340 THE DESCENT OF MAN, 



tioiied Leptorhynchus, are larger and more powerful insects 

 than the females. The two sexes of Lethrns cephalotes 

 (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 females 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 Lucanidae are extremely 

 variable both in size and structure, and in this respect 

 resemble 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 elai^lius 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 Chiasognathus 

 Granfii of S. Chili a splendid beetle belonging to the 

 same family has enormously developed mandibles (fig. 24); 

 he is bold and pugnacious; when threatened he faces round, 

 opens his great jaws, and at the same time stridulates 

 loudly. But the mandibles were not strong enough to pinch 

 my finger so as to cause actual pain. 



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

 324. 



f " Ann, Soc. Entomolog. France," 1866, as quoted in "Journal of 

 Travel," by A, Murray, 1868, p. 135. 



