XV 



them more highly developed in nocturnal species than in their nearest 

 diurnal allies ; in monophagous groups — especially if their food be rare or 

 somewhat difficult to discover — than in such as are polyphagous ; and 

 in the sluggish species than in such as are eminent for their locomotive 

 povyers. 



" The sexual differences in the mandibles and legs need scarcely occupy 

 our attention, since in a very large number of cases their functions have 

 been traced beyond room for doubt, and it is admitted that male insects 

 in which these parts are pre-eminently developed must have an advantage 

 over such as are less highly endowed, and must have a greater chance 

 of leaving a numerous progeny. It has doubtless been remarked how 

 completely the anterior legs of Eucheirus simulate the mandibles of 

 Lucanus. 



" But it is with the sexual developments of the thorax and of the 

 fixed parts of the head that we must mainly concern ourselves, as 

 they are still an unsolved riddle. Naturalists of the new school can 

 scarcely sit down in content and regard the thoracic horns — e.g., of the 

 DynastidcB or ScaraheBidcB — as mere lusus natural, or as existing simply 

 to excite the wonder and curiosity of man. Are they weapons ? Their 

 shape, their position, the sparing mobility of the parts to which they 

 are attached, and the general difficulty with which they could be brought to 

 bear upon an enemy are strongly opposed to this supposition. Though 

 popularly known as ' horns,' they offer in all these respects a decided 

 contrast to the horns of the Mammalia, which are formidable just in 

 proportion as the head of the animal bearing them is capable of rapid and 

 powerful motion. 



''Let us take certain extreme cases: in several African and Indian 

 Onthophagi, such as O.rarus, pyramidaUs, amplecticornis, EUiotti, bonassus, 

 hippelaphus and iinperator, a pair of processes almost like calliper compasses 

 spring from the angles of the occiput and extend backwards over, and in 

 one case lying flat upon, the thorax and elytra. Or, again, Peperonata 

 Haringtonl, which has its thorax prolonged behind in the form of a liook 

 with the point downwards, by which the insect could easily be suspended. 

 Anything worse adapted for weapons could not easily be devised. 



" But further, male insects fitted with these so-called horns, have never 

 been seen to use them in fighting, whether with rivals or with enemies of 

 other species. Our worthy President, Mr. Bates, who has examined several 

 species of horned Coleop)tera, finds no decided evidence, from their mutilated 

 or broken condition, of their having been thus used. I have seen many 

 hundred living specimens of Oryctes nasicornis in heaps of spent tan, and 

 have repeatedly and carefully watched their proceedings. But I never saw 

 the horns used as weapons. Indeed I have no note of ever having witnessed 

 a fight between two males of this species. 



