Chap. X.] COLEOPTERA. 365 



corn 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 de- 

 posited ; and, if she is removed, he becomes much agita- 

 ted. If the male is removed, the female ceases all work, 

 and, as M. Brulerie 66 believes, would remain on the spot 

 until she died. 



The great mandibles of the male Lucanidse are ex- 

 tremely 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 with the I/ucanus elaphus of 

 North America they are used for seizing the female. As 

 they are so conspicuous and so elegantly branched, the 

 suspicion has sometimes crossed my mind that they may 

 be serviceable to the males as an ornament, in the same 

 manner as the horns on the head and thorax of the 

 various above-described species. The male Chiasognathus 

 grant ii of South Chili — a splendid beetle belonging to the 

 same family — has enormously-developed mandibles (fig. 

 23) ; he is bold and pugnacious; when threatend on any 

 side he faces round, opening his great jaws, and at the 

 same time stridulating loudly; but the mandibles were 

 not strong enough to pinch my finger so as to cause 

 actual pain. 



Sexual selection, which implies the possession of con- 

 siderable perceptive powers and of strong passions, seems 

 to have been more effective with the Lamellicorns than 



66 'Ann. Soc. Entomolog. France,' 1866, as quoted in ' Journal of 

 Travel,' by A. Murray, i868, p. 135. 



