BLACK WATER BEETLE. 91 



though it is not so often found as the COMMON PILL 

 BEETLE (Byrrhus pilula}, which is without the yellow 

 band across the elytra. Five species of this genus 

 inhabit England. 



Now we come to a very familiar but little understood 

 insect, popularly called the BLACK WATER BEETLE. 

 Like some of the preceding species, it has been con- 

 founded with the Hydradephaga, merely because it 

 inhabits the water, no reference being made to its 

 structure, or even its mode of feeding. Indeed, I 

 believe that scarcely any, except entomologists, have 

 the least idea that the Dyticus and the present Beetle 

 are not the same insect, the only difference being that 

 one is much larger than the other. Now, if we 

 examine this Beetle, Hydrous piceus, we shall find a 

 vast number of structural differences, as well as com- 

 plete divergence in habits. 



The Beetle belongs to the family of Hydro- 

 philidae, i.e. water-lovers. Sometimes the two halves 

 of the word are transposed, the Beetles being called 

 Philhydrida, the signification being exactly the same 

 in both cases. The family may be known by the size 

 of the palpi, which are as long as the antennae and 

 sometimes longer the latter organs never having 

 more than nine joints, and sometimes only six and by 

 the double lobe of the maxilla and the very short 

 mandibles. The tarsi have five joints. The typical 

 genus has the mandibles armed on the inside with 

 three strong teeth, notched at their tips ; the second 

 joint of the maxillary palpi is very long, and the elytra 

 become narrower towards the apex. 



