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Show 270 DARWINISM t:UAl'. ~ 11 d much less protectively formed and coloured. IS sma, er an . . h . 1 th t In the bees and wasps (Hymenoptera) It IS also t c Ill e a h l'lre I·rl colour though there are sevcraJ cases t c sexes are a 1 .... ' 1 b · amono- solitary bees where they differ; the fema e . eu~g bl 1 band the male brown in Anthophora, rctus<::t., while m A~~l;~na fulva the female is more brightly coloured than the male. Of the great order of beetles _(Coleoptera) th_c sa~c h . b ·cl Though often so riCh :.tnd vaned m thmr t mo- may c s:11 . . colo~rs the sexes arc usually alike, and_ Mr. Darwm wa,s on 1y able to find about a dozen cases in whiCh there :w~s any conspicuous difference between them.I They exh1b1t, however, nun1erous scxu.."., l ch"••r ".-ctc1·s , in the lenbo-th of the an. tenn~, am.l · h . lco·s or· ). aws remarkably enhtrged or curiously mo<h- In Oll1S, 0 , • fied in the male sex. It is in the family of dragonflies (order ~ ~uropter:t) that we first meet with numerous ca,ses of <hstmctlvc cxual coloration. In some of the Agrioniclre _the males have the bodies rich blue and the wings black, while the fem<tles have the bodies green and the wings transparent. In the North American genus Hctrerina_ the mal~s alone have a cttrmine spot at the base of each wmg ; but m some other genera the sexes hardly differ at all. . . . The o-reat order of Lepidoptera, mcludwg the butterfhc~'> aJHl moths ~ffords us the most numerous and triking ex<unple of diver ity of sexual colouring. Amo~g the. moth. the ~liffcrcncc is usually but slight, being ma~Ifested 111 a greu,t~r mtcnsity of the colom of the sm~l~er. wmged ~ale; but m a few cases there is a decided difference, as 111 the gho. t-moth (Hepialus humuli), in which the male ~s pure w~ite, while the female is yellow with darker mark111gs. Th~ s may. he :1. recognition colour, enabling the female more readily to d1scowr her mate· and this view receives some support from the hd that in the Shetland Islands the male is almost as yellow as the female since it has been suggested that at midsummer, when this ~oth appears, there is in that high latitude ufficient twilight all night to render any special coloration unncces-sary. 2 Butterflies present us with a wonderful amount of scxu.tl 1 Darwin's Descent of Man, p. 294, and footnote. 2 Nature, 1871, p. 489. x COLOURS AND ORNAME TS CHARACTERISTIC OF SEX 271 difference of colour, in many cases so remarkable that the two s~xes of the same :pecies remained for many years under differ~nt names and were thought to be quite distinct species. vVe find, h?we~er, every gradation from perfect identity to complete chve_rsit:>:, and in some ct~.ses we are able to sec a reason for this difference. BeO'inninu with the n1ost t · _ d . f . . b b ex ra or m~ry cases o diversity-a~ in Diadema misippus, where the m~le IS bl~tck, or~am~nted w1th a large white spot on each wmg margmed \~Ith nch changeable blue, while the female is orange-~row~ with black spots and stripes-we find the expla~1at10n m the fact that the female mimics an uneatable Danais, and thus gains protection while layina it. cO'gs on low pl~nts in co_mpany with that insect. In the alli~d species, Dmdema bolma, the females arc also very different from the males, b~t are of dusky ?rown tint , evidently protective and very varmble, orne specimens having a general resemblance to t~e uneatable Euplreas ; so that we see here some of the e~rher stag~s of both forms of protection. The remarkable differ~ncos 111 some South American Pieridre are similarly explamed. The males of Pieris pyrrha, P. Jorena, and several_others, are white with a few black bands and marO'inal sp?ts hke so many of their allies, while the femalcsb are ga1ly colo~red with yellow and brown, and exactly re emlle s~me_ speci?s . of th~ uneatable Heliconiclre of the . arne d1stn~t. Similarly, m _the Malay Archipelago, the female of DI~dema anomala Is glossy metallic blue, while the male IS. brown ; the reason for this reversal of the usual rule ~emg, that the female exactly mimics the brilliant colourmg of the comm~n and uneatable Euph:ea midamus, and t~us secure~ protectiOn. In the fine Adolias dirtea, the male _IS black with ~ few specks of ochre-yellow and a broad ~argmal_band of nch metallic greenish-blue, while the female IS browms~-black entirely covered with rows of ochre-yellow spots. Thi~ latter. coloration does not appear to be protective when the msect Is seen in the cabinet, but it really is so. ! have observed the female _of this butterfly in Sumatra, where It settles ?n th~ ground m the forest, and its yellow pots so harmomse w1th the flickering gleams of sunliaht on the d~ad leaves that it can ouly be detected with the greatest difficulty. |