DYTISCIDiE. 
273 
The elytra cover the abdomen and the wings are large and functional 
in all species. The anterior legs are set close together, of the usual form 
except in the males, in which the 
basal tarsal joints are to a greater 
or less extent dilated; in some this 
dilation is so large as to form a 
conspicuous sucker-like organ and 
used by the male to securely hold 
the female. The hind legs are long 
and formed for swimming, the tarsi 
compressed and twisted so that the 
upper edge is outward ; they are 
ciliated on one or both edges. The 
coxae are very large and occupy a 
large part of the ventral surface. 
The sexes are similar in general 
appearance and are distinguished 
by the fore tarsi. These beetles 
excrete a whitish fluid from the 
articulation of the head and pro¬ 
thorax on being seized, and also 
excrete an unpleasant fluid at the 
anus. 
The life-history of no species appears to have been worked out in India 
and there is no reason to believe it differs from the general type. Eggs 
are laid in aquatic plants, under water, and hatch into elongated grubs 
with a large flat head, a long tapering body terminating in two ciliated 
processes ; there are three pairs of long swimming legs. The apex of 
the abdomen ends in two spiracles which alone are open and functional; 
the larva comes to the surface tail upwards, the two processes lie flat 
on the surface film owing to their ciliations and support the 
grub, which takes in the air supply quickly. The head has a pair 
of long hollow sickle-shaped mandibles, and it has been shown that 
when these are in use the mouth is automatically closed ; the larva 
grasps its prey by the mandibles, inserts them and sucks the blood 
through the hollow mandibles; the larvae are extraordinarily voracious, 
and if confined together, attack and destroy one another. They are 
II l 18 
Fig. 154.—Cy bister confusus, male. 
