COLEOPTEEOrs INSECTS. 
137 
DYTISCUS DIMIDIATUS. 
PLATE IV. Fig. I. 
Bergstraesser Nomenclature pi. 7? fig* 1* — Curtis' Brit. Ent . 
iii. pi. 99. 
The colour is brownish black tinged with olive 
green. The antennae and upper lip are yellow, and 
there is a triangular or crescent-shaped spot of rust 
red on the forehead between the eyes. The thorax 
is widely margined on each side with yellow, and a 
broad stripe of the same colour runs along the whole 
of the external margin of the elytra : the surface of 
the latter is very smooth in the males, and each is 
marked with three rows of punctures. The under 
side of the body, and the legs, are yellowish, with 
the sutures of the breast black. The lobes of the 
sternum, which afford very distinctive characters in 
this group, are obtuse in the present species. 
It has occurred at Cambridge, and in some other 
parts of England. 
There is another group of aquatic beetles, the 
species of which, although much inferior in size to 
those just described, are still more fitted to attract 
attention by their numbers, brilliant appearance, and 
interesting manners. These insects constitute the 
genus 
