WATEE-BBETLES. 



207 



favotirite attitude of this larva is to float, head downwards, 

 with its caudal appendages just touching the surface of the 

 water. It does not swim, so fast as, nor are its jaws so strong 

 as those of, the perfect insect. It changes its skin from time 

 to time, according to its growth. The food of the animal 

 consists of small fish, tadpoles, insects, and larvse of insects. 

 Two of these creatures will never live long together in the 

 same vessel, for sooner or later one will be almost certaia to 

 eat the other. They may be fed upon 

 garden-worms, but they do not care 

 very much for them. They seem to 

 prefer Corixse to any other food, and 

 it is rather surprising to see how 

 cleverly the comparatively slow-mov- 

 ing animals are able to catch the fleet 

 ones. 



If it be wished to give these larvae an 

 opportunity of becoming beetles while 

 in confinement, it will be necessary to 

 prepare an aquarium especially for the 

 purpose. The tank for this arrange- 

 ment should be rather large, andjbefore 

 the water is introduced-flr-bafik of soil, 

 sand, and gravel should be built at 

 one end. When the water is put in 

 it must be in such a quantity that it 

 will not cover all of the sloping bank. 

 A very fine siphon ought to be used 



or the water will not be clear. The larva spends about a 

 fortnight in its pupal state. 



The aquarium-keeper will find that this beetle and its larva 

 are very interesting. Of course the two must never be kept 

 together, or the latter will never have the chance of becoming 

 the perfect insect. 



I have written so much concerning J), mwrginalis because its 

 habits are more or less characteristic of its smaller relatives. 



There ai-e five other species of the genus Dytiscus, very 

 like ia appearance and habits to the D. marginalis ; but none 



Fig. 132. Lauva of the 

 Wateb-Beetle (Dytis- 

 cus MARGINALIS). 



