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78 NATURAL SELECTION insame district, whereas allied forms of every degree of nearnessand remoteness generallyinhabit different countries, andoften different quarters of the globe and;neither it nor"similar conditions" will account for the likeness betweenspecies of distinct groups being superficial only a disguise,not a true resemblance ;for the imitation of bark, of leaves,of sticks, of dung ;for the resemblance between species indifferent orders, and even different classes and sub-kingdoms ;and finally, for the graduated series of the phenomena,beginning with a general harmony and adaptation of tint inautumn and winter moths and in arctic and desert animals,and ending with those complete cases of detailed mimicrywhich not only deceive predacious animals, but puzzle themost experienced insect collectors and the most learnedentomologists.Mimicry by Female Insects onlyBut there is yet another series of phenomena connectedwith this subject, which considerably strengthens the viewhere adopted, while it seems quite incompatible with eitherof the other hypotheses; namely, the relation of protectivecolouring and mimicry to the sexual differences of animals.It will be clear to every one that if two animals, which asregards " external conditions " and " hereditary descent " areexactly alike, yet differ remarkably in coloration, oneresembling a protected species and the other not, the resemblancethat exists in one only can hardly be imputed to theinfluence of external conditions or as the effect of heredity.And if, further, it can be proved that the one requiresprotection more than the other, and that in several cases it isthat one which mimics the protected species, while the onethat least requires protection never does so, it will affordvery strong corroborative evidence that there is a real connectionbetween the necessity for protection and the phenomenonof mimicry. Now the sexes of insects offer us a testof the nature here indicated, and appear to furnish one ofthe most conclusive arguments in favour of the theory thatthe phenomena termed " mimicry " are produced by naturalselection.The comparative importance of the sexes varies much in