194 



THE BOOK OF NATURE STUDY 



which is familiar on the surface of slowly flowing water and of 

 ponds. They dart about like water-sprites, " so swiftly, in fact, 

 that, when disturbed the eye can hardly follow their motions." 

 When danger threatens they dive among the water-weed or to the 

 bottom, taking down with them a quicksilver-like bubble of air 

 attached between the tips of the wing-covers and the tail-end of 

 the body. 



Fowler l gives the following diagnosis : " Ovate, convex, 

 upper side bluish-black with the sides brassy ; elytra punctate, 

 striate, the internal striae much fainter than the external ; under 

 side black, with the margins of the elytra and the legs red or 



reddish, testa- 

 ceous, sometimes 

 the breast and 

 apex of the ab- 

 domen are red. 

 In Scotland the 

 whirligig is usu- 

 ally narrower, 

 with the sides 

 more rounded, 

 and the internal 

 striae towards the 

 base of the wing- 

 covers are very 

 faint, or want- 

 ing." 



Our point here is that it will be well to make as sure of this 

 extremely common water-beetle as one is sure of a water-hen, 

 and to use it as an object for careful study. At this stage that 

 will be more useful than trying to know a lot of beetles. There 

 are scores of things to find out about Gyrinus, how it gets from 

 pond to pond, how it holds on below water, what happens when 

 you hold it in your hand, what it eats. Then there is the remark- 

 able, somewhat centipede-like larva to look for, and the cocoon 

 it makes on the rushes, and so on. 



Pond-Skaters. Very characteristic of the surface of pools are 



1 See (Fowler) p. 222. 



FlG. 112. i, Caddis cases ; 2, larva taken out of the cases 

 3, pupa ; 4, full-grown caddis-fly. 



