362 THE WORLD OF ANIMAL LIFE 



THE GREAT WATER-BEETLE (Family Dytiscid^) 



It is a warm, sunny morning in autumn, and we are standing 

 on the bank of a small weedy pond, in readiness to see whatever 

 there is to be seen. No breath of wind is stirring, and there is 

 not a ripple upon the water. Suddenly we notice a disturbance. 

 A small black object appears above the surface, a curious popping 

 sound is heard, and then with a kick and a struggle the small black 

 object disappears. 



This is a Great Water-Beetle, which has been diving, and has 

 just come up to obtain a* fresh supply of air. Let us see what there 

 is to learn about him. 



His two hindmost legs are broadened and strengthened into 

 oars, and they are fringed with stiff hairs to make them more 

 serviceable. 



These oar-like limbs are naturally of very little use to the 

 beetle on dry land. If he is taken from the water and placed upon 

 the ground, he can only shuffle awkwardly along, like a seal or a 

 walrus in similar circumstances. But as he is very seldom obliged 

 to travel upon land, this defect is of little importance. 



Although they live in water these beetles are true air-breathers. 

 They keep a supply of air underneath their hard wing-cases, or 

 elytra. 



Experiments have been made for the purpose of ascertaining 

 how long one of these beetles could remain beneath the surface 

 of the water. One has been kept under water for an hour and 

 twenty-seven minutes without being killed, that is, stifled for 

 want of air. 



The breathing-holes of the water-beetles are placed upon the 

 back instead of along the sides of the body as in most insects, so 

 that respiration can be carried on while the insect is under water. 



These beetles often leave the water, and at night they climb 

 out and set off for a journey in the air. Their wings are large 

 and broad, and carry them swiftly and easily along; and in this 

 way they travel from one pond to another. 



If we take a beetle from a pond, allow him to become dry. 



