30 



THE AQUARIUM. 



yellowish down. The female covers her eggs up in a 

 silken bag which floats upon the surface until the eggs 

 hatch. 



Of a far different character is the Great Water-beetle 

 {Dyticus marginalis)^ of which a figure is given. It is 

 about an inch in length. In this species there is con- 

 siderable difference in the appearance of the male and the 

 female. The male is represented in the annexed figure, 

 and its wing-cases, or elytra, are smooth^ whilst those of 

 the female are deeply furrowed. In addition, the male 



has a different formation of the 

 fore-legs, a portion being flattened 

 out into a cushion bearing suckers 

 on its under surface. Throughout 

 its life this beetle is equally vora- 

 cious, for the larva in an aquarium 

 is as destructive as a tiger would 

 be in a sheep-fold. It has a long, 

 narrow, flexible body, and its head 

 is furnished with a couple of sharp, 

 curved jaws, which move over each 

 other like the blades of a pair of 

 shears. These jaws are hollow, 



Dyticus marsinalis. ^^^^ ^j^^^ ^^^^ pierCCd an 



enemy its blood is sucked through them. 



It is impossible for us, in the necessarily restricted 

 space at our disposal, to enter into a description of the 

 various species of water-beetles, but they will all be found 

 to possess a considerable amount of interest if kept in a 

 special vessel. There is a common species known as 

 Aciliits siilcatiLS, with rather flat, brown wing-cases, deeply 

 furrowed longitudinally. There are the various species of 

 Hydrophilous and of Agabiis. Nor should we forget the 



