THE WHIRLIGIG BEETLE. 81 



them the appearance of arms ; they are probably of 

 service in feeding. The two hinder pairs of limbs, on 

 the contrary, are very short, but much flattened, 

 and greatly dilated, so as to become most powerful 

 paddles ; and it is by the action of these that the little 

 creatures are enabled to perform those rapid gyrations, 

 which, coupled with their sociable habits, and the 

 high polish of their surface, render them such pleasing 

 objects when engaged in their lively dance on the 

 surface of a quiet pool. 



The commonest British species, the Gyrinus natator, 

 above alluded to, may be seen sporting on the surface 

 of every quiet piece of water, generally in a sheltered 

 situation close to the bank. It is about a quarter of 

 an inch in length, of an oval form, and entirely of a 

 black colour, with the exception of the legs, which 

 are pale rusty red. The elytra, as usual in this group, 

 are a little shorter than the abdomen, and the insect 

 is tolerably convex above, so that when the sun shines 

 upon its highly polished surface, the light is reflected 

 with a dazzling brilliancy, which has been compared 

 to that of polished silver. The structure of the eyes 

 of the Gyrinus is admirably fitted for its peculiar 

 mode of life; as it performs its graceful evolutions 

 upon the surface of the still water, it has always one 

 pair of eyes on the look-out for danger approaching 

 from the regions of the air, whilst the other pair is as 

 busily engaged in watching the transactions in the 

 water beneath it. We may easily convince ourselves 

 that these sentinels are faithful to their duty, for if 

 we approach too closely to their aquatic ball-room, 

 the whole company will immediately disperse, the 

 majority plunging down into the deep water, carrying 

 a small bubble of air attached to their hinder extre- 



E5 



