WONDERS OF POND LIFE. 187 



the bottom excepting when very much alarmed, 

 and then quickly taking its bubble with it, it 

 descends like a pebble thrown into the water by a 

 sling, striking its chitinous shell against the glass 

 with such force as to be distinctly heard. After 

 awhile it clings to the spray of a submerged water- 

 cress, remaining ten minutes in this position, and 

 affording us an excellent opportunity of noting the 

 difference of structure in the genera. Unlike 

 the Dyticus, the first pair of legs are long, and the 

 hinder pair are very short and changed into oars, 

 and what is still more singular, it has four eyes, 

 two above and two below, by which the insect can 

 sight its prey or enemies in the air or water. 

 Some flies are thrown in the tank. How it goes 

 at them, tearing away the legs and wings with its 

 sharp mandibles, and lapping in the life-giving 

 juices — a prisoner's fare indeed. 



A species of beetle, from the family HydropMlus, 

 Avhich I suspect to be a vegetable feeder, and per- 

 haps not more than half-aquatic, moves around 

 awkwardly in the aquarium. It is able, however, 

 to remain a long time under water, for its entire 

 under part is covered with a thin bubble which 

 looks as if a lining of quicksilver had been put 

 there. The longer hind legs are not flattened into 



