INSECTS. 337 



two sexes in above a hundred species of the Copridoe, did 

 not tind any marked difference in this respect among well- 

 developed individuals. In Lethrus, moreover, a beetle 

 belonging to the same great division of the Lamellicoms, 

 the males are known to fight, but are not provided with 

 horns, though their mandibles are much larger than those of 

 the female. 



The conclusion that the horns have been acquired as 

 ornaments is that which best agrees with the fact of their 

 having been so immensely, yet not fixedly, developed as 

 shown by their extreme variability in the same species, and 

 by their extreme diversity in closely-allied species. This 

 view will at first appear extremely improbable; but we shall 



Figr. 21. Fig. 22. 



Fig. 21. Onitis furcifer, male viewed from beneath. 



Fig. 22. Left-hand figure, male of Onitis furcifer, viewed laterally. Right- 

 hand figure, female, a. Rudiment of cephalic horn. b. Trace of 

 thoracic horn or crest. 



hereafter find with many animals standing much higher in 

 the scale, namely fishes, amphibians, reptiles and birds, 

 that various kinds of crests, knobs, horns and combs have 

 been developed apparently for this sole purpose. 



The males of Onith furcifer (fig. 21), and of some other 

 species of the genus are furnished with singular projections 

 on their anterior femora, and with a great fork or pair of 

 horns on the lower surface of the thorax. Judging from 

 other insects, these may aid the male in clinging to the 

 female. Although the males have not even a trace of a horn 

 on the upper surface of the body, yet the females plainlv ex- 

 hibit a rudiment of a single horn on the head (fig. 22, a) and 

 of a crest {h) on the thorax. That the slight thoracic crest 

 in the female is a rudiment of a projection proper to the male, 

 though entirely absent in the male of this particular species, 

 is cl^ar; for the female of Bubas. bison (a genus which 



