1 86 WONDERS OF POND LIFE. 



The representatives of two tribes of these aqua- 

 tic beetles are now under our observation. Here 

 is one rising to the surface with a bit of meat in 

 its tarsi twice as Jarge as itself. Its store of air 

 is exhausted, and it must needs be replenished 

 before it has completed its meal. How it ever 

 manages to lift the hinder part of its body clear 

 from the water is more than we can tell, but such 

 is the fact. Then slightly raising its wing-covers 

 it admits the air between them and the abdomen, 

 tightly pressing the last segment against the elytroji 

 at the close of the operation, thus forming a perfect 

 air-tight cavity, and confining the new supply to 

 be breathed up through tubes situated along the 

 sides of the body. Now it skurries away to the 

 bottom to recommence its work as a scavenger, 

 creeping into every nook and corner, peeping into 

 the doorway of the caddis-worm's house, or lying 

 in wait to pounce upon the mussel whenever it 

 shows its dainty foot outside its shell. I have 

 watched it thus for fifteen minutes before it again 

 rose to the surface to lay in another light, but 

 valuable cargo of air. 



Another beetle in this tank, of the same family, 

 but belonging to a different genus, is the Gryrinus, 

 or whirliwig, a surface-swimmer, never diving to 



