WATER BEETLES. 47 



familiarly called, have the various portions of the 

 body fitting closely to each other, so as to leave an 

 uniform smooth and polished surface, something like 

 the scaly surface of the fish, the slippery skin of the 

 whales and dolphins, and the close-set fur of the 

 seals. 



The limbs are also modified to suit the special 

 purpose for which they are designed. As these 

 Beetles walk less than they swim, greater provision 

 has been made for the latter mode of progression. 

 Accordingly, the first and middle pairs of legs are 

 comparatively small and feeble, the strength being 

 thrown into the hinder pair, which are large in com- 

 parison with the others, and, in nearly all cases, 

 flattened and furnished with a fringe of stiff bristles 

 on the inner side, so that they serve as oars. They 

 are jointed in a peculiar manner to the body, so that 

 there is room within the thorax for a set of very 

 powerful muscles which work them, and they are 

 placed farther back than is usual among Beetles a 

 peculiarity of structure which is found also in the seals 

 and the diving birds, especially the penguin tribe. 



Although they cannot, as a rule, walk well, they 

 can all fly well, and are furnished with very large and 

 powerful wings, so that, if food should fail them in 

 one piece of water, they can fly to another. They 

 generally fly at night, and have an odd way, when 

 they reach a pond or stream, of closing their wings 

 while high in the air, and allowing themselves to fall 

 like stones into the water. Sometimes, deceived by 

 the glitter in the moonshine, they have been known 

 fall upon the roofs of greenhouses. 



