372 TROPICAL NATURE 



ghost-moth may render it more easily seen by the female 

 while flying about in the dusk ; and if to this we add that it 

 will be also more readily distinguished from allied species, we 

 have a reason for diverse ornamentation in these insects quite 

 sufficient to account for most of the facts, without believing 

 in the selection of brilliant males by the females, for which 

 there is not a particle of evidence. 1 



Probable use of the Horns of Beetles 



A somewhat analogous case is furnished by the immense 

 horns of some beetles of the families Copridae and Dynastidse, 

 which Mr. Darwin admits are not used for fighting, and there- 

 fore concludes are ornaments, developed through selection of 

 the larger -horned males by the females. But it has been 

 overlooked that these horns may be protective. The males 

 probably fly about most, as is usually the case with male 

 insects ; and as they generally fly at dusk they are subject to 

 the attacks of large-mouthed goatsuckers and podargi, as well 

 as of insect -eating owls. Now the long, pointed, or forked 

 horns, often divergent, or movable with the head, would 

 render it very difficult for these birds to swallow such insects, 

 and would therefore be an efficient protection, just as are the 

 hooked spines of some stingless ants and the excessively hard 

 integuments of many beetles, against the smaller insectivorous 

 birds. 



Cause of the greater Brilliancy of some Female Insects 

 The facts given by Mr. Darwin to show that butterflies 

 and other insects can distinguish colours and are attracted by 

 colours similar to their own, are quite consistent with the 

 view that colour, which continually tends to appear, is utilised 

 for purposes of identification and distinction when not required 

 to be modified or suppressed for the purpose of protection. 

 The cases of the females of some species of Thecla, Callidryas, 

 Colias, and Hipparchia, which have more conspicuous mark- 

 ings than the male, may be due to several causes : to obtain 

 greater distinction from other species ; for protection from 

 birds, as in the case of the yellow-underwing moths; while 

 sometimes as in Hipparchia the lower intensity of colour- 

 1 See M. Fabre's testimony on this point, Descent of Man, p. 291. 



