XVI 



" It has been suggested that these horns may either prevent the insects 

 in question from falhng on their backs — a position well known to be very 

 embarrassing to beetles — or at least enable them more easily to regain their 

 feet. This might hold good with the Ontlioi)hagi above mentioned. But 

 the question then arises, why the males should be better provided in this 

 respect than the females ? 



" Are these horns mining tools ? In some species, such as TijphcBus 

 vulgaris, their structure and position favour this supposition, and the males 

 seem to take a part in the formation of the burrows for their eggs. But 

 in others the horns are very ill adapted for mining either into soil or 

 rotten wood. 



" A theory which has been recently put forward regards these projections 

 in common with all horns, tusks, crests, manes, tufts, &c., distinguishing 

 the male sex iiot merely in insects, but throughout the animal kingdom, as 

 mainly excrementitious products — as a channel through which Nature 

 relieves herself of superfluous matter. In female animals, it is contended, 

 any excess in nutriment is utilized in the formation of ova, but in the males 

 it is consumed in the production of the class of appendages which we are 

 considering. This view is, if I do not misunderstand him, to some extent 

 sanctioned even by Dr. Leconte, who speaks of ' Vegetative growth of the 

 organs of sense, indicated by pectinate or flabellate antennae, or excessive 

 length of the palpi' (Silliman's Jouru., 1867, xliv., p. 4S). It is also main- 

 tained, though not by Dr. Leconte, that these horns occur chiefly, if not 

 exclusively, among vegetable-feeders, inasmuch as ' their diet contains an 

 excess of saline matter in proportion to its other constituents.' We have 

 in this last suggestion a perfect complication of errors. Vegetable food, 

 and especially wood, is not richer but poorer in mineral salts than is animal 

 food, and as the frontal and thoracic horns of insects contain merely 6'06 

 per cent, of mineral matter, they would not ofi'er a convenient channel for 

 the removal of such substances from the system. 



" Further, there is no necessary connection between these secondary 

 sexual characters and any particular kind of diet. The Dynastida;, the 

 Lucanida, the Longicornes, and the Buprestidce agree very closely in their 

 diet, all feeding upon wood in various stages of decay. Yet while the male 

 Dynastida are, above all other insects, endowed with horns, and the 

 male Lucanida; with enlarged jaws, the male Longicornes have merely an 

 extension or occasional complication of the antennte, or sometimes of the 

 palpi, and the male Buprestidm are devoid of any of these secondary sexual 

 characteristics. 



" Further, parts of this nature are not invariably present in the male and 

 absent in the female. The growth of horns may be approximately equal in 

 both sexes. Thus, in Phanmis lancifer, the frontal horn is almost as well- 

 developed in the female as in the male. In certain species of Onitis the 



