COLEOPTEEOTJS INSECTS. 135 



genus in the family, is that first established by 

 Linne* under the name of 



DYTISCUS, 



a term derived from fiurijg, which signifies a diver. 

 In its present restricted form, it is distinguished by 

 having the antennae setaceous, that is, tapering slight- 

 ly from the base to the apex ; by the truncated ter- 

 minal joint of the labial palpi ; and by having the 

 anterior tarsi dilated in the males into a rounded 

 plate. The three basal joints of the tarsi are di- 

 lated in the middle pair of legs — a circumstance 

 which chiefly discriminates the Dytisci proper from 

 the genus Acilius of Dr Leach — and the elytra of 

 the female are usually furrowed. 



The larvae are narrow and elongate, composed of 

 twelve segments, including the head, which is large 

 and strong, bearing short antennae, and armed with 

 two powerful jaws. The last named organs, which are 

 long and incurved, are perforated at the tip, so that 

 they not only serve to seize and lacerate the prey, 

 but also form a tube through which its juices are 

 absorbed. The anal segment is slender and co- 

 nical, and is furnished with two projecting appen- 

 dages, by means of which the animal is enabled 

 to push itself forwards in the water, and rise to 

 the surface for a supply of fresh air. The three 

 segments behind the head are each provided with 

 a pair of legs, which are more or less fringed with 



