372 TROPICAL NATURE v 
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.} 
Probable use of the Horns of Beetles 
A somewhat analogous case is furnished by the immense 
horns of some beetles of the families Copride and Dynastide, 
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. 
