18 



back close against the joint bearing it, which has a corresponding 

 excavation of its inner face, so that a, locking apparatus results. 

 A further development occurs in genera like Peperonota and 

 Didrepanephorus (fig. 6), in which the tip of the enlarged claw when 

 folded back meets a prolongation of the penultimate joint having 

 the frrrn of a broad plate, the surface of which bears closely-set 

 parallel ridges beautifully adapted to prevent the slipping of the 

 object grasped in the vice. The shortening and thickening of the 

 legs is evidently 1 a means of obtaining increased muscular power 

 and the dilated claw no doubt provides inside a larger surface 

 for muscle attachment. The modification sometimes affects the 

 middle as well as the front claw, and in Popillia ettpricottis, 

 P. marginicollis and a few allied species, the two anterior pairs of 

 legs are altogether much stouter than those of the female, which, 

 howe\er, has very powerful hind legs, with tarsi shorter and 

 thicker than those of the male. 



Fig. 6. Front tarsus of Didrepaiiepharus bifalcifer, male. 



The enlargement in the male of the inner claw results, in genera 

 in which that claw is ordinarily cleft, in the inequality of the two 

 divisions and a tendency to the dwindling or even the complete 

 disappearance of the outer branch. Jn many species of Anomala 

 and Adoretus only a minute vestige of it is traceable in this sex, 

 and in various others, the females of which have a cleft claw 

 upon each of the four anterior feet, the males have either all 

 simple or those of the front feet only cleft. The latter condition 

 is that most prevalent in the genus Popillia. It may therefore 

 be stated as a genera] rule that, when the two sexes differ in this 

 respect, the claws of the female are more divided than those of 

 the male. But it is a remarkable fact that in the PARASTASIINJ, 

 the many structural peculiarities of which denote habits quite 

 different from those of the rest of the subfamily, this rule is 

 reversed. Sexual differences here also are numerous, and the 

 claws exhibit a variety of different combinations ; but it is in the 

 females that we here find all the claws undivided, while the males 

 often have the longer one deeply cleft. To increase the contrast, 

 the front claws, which in the other groups are the most generally 

 divided, are here most often undivided, while the hindmost, 



