PDF - Wallace Online

NATURAL SELECTIONbutterfly, Papilio paradoxa. I have since named thisinteresting species Diadema anomala (see the Transactions ofthe Entomological Society, 1869, p. 285). In this case, andin that of Diadema misippus, there is no difference in thehabits of the two sexes, which fly in similar localities ;so thatthe influence of " external conditions " cannot be invokedhere as it has been in the case of the South American Pierispyrrha and allies, where the white males frequent opensunny places, while the Heliconia-like females haunt theshades of the forest.We may impute to the same general cause (the greaterneed of protection for the female, owing to her weaker flight,greater exposure to attack, and supreme importance) thefact of the colours of female insects being so very generallyduller and less conspicuous than those of the other sex.that it is chiefly due to this cause rather than to what Mr.Darwin terms " sexual selection " appears to be shown by theotherwise inexplicable fact, that in the groups which have aprotection of any kind independent of concealment, sexualdifferences of colour are either quite wanting or slightlydeveloped. The Heliconidae and Danaidae, protected by adisagreeable flavour, have the females as bright and conspicuousas the males, and very rarely differing at all fromthem. The stinging Hymenoptera have the two sexes equallywell coloured. The Carabidse, the Coccinellidae, Chrysomelidse,and the Telephori have both sexes equally conspicuous, andseldom differing in colours. The brilliant Curculios, whichare protected by their hardness, are brilliant in both sexes.Lastly, the glittering Cetoniadae and Buprestidae, which seemto be protected by their hard and polished coats, their rapidmotions and peculiar habits, present few sexual differencesof colour, while sexual selection has often manifested itselfby structural differences, such as horns, spines,processes.Cause of the dull Colours of Female Birdsor otherThe same law manifests itself in Birds. The female whilesitting on her eggs requires protection by concealment to amuch greater extent than the male ;and we accordingly findthat in a large majority of the cases in which the male birds