30 LUCANID^ AND PASSALID^, 



for the mandibles, a better adaptation for such use would in 

 time result from the operation of the selective process, as 

 has happened to some horn-forms in Coprine beetles, but 

 evidence of such adaptation is not easily to be found in 

 LucANiD^. It may be noted that the alternation of the teeth 

 upon the opj)osed mandibles to be observed in females, which 

 increases their gripping jjower, usually persists in those of 

 males not in a very advanced condition , but is often replaced 

 in the most highl}^ developed condition by complete symmetry, 

 the gripping power being sacrificed because unrequired. 



It is natural to seek for some practical explanation for 

 these highly-developed and therefore apparently important 

 organs, and many have been suggested. Major Kingston, 

 in ' The meaning of Animal Colour and Adornment,' has put 

 forward the view that their use is protection by the intimidation 

 of their enemies. " Some male stag-beetles have enormous 

 jaws, extravagant far bej^ond physical needs . . . they possess 

 the same attributes that characterise the antlers of stags , . . 

 they are now mainly intimidating instruments " (p. 267). 

 The rapid multiplication which is liable to occur in insects 

 accidentally introduced into a fresh habitat shows that the 

 effective enemies are not those which can be described as 

 casual but those which have a well-established habit of preying 

 upon them, and a fallacious appearance unrelated to any real 

 threat would have little effect upon these. In addition, there 

 are grounds for believing that the males of many of these beetles 

 much outnumber the females and, since the latter, which 

 need it more, are without such protection, the effect upon the 

 future generation would in any case not be important. 



Although it appears strange that organs of no real importance 

 should, notwithstanding, attain the size and fantastic appearance 

 seen in some of these beetles, it must be remembered, first, 

 that a greater increase in these organs is found to be an invari- 

 able accompaniment of the increase in body-size which has 

 happened to these large insects ; and, secondly, that, being 

 confined to the males, it has no effect upon the perpetuation 

 of the species and is, in consequence, uncontrolled by Natural 

 Selection. 



Classification. 



Those members of our two groups which were knowTi to 

 Linnaeus were included by him in his great genus ^Scarabn7is. 

 From this the genus Liicanus was separated in 1763 by Scopoli 

 and the genus Passahis in 1792 by Fabricius. In 1819 

 Macleay devised a single group, which he called Recticera 

 thalerophaga, to comprise the two families Lucanid^ and 

 Passalid^, to which he added for certain aberrant forms 

 now included in the former, three more famihes (^salid^, 

 Syndesid^ and Lamprimid^) in accordance with his con- 

 ception of the " quinary " system of Nature. The quinary 



