58 NATURAL HISTORY OF AQUATIC INSECTS CH. 



hold a Gyrinus with the suckers of the fore tarsi 

 until it was devoured. It may be doubted, however, 

 whether the peculiar suctorial structure is useful in 

 this connection ; it is certainly not necessary, for the 

 females have no suckers at all. When grasping the 

 female, the fore suckers are applied to the smooth 

 prothorax, and the middle suckers to the unfurrowed 

 margin of the elytra. 



The males of many land Beetles (Carabidae, Cicin- 

 delids, Silphidae, and Meloidae) possess suckers, as 

 well as male Dytiscidae and Hydrophilidae, which are 

 aquatic. 



We have next to notice the time-honoured ex- 

 planation of a contrivance supposed to be accessory 

 to the action of the suckers of the male Dytiscus. 

 Kirby and Spence ^ tell us that " the elytra of the 

 females of many of the larger water beetles {Djtisais) 

 are deeply furrowed, while those of the males are 

 quite smooth and level. . . . Another aquatic Beetle, 

 Acilms snlcatus. Leach, has not only its elytra 

 sulcated, but the furrows of these and a transverse 

 one of the thorax are thickly set with hair ; while 

 the male is smooth and quite naked. Particular care 

 seems to have been taken by the Creator that when 

 all the above inhabitants of the water are paired, the 

 male should be able to fix himself so firmly, by means 

 of his remarkable anterior tarsi . . . and these as- 

 perities, etc., in the upper surface of his mate, as not 

 to be displaced." 



Further inquiry has greatly shaken an intcrpreta- 



^ Vol. III. p. 305 (1826). The authors mention the occasional 

 occurrence of smooth females. 



