58 COMMON BRITISH INSECTS. 



The COMMON WHIRLIGIG, Gyrinus natator, is 

 very gregarious in its habits, and may generally be 

 seen in small companies, whirling about on the surface 

 of the water in very still and sheltered places. As 

 they dart about, they often strike against each other ; 

 but the shock does no harm to their hard and polished 

 bodies, and they go on with their unceasing round as 

 if nothing had happened. Their chief object in thus 

 continually darting over the surface is to obtain food, 

 which consists principally of small flies, Beetles, and 

 other insects which fall into the water. They use 

 their long fore legs in the capture of prey. They are 

 watchful little Beetles, and if they fear danger they 

 dive to the bottom, and there remain until they think 

 that they can return in safety to the surface. 



The life history of the Gyrinus is rather a curious 

 one, and is much the same with all the species. The 

 eggs are deposited on a water-plant, and laid in 

 regular rows. From them, in a week or a little more, 

 the curious larvae are hatched. The larva is dirty- 

 white in colour, and has a large, flat, oval head, armed 

 with powerful jaws, and six rather long legs ; while 

 from each side of the eight last joints of the body 

 proceeds a very slender filament, which is part of the 

 respiratory system. The last segment has two pairs 

 of these filaments, each of which is seen, on being 

 viewed by the aid of the microscope, to contain an 

 air-tube, which passes into the body and there joins 

 the general system. When in the water its appear- 

 ance is very much like that of a centipede, except 

 that the respiratory filaments have no independent 



