) AQUATIC BEETLES 35 



specialised, seems to require air for the discharge of 

 its pecuHar functions. 



The wings and wing-covers of the adult Insect are 

 much like those of other Beetles, but the legs are very- 

 peculiar. The third pair are broad and shaped like 

 paddles. They can deal a powerful backward stroke 

 upon the water with the broad side, and can be 

 drawn up again edgewise with greatly less resistance. 

 The effectiveness of the paddle is enhanced by the 

 long stiff hairs which fringe it, and especially by the 

 peculiar form of the tarsal joints. These are 

 expanded, and so articulated that the fulcra upon 

 which they turn come near together. The effect is 

 like that of the ivory tablets used for memoranda, 

 which are held together by a pin, so that they can 

 either be opened fanwise or closed in a moment. It 

 is impossible to study the action of the limb in the 

 swift darting movements of the Gyrinus, but the 

 power of instantaneous extension or collapse must 

 be of great practical service. The middle legs are 

 also expanded, but in a less degree. The fore legs 

 are prehensile. In the male the tarsal joints are 

 dilated, and bear a great number of circular organs, 

 commonly called suckers, which are, it is believed, 

 used to grasp the female. 



Several Beetles have been observed to make a 

 squeaking noise, and among the number are Dytiscus 

 and Gyrinus. The sound is produced by rubbing the 



antenna;] are furnished with an auricle at their base, which 

 like the Hd of a box, shuts them in when unemployed, and 

 protects them from the water." — Kirby and Spence, Vol. III. 

 p. 516 (1S26). 



D 2 



