SWIMMING ANIMALS. 45 



are not swimmers, and, therefore, do not come within 

 the scope of the present article, those of the Gnats are 

 endowed in great perfection with the power of swim- 

 ming. With their large heads and their tapering 

 bodies, these ugly larvae are probably familiar to most 

 of us, swimming about in ponds and tanks with great 

 agility by a sudden jerking motion of the body, or at 

 intervals suspending themselves head downwards at 

 the surface of the water for the purpose of breathing 

 through a tube situated in the tail. Other insects are 

 aquatic in the adult state. Some of the commonest 

 British examples are the "Water-Scorpion (Nepa) and 

 Water-Boatman (Notonecta), both belonging to the 

 order Rhynchota. These swim by means of the hind 

 legs, which are, however, scarcely fringed in the former, 

 although markedly so in the latter. The Water- 

 Scorpion has two tail-like organs at the end of the 

 body, which, when put in opposition, form a tube 

 through which the creature can breathe without com- 

 ing quite to the surface. The Water-Boatman, as its 

 scientific name implies, has the curious habit of swim- 

 ming on its back; when at rest for the purpose of 

 taking in a fresh supply of air the long hind legs are 

 extended nearly at right angles to the body, and thus 

 recall a boatman resting on his oars. 



The remaining aquatic insects are the Water- Bee ties 

 (Coleoptera), of which there are several families, in 

 all of which both the larvae and adults are aquatic, 

 although the pupae are quiescent and lie hidden in 

 holes in the ground. The Water-Beetles are easily 



