80 
NATURAL SELECTION 
hi 
butterfly, Papilio paradoxa. I have since named this 
interesting species Diadema anomala (see the Transactions of 
the Entomological Society , 1869, p. 285). In this case, and 
in that of Diadema misippus, there is no difference in the 
habits of the two sexes, which fly in similar localities ■ so that 
the influence of “ external conditions ” cannot be invoked 
here as it has been in the case of the South American Pieris 
pyrrha and allies, where the white males frequent open 
sunny places, while the Heliconia-like females haunt the 
shades of the forest. 
We may impute to the same general cause (the greater 
need of protection for the female, owing to her weaker flight, 
greater exposure to attack, and supreme importance) — the 
fact of the colours of female insects being so very generally 
duller and less conspicuous than those of the other sex. And 
that it is chiefly due to this cause rather than to what Mr. 
Darwin terms “ sexual selection ” appears to be shown by the 
otherwise inexplicable fact, that in the groups which have a 
protection of any kind independent of concealment, sexual 
differences of colour are either quite wanting or slightly 
developed. The Heliconidas and Danaidse, protected by a 
disagreeable flavour, have the females as bright and con- 
spicuous as the males, and very rarely differing at all from 
them. The stinging Hymenoptera have the two sexes equally 
well coloured. The Carabidse, the Coccinellidse, Chrysomelidae, 
and the Telephori have both sexes equally conspicuous, and 
seldom differing in colours. The brilliant Curculios, which 
are protected by their hardness, are brilliant in both sexes. 
Lastly, the glittering Cetoniadse and Buprestidee, which seem 
to be protected by their hard and polished coats, their rapid 
motions and peculiar habits, present few sexual differences 
of colour, while sexual selection has often manifested itself 
by structural differences, such as horns, spines, or other 
processes. 
Cause of the dull Colours of Female Birds 
The same law manifests itself in Birds. The female while 
sitting on her eggs requires protection by concealment to a 
much greater extent than the male ; and we accordingly find 
that in a large majority of the cases in which the male birds 
