BEETLES 



365 



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male being covered with two rows of swimming-hairs, of which the female has but 

 one. In swimming, the middle legs, which are provided with a smaller number of 

 hairs, are used to steer with, the front legs being nearly always occupied in catch- 

 ing the prey and conveying it to the mouth. The body, which is unusually flat, 

 is well adapted for cleaving the water. The larvae are obtainable from stagnant 

 water in the spi-ing, and are among thfl largest inhabiting fresh water : when fully 

 grown they are a little 

 over two inches long, and 

 recognisable by their 

 large scythe-shaped upper - - 

 jaws, the inner side of 

 which is toothless, as well 

 as by the absence of any 

 real mouth, and the flat- 

 ness of the head. When 

 the larvae rise to breathe, 

 they are obliged to hold 

 their breathing - pores, 

 which are situated at the 

 end of the last ring of the 

 body, above the water, and, 

 in doing so, the insect, 

 which is then twisted into 

 a double curve, hangs on 

 to the surface by means of 

 certain appendages at the 



THE GREAT BROWN WATER-REETLE. 



back of the body which 



are stretched flat on the water. When disturbed in this position, it drops suddenly 

 some distance into the water, with a vigorous movement of the hind part of the 

 body. The larva swims quietly about, using its hair-covered legs as oars, and 

 lives a life of voracity, not like the beetle devouring its prey, but sucking out the 

 juices with the help of the upper jaw, on the inside of which is a groove, open at 

 the top and leading into the alimentary canal. For their metamorphosis into 

 pupas the larvae go on land. 



Whirligig Some of the most extraordinary of all aquatic insects are the 



Beetles. whirligig-beetles, which are sociable insects, swimming about in tine 

 weather on the surface of the water in wavy cross-lines and spiral curves. These 

 beetles not only swim on the surface, but dive in search of food and to protect 

 themselves from bad weather or threatening danger. The eyes are strikingly 

 adapted for a life between air and water, the beetle being enabled to see its sur- 

 roundings both above and under water, owing to the circumstance that each eye 

 is divided by a broad ridge into two separate portions, one situated on the upper 

 side of the head and the other beneath. One pair of these divisions is used for 

 observing objects above the water, and the other for those beneath ; a similar 

 arrangement existing in a species of fish living oft* the coasts of South America, 

 where it swims on the surface. The legs are so entirely adapted for swimming 



