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58 INSECTS AT HOME. 



is sure to take to its wings and fly off in search of more food. 

 Even gold fish have been attacked by this insatiate devoiirer, 

 which does not even spare its own kind, and devours the oppo- 

 site sex a's well as its own. When these Beetles take flight 

 from the pond or stream in which they have been living, they 

 always crawl up a reed or a water-plant, so as to gain space to 

 spread their beautiful wings. In consequence of this freedom 

 of locomotion, this Beetle may be found in almost any pond, 

 however small i1? may be. Even when ponds have been* reduced 

 to mere puddles by the drought of summer, the Dyticus may 

 be found plentifully, hiding itself in the still soft mud. 



The mode in which this insect breathes is really wonderful. 

 Being "an insect, it is forced to breathe atmosjaheric air, and 

 yet it has to pass the greater part of its time under water. 

 The problem is solved by the Beetle converting itself for the 

 nonce into a diving bell, receiving the supply of air as often as 

 needful. This feat is accomplished in the following way : — The 

 I body is rather flat, so that there is a space between the folded 

 ' wino-s and the elvtra. Now, these elvtra are very lar^e, 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 breath- 

 ing 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 Avith their heads downwards, 

 I 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 

 j -strange position. All the Dyticidje employ this cm-ious mode 



-of supplying themselves with air, but it is most conspicuous in 



-the larger species, and is therefore described in connection 



■with this Beetle. 



There is a rather remarkable point in the structure of the 



v.wings. On the inside of the elytra, and at their bases, is a 

 pair of membranous plates with finely-fringed edges, something 

 like wings, for which reason they have been called ' alulets,' or 



i,iittle.,wings. These cannot be seen while the insect is at rest, 



