 water, and retain the end of the tail above it, so that the air may enter the 

 anal spiracles when the insect wishes to inhale it. They are called natatory 

 lamina; by Mr. Kirby, and are supposed by him to be employed as oars in 

 swimming; this, however, appears to be principally performed by the vermic- 

 ular motion of the tail. 



Several accounts are given of the voracity of these larvae. Some of the 

 large species attain to two and a half inches in length, and are said to 

 attack and destroy fishes much their superiors in size. Having fixed their 

 strong curved jaws in their prey they suck their juices through these per- 

 forated organs, and afterwards devour their solid parts piecemeal. 



Beside those described here, several other Dytisci are found in this vicin- 

 ity; namely, Dytiscus vertical's, Say, and another equally large species; 

 Dytiscus liberus, Colynibetes venustus, C . fenestralis , C. obtusatus, Laccopliilus 

 maculosus, Haliplus 12-punctatus, of Mr. Say; and various other species at 

 present undetermined. 



If among the insects which we have already or may hereafter publish as 

 new there are any which have been previously described; those who are 

 competent to decide are most respectfully requested to communicate per- 

 sonally with us on the subject, and their information will be duly and thank- 

 fully acknowledged. 



GENUS COLYMBETES. 



C. *sulurellus. Beneath black; head and thorax pale testaceous, the 

 former with two triangular spots between the eyes, the latter with an oblong 

 apical and basal spot black ; elytra with about four series of punctures, pale 

 ochreous, and (except the margins and suture) with numerous confluent tor- 

 tuous lines and spots black ; pectus pale ochreous ; feet pale piceous. 



Length between eight and nine twentieths of an inch. 



