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Show CIIAP. 272 DARWINISM. A hundred other cases might be quoted in which the :iemalc i. either more obscurely coloured than .the male, or gains protection by imitating some inedible specw~; and any one who has watched these female insects flymg. slowly alon<r in search of the 1_)lants on which to deposit their errrrsb will understand how important it must be to them n~t 'to attract the attention of insect- eating birds by too conspicuous colours. The number of b.ird. w~ich cap~urc insect. on the wing is much greater m tropiCal regwns than in Europe; and this is perhaps the rcaso~1 wh;y many of our showy species are alike, or almost ahkc, m both sexes, while they arc protectively coloured 011 the under side which is exposed to view when they·m~c at rest. . Such a.rc our peacock, tortoise-shell, and red admiral buttorfhcs; while in the tropics we more commonly find that the females arc less conspicuous 011 the upper surface even when protectively coloured beneath. We may here remark, that the cases already quoted prove clearly that either male or female may be modified in colour apart from tho opposite sex. In Pieris pyrrha a.nd its allies the male retains the usual type of coloration of the whole crenus, while the female has acquired :1 distinct and peculiar ~tylc of colouring. In Adolias dirtea, on the other band, the fema.le appears to retain something like the primitive colour and markings of the two sexes, modified perhaps for more perfect protection; while the ma.le ha.s acquired more and more intense a.nd brillia.nt colours, only showing his original markings by the few small yellow spots that remain ncu,r the base of the wings. In the more gaily coloured Pieridre, of which our ora.nge-tip butterfly may be taken as a type, we sec in the fema.le the plain ancestral colours of the group, while the maJe has acquired tho brilliant orange tip to its wings, proLably as a recognition mark In those species in which the under surface is protectively coloured, we often find the upper surface alike in both scxe:-;, the tint of colour being usually more intense in the ma.lc. But in some cases this leads to the female being more con picuom;, as in some of the Lycrenidre, where tho female is bright blue and the male of a blue so much deeper a.nd soberer in tint as to appear the less brilliantly coloured of the two. x COLOURS AND ORNAMENTS CHARACTERISTIC OF SEX 273 Probable Causes of these Colou1·s. In. tho production of these varied results there have probably been several ca.uscs at work There seems to be a constant tendency in the male of most animals-but ?spcci~lly of birds and insects-to develop more and more mtons1ty of colour, often culminating in brilliant metallic blncs or greens or the most splendid iridc cent hues; while, at tho .same time, natura.l selection is constantly at work, prcventmg the female from acquiring these same tints, or mo~ifying her. c?lo~rs in various directions to secure protcct~ on by. a?similatmg her to her surroundings, or hy producmg mnmcry of some protected form. At tho same time, the need for recognition must be satisfied ; and this seems to h::wo led to eli vcr.-itics of colour in allied specie , sometimes the female, sometimes the ma.le undcrgoirw the grea.tcst chango a.ccording as one or other could h~ modified with the greatest ca.sc, and so as to interfere least with the welfare of the race. Hence it is that sometimes tho males of allied species vary most, as in the different species of Epica.liu,; sometimes the females, as in the magnificent green species of Ornithoptera and the ".<:Eneas " group of Papilio. ~he importance of the two principles-the need of prot? ctwn and recognition--in modifying the comparative colora~ wn of tho sexes a.mong butterflies, is bca.utifully illustrated m the case of the groups which arc protected by their distasteful. ness, and whose females do not, therefore, need the protectiOn afforded by sober colours. In the groat families, Heliconidro and Acrreidre, we find that the t~o sexes are almost always alike; and, in the very fc~ exceptwns, t~at the fcma.lc, though differently, is uot lc ·:J ga1ly or less conspiCuously coloured. In the Danaidre the same general rule prevails, but the cases in which the male exhil its greater intensity of colour tha.n the fcmu,lc arc perhaps more numerous than m the other two families. There is however a, curious difference in this respect between the Oriental a;Hl the America.n groups of distasteful Papilios with warn in rr colours, both of which arc tho subjects of mimicry. In th~ Eastern groups-of which P. hector a.nd P. coon may be taken T |