^6 LTJCANTDiE AND PASSALID^. 



has an exaggerated armature the evidences of labour are 

 found in the females alone." 



In the LucANiD^ female specimens are often found in which 

 the front tibiae show some amount of wear, although probably 

 few have occasion to i:)erform such strenuous labours as are 

 the lot of many Coprin^. Male Lucanids, however, although 

 their tibial teeth are usually very sharp and spine like, seem 

 never to show any signs of wear, clear evidence that the 

 females alone perform the labours necessary to ensure the 

 existence of the progeny. Inheritance by that sex in any 

 degree of the extravagant mandibular developments of the 

 male would prevent the proper performance of those functions 

 and ultimate^ entail the extinction of the species ; but, so 

 long as the inheritance is confined to the male, the well-being 

 of future generations is not affected. Unless the extravagance 

 reaches a point at which locomotion becomes difficult, it 

 seems to entail no particular disadvantage, as comjoared with 

 other insects in which such a tendency is absent. But in 

 the Passalid^, the mandibles of both parents being important 

 for the well-being of the young, the manifestation of a similar 

 tendency in one sex or both would result in endangering the 

 perpetuation of the species. Only races in which no such 

 tendency existed would ultimately survive. In other words, 

 the complete contrast between the two groups in this respect 

 seems to me to be best explained by the operation of natural 

 selection. 



As to the significance of the great mandibles of male Stag- 

 beetles, the arguments adduced in my previous volume, in 

 considering the horns of the Coprin^, apply equally to these. 

 Those arguments led me to reject both the sui^jjosition that 

 such ajjpendages can be adequately explained as weapons, 

 offensive or defensive, and that put forward by Darwin, 

 that they may serve as ornaments attractive to the other sex. 

 The accoiuits of contests, which have often been observed 

 between the males of the European Lucanus cerviis, do not 

 indicate that their mandibles show any adaptation for fighting 

 or can be accurately described as effective weapons. Some 

 forms, like Hexarfhrivs parryi with stout sharp-pointed jaws, 

 appear capable of inflicting more serious injuries, and scratches 

 are sometimes found upon these, but I have found none but 

 of a suj^erficial kind. The progressive elongation of the jaws, 

 characterizing most forms, entails diminished instead of 

 increased offensive power. 



Leuthner, in his ' Monograph of the Odontolabini,' (Trans. 

 Zool. Soc. xi, 1885, ji. 40J, note) speaks of "numerous 

 injuries observed in specimens of (Calcodes) alces of all 

 sizes ; some of these consisted of deep punctures and 

 indentations, generally in pairs, on the hard prothorax 



