INTRODUCTION. 27 



and elytra, which were evidently produced by the middle 

 teeth of the mesodont form " and he figures the elytra of a 

 specimen of C cuvera with six symmetrically arranged wounds ; 

 but he has overlooked the fact that no weapon can ])ierce 

 any surface except upon an opposed plane. The two mandibles 

 of C. cuvera could not possiblj^ both pierce the smooth upper 

 surface of another specimen symmetrically and at the same 

 time, and therefore these symmetrical marks must certauily 

 be due to some other cause. Such marks, which 1 have seen 

 in other beetles, 1 believe occur in the pupal state and I am 

 inclined to attribute them to the attack of a fungus. 



There seems, indeed, to be an almost complete lack of 

 evidence for either of Darwin's suppositions, put forward in 

 support of his theory of Sexual Selection, that larger mandibles 

 afford advantage to their possessor in combat with other 

 males, or that thej' constitute an attraction for the femajes. 

 Mr. R. E. Parsons, who for several days observed many speci- 

 mens of Dorcus foveatus, large and small and of both sexes, 

 which had the habit of congregating uj)on a particular Citrus 

 tree in Assam, found that in the cases he noticed " it was 

 the small males that mated with the females and the large 

 males did not seem to want to interfere with the mating of 

 the small males and did not disturb the latter and their 

 consorts." 



It may almost be said that the possible efficiency of the 

 male mandibles as weapons is in inverse proportion to their 

 size, for, the muscular force being applied at the base, the 

 pressure that can be exerted at the other end diminishes in 

 proportion to the length. In the primitive state the jaws of 

 the male, as well as those of the female, were no doubt efficient 

 biting organs, but the process of elongation, although sometimes, 

 as in the genus Lucanus, accomjjanied by an increase in the 

 size of tlie head, as thougli in an effort to maintain muscular 

 strength, has generally involved a progressive diminution in 

 biting or gripping power, so that it might be said that the 

 insects as a consequence are preserved from such injuries as 

 are often inflicted by insects with jaws of normal size. The 

 Chihan Chiasognathus granti, perhaps the most extravagantly 

 armed of all Lucaniu.^, the jaws reaching a length greater 

 than that of the bod}', was subjected to experiment by Darwin 

 himself, who has recorded that " the mandibles were not strong 

 enough to pmch my finger so as to cause actual pain." As a 

 beetle "s exterior is far better protected than the human 

 finger and the jaws of Chiasognathus bear numerous fine 

 teeth needmg httle pressiu-e to penetrate the finger, we cannot 

 suppose them to be of importance as weapons. 



There is still less reason to regard the male mandibles as 

 constituting an attraction for the other sex. Apart from the 



