WATEE-BBBTLBS. 203 



be readily kept in confinement. It is common, tardy, and 

 interesting ; bnt, as already mentioned, it should not be allowed 

 companions during its captivity. It is weU described as the 

 "ogre" among insects; for it is indeed as much a source of 

 fear and danger to the small aquatic animals among which it 

 lives as is the pike — ^the fresh-water shark — ^to its fellow fish. 



The generic name of Dytiscus implies that it and its near 

 relatives are great divers. D. marginalis is nearly the largest 

 of the British aquatic ooleoptera, and it is certainly by far 

 the most rapacious. The strength of this beetle is amazing, 

 as anyone may prove for himself, either by taking it up in 

 his fingers and feeling how strongly it struggles with its 

 posterior legs to escape from the fingers which are pressing 

 each side of its elytra, or by endeavouring to remove the 

 insect while it is clinging with its fore-legs to a water-plant 

 or to the edges of the aquarium. One has read of the stag 

 beetle {Lucanus cervws) pushing along the tumbler under which 

 it was confined; but the water-beetle (B. marginalis) is not 

 far behind its distant relative in physical powers. No 

 wonder that this fresh-water " ogre ". is such a source of terror 

 to its fellows in the pond when its huge strength and great 

 appetite are taken into -consideration.' 



These Dytisci are very abundant, and may be obtained in 

 most weedy ponds and ditches ; but one must acquire a little 

 adroitness with the water-net before one can be sure of catching 

 them, for they are very wary and quick, diving to the bottom 

 on the first sign of danger, and remaining there clinging 

 to some weed or stone. They are obliged to thus anchor 

 themselves, for otherwise, while remaining motionless — as they 

 are specifically lighter than water — they would rise to the 

 surface. A good plan of capturing these and other aquatic 

 beetles is to go quietly to the side of a pond, stand there 

 with the net in readiness, and, as these air-breathing insects 

 make their necessary ioumeys to the surface, place it gently 

 under them as they dive down with their fresh supply of air. 

 This method of capture does not disturb either the water of 

 the pond or its inmates. These beetles will be often seen, 

 especially if the weather be fine, floating, close to the surface, 



