HYDRADEPHAOA. 
77 
three (and in Cnemidotus six) segments of the abdo- 
men. 
They are all small, ovate, and convex ; mostly light 
yellow in colour, varied with obscure darker patches. 
One species, Brychius elevatus, is more elongate and 
flatter than the rest, and is also more distinctly 
marked ; it has strong longitudinal ridges on its elytra, 
and long straggling legs, and may be found in running 
streams, clinging to stones and weeds. Another, 
Haliplus obliquus (Plate III., Fig. 4), is prettily 
spotted ; it occurs in stagnant water. 
The Pklobiid.'k, represented by one species, Telobiux 
tardus ( Ilermanni ) (Plate III., Fig. 5), have the an- 
tennae eleven -jointed, the hinder coxae not produced 
into a plate, but enlarged in front, the scutellum dis- 
tinct, tarsi all five- jointed, the head stretched out, 
and the legs adapted more for walking than swimming. 
This insect, commonly known as “ the Squeaker ” 
(about half an inch long, convex, dull black and red 
in colour), is found somewhat plentifully in stagnant 
ponds near London, clinging to weeds, and grovelling 
in mud ; it makes a sharp noise by rubbing the hard 
reflected margin of the last segment of its abdomen in 
a groove under each wing-case. 
The Dytiscid.h have the antennae eleven -jointed, 
glabrous and shining, the maxillae with two lobes, the 
inner or lacinia being curved at the extremity and 
acuminate, and the hind coxae very large, soldered 
with, and appearing part of the metasternum, reaching 
the margin of the elytra when closed ; the posterior 
legs arc modified for swimming by the tibiae and tarsi 
being furnished with swimming hairs, and being 
broadened and flattened ; the posterior tarsi are always 
