io8 



MOLLUSC A, INSECTS, ETC. 



savageness of the larva of Dyticus. It is interesting 

 to watch the Hydrous lay its eggs, in a kind of silken 

 cocoon, spun by the mother. In this cocoon the eggs 

 float about until they are hatched. Curiously enough 

 this beetle swims by alternate movements of its legs. 



The smooth surface of most ponds may often be 

 seen streaked by the mazy paths of the whirligig 

 beetles (Gyrinidcs). Other and not uncommon water 

 beetles are the Colymbetes, related to the Dyticus. 



The Hemiptera, or water bugs, are represented in 

 most ponds by the water scorpion (Nepd), and water 

 boatmen. The former (which is engraved in Fig. 54 

 as being attacked by a Dyticus larva) is itself so 

 voracious as to have obtained the popular name it 



Fig. 58. 



Fig. 60. 



Fig. 61. 



Colymbetes. 



Water Boatman 

 (Notonecta}. 



Notonecta. 



bears. It will float in the summer sun for hours at a 

 time, in a complete invert attitude ; but soon and 

 rapidly moves when disturbed. One or two of these 

 insects may be safely placed in a large tank, especially 

 where there are too many tadpoles, as they keep the 

 latter down by feeding on them. The water boatmen 

 (Notonecta) are also hemipterous insects, deriving their 

 Latin generic name from their habit of swimming on 



