COLEOPTEROUS INSECTS. 
135 
genus in the family, is that first established by 
Linne under the name of 
DYTISCUS, 
a term derived from $ur qg, 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 
