52 COMMON BRITISH INSECTS. 



part of its time under water. The problem is solved 

 by the Beetle converting itself for the nonce into a 

 diving bell, renewing the supply of air as often as 

 needful. This feat is accomplished in the following 

 way: The body is rather flat, so that there is a 

 space between the folded wings and the elytra. Now 

 these elytra are very large, and, when closed, are 

 quite air-tight. When the Beetle wishes to breathe, 

 it comes to the surface of the water with its head 

 downwards, and just exposes the tip of its abdomen 

 to the air. In a moment it has expelled the air which 

 has already been used in breathing, and taken in a 

 fresh supply, with which it dives to the bottom. As 

 the spiracles, or mouths of the breathing tubes, open 

 into the space between the elytra and the abdomen, 

 they can take in the air, and pass it through the 

 system. Sometimes, if the observer will approach 

 very quietly, he may see the Beetles floating with 

 their heads downwards, the tips of their tails just 

 above the surface of the water, and their hind legs 

 spread out so as to balance the body in this strange 

 position. All the Dyticidae employ this curious mode 

 of supplying themselves with air, but it is most con- 

 spicuous in the larger species, and is therefore de- 

 scribed in connection with this Beetle. 



Having now glanced at the history of the perfect 

 Beetle, we will turn to its larval existence. 



There is no possibility of evading the fact, that 

 the larva of the Dyticus is ugly. It is very ugly. It 

 is the crocodile of the insect world, lying unseen in its 

 muddy bed, and darting out at any luckless insect 

 that may pass near it. 



