94 COMMON BRITISH INSECTS. 



surface for the purpose of respiration ; and they con- 

 trive to carry down a supply of atmospheric air by 

 enclosing a bubble under the bodies, where it looks 

 like a globe of quicksilver as they swim about. As 

 this species is not only handsome but harmless, it is 

 in great favour with the keepers of aquariums, and is 

 in consequence quite scarce in many places where it 

 used to be plentiful, the professional dealers having 

 ransacked all the streams within easy reach of 

 London. 



THE family next in order, the Sphaeridiidae, or 

 GLOBE BEETLES, are distinguished from the preceding 

 family by the shape of the tarsi, which are not fitted 

 for swimming, and the hinder pairs of which members 

 have the first joint much longer than the others. They 

 are all small insects, rather globular in form, from 

 which peculiarity the name of the family is derived ; 

 and they are dark-coloured, black being the usual hue, 

 relieved in some species by reddish spots. In the 

 genus Cercyon, from which our example is taken, the 

 club of the antennae is large and bold, the palpi are 

 slender, and the mentum is broad 

 and flat. 



As is the case with most red and 

 black Beetles, the colour is exceed- 

 ingly variable in different indivi- 

 duals, so different indeed, that the 

 present species, Cercyon anale, a 

 figure of which is herewith given, 

 Cercyon anaie. has been described under four 

 separate names, each name being used to represent 



