INTRODUCTION. l5 



give it a form entirely unlike that of the female. The enlarge- 

 ment of the head may entail the widening of the thoia.\ in 

 front. The great develo])inent of the anterior j)art of the 

 body throws forward its centre of gravity and necessitates 

 an adjustment of the suj)ports, and the fore-legs are therefore 

 relatively longer in the male. \'aiious other differences are 

 no doubt due to the different habits of tlie two sexes, the 

 females being more sedentary and usually under the necessity 

 of burrowing for the deposition of their eggs, wiiile the males 

 need no adaptation for that j)urpose and are more active. 

 The legs of the females are accordingly stout and formc^d for 

 digging, while those of the males are slender and sometimes 

 extremely long. 



In the genus LucanuH the contrast between the very elongate 

 legs of the males and the short and ]iowerful legs of the females 

 is complete and an almost equally striking dissimilarity is 

 found in many of the species of Calcodes. A curious exception 

 to the general rule occurs in the wide-ranging Gnaphaloryx 

 opacus, Plate XV, figs. 11-13, of which the female has the 

 front tibiae more slender than the male and strongly curved — 

 no doubt an adaptation to some unusual mode of life. (A 

 rather similar form is found in another peculiar and apparently 

 rare little Indian species, Dorcus curvipes). The middle and 

 hind tibiae of the female may have stout lateral spines which 

 are absent or feeble in the male, those of the male may have 

 hairy pads, as in Calcodes marginatus, or notches, as in Dorcus 

 hiplagiatus , which are absent in the female. In some species 

 of Calcodes the prosternum is produced in the male. 



There are many other differences between the sexes, of a 

 very varied kind and affecting almost every part of the bod}- . 

 It is rather remarkable that the abdomen, which in other 

 Lamellicorns is especially apt to show such differences, is 

 here almost the only exception. In Dorcus macclellandi 

 there is a tufted process at the extremity of the abdomen of 

 the male, but I know of no similar case. In some species of 

 Lucanus the male has a remarkably long clypeal process or 

 clypeo-labrum and in various forms of Dorcus the corres- 

 ponding part, instead of being lengthened, is very much widened 

 in that sex. It might reasonably have been suj^posed that 

 the presence or absence of so well-developed a structure as the 

 forked process, very conspicuous in the male Lucanus lunifer, 

 would afford an important means of grouping the species 

 but, like so many other features, the dypeus of the male is 

 liable to an extreme variability. Its development closel}' 

 follows that of the mandibles and it may be narrow or broad, 

 according to the distance separating these at their bases in 

 different individuals. In Dorcus tifnnus it may be deeply 

 divided or entire ; in the Malayan Calcodes somnuri, loivci and 



