296 THE DESCENT OP MAN. 



scheme of nature is liere so far from holding good, that we have 

 a complete inversion of the ordinary state of things in the family. 

 We may reasonably suspect that the males originally bore horns 

 and transferred them to the females in a rudimentary condition, 

 as in so many other Lamellicorns. Why the males subsequently 

 lost their horns, we know not; but this may have been caused 

 through the principle of compensation, owing to the development 

 of the large horns and projections on the lower surface; and as 

 these are confined to the males, the rudiments of the upper horns 

 on the females would not have been thus obliterated. 



The cases hitherto given refer to the Lamellicorns, but the males 

 of some few other beetles, belonging to two widely distinct groups, 

 namely, the Curculionidse and Staphylinidae, are furnished with 

 horns — in the former on the lower surface of the body," in the 

 latter on the upper surface of the head and thorax. In the Staphy- 

 linidae, the horns of the males are extraordinarily variable in the 

 same species, just as we have seen with the Lamellicorns. In 

 Siagonium we have a case of dimorphism, for the males can be 

 divided into two sets, differing greatly in the size of their bodfes 

 and in the development of their horns, without intermediate 

 gradations. In a species of Bledius (fig. 23), also belonging to the 



Fig. 23. Bledius taurus, magnified. Left-hand figure, male; right- 

 hand figure, female. 



Staphylinidae, Professor Westwood states that, "male specimens 

 "can be found in the same locality in which the central horn of 

 "the thorax is very large, but the horns of the head quite rudi- 

 "mental; and others, in which the thoracic horn is much shorter, 

 "whilst the protuberances on the head are long.'"" Here we ap- 

 parently have a case of compensation, which throws light on that 

 just given of the supposed loss of the upper horns by the males of 

 Onitis. 



Law of Battle. —Some male beetles, which seem ill-fitted for 

 fighting, nevertheless engage in conflicts for the possession of the 

 females. Mr. Wallace''' saw two males of Leptorhynchus angusta- 



»' KIrby and Spence, 'Introduot. Entomolog.' vol. iii. p. 329. 



«' 'Modern Classification of Insects,' vol. i. p. 172: Siagonium, p. 172. 

 In the British Museum I noticed one male specimen of Siagonium in 

 an intermediate condition, so that the dimorphism is not strict. 



" "The Malay Archipelago,' vol. ii. 1869, p. 276. Riley, Sixth 'Re- 

 port on insects of Missouri,' 1S74, p. 115. 



