SEXUAL SELECTION 893 



mentioned Leptorhynchus, are larger and more powerful 

 insects than the females. The two sexes of Lethrus cepha- 

 lotes (one of the Lamellicorns) inhabit the same burrow, and 

 the male has larger mandibles than the female. If, during 

 the breeding-season, a strange male attempts to enter the 

 burrow, he is attacked ; the female does not remain passive, 

 but closes the mouth of the burrow, and encourages her 

 mate by continually pushing him on from behind; and the 

 battle lasts until the aggressor is killed or runs away.™ 

 The two sexes of another Lamellicorn beetle, the Ateuchus 

 cicatricosus, live in pairs, and seem much attached to each 

 other ; the male excites the female to roll the balls of dung 

 in which the ova are deposited; and if she is removed, he 

 becomes much agitated. If the male is removed the female 

 ceases all work, and, as M. Brulerie" believes, would remain 

 on the same spot until she died. 



The great mandibles of the male Luanidas are extremely 

 variable both in size and structure, and in this respect re- 

 semble the horns on the head and thorax of many male 

 Lamellicorns and Staphylinidae. A perfect series can be 

 formed from the best-provided to the worst-provided or 

 degenerate males. Although the mandibles of the common 

 stag-beetle, and probably of many other species, are used 

 as efficient weapons for fighting, it is doubtful whether their 

 great size can thus be accounted for. We have seen that 

 they are used by the Lucanus elaphus of North America for 

 seizing the female. As they are so conspicuous and so 

 elegantly branched, and as owing to their great length they 

 are not well adapted for pinching, the suspicion has crossed 

 my mind that they may in addition serve as an ornament, 

 like the horns on the head and thorax of the various species 

 above described. The male Ghiasognaihus grantii of South 

 Chile — a splendid beetle belonging to the same family — 

 has enormously developed mandibles (Fig. 24); he Is bold 



™ Quoted from Fischer, in "Diet. Class. d'Hist. Nat.," torn. x. p. 324. 

 " "Ann. Soc. Eutomolog. France," 1866, aa quoted in "Journal of Travel," 

 toy A. Murray, 1868, p. 135. 



