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Show 394 SEXUAL SELECTION. PART II. male, and slightly different in some other respects. In an allied Indian form, the Iphias glaucippe, th~ oran~etips are fully developed in both sexes. In th1s Iph1as the under surface of the wings marvellously resembles, as pointed out to me by Mr. A. Butler, a pale-coloured leaf; and in our English orange-tip, the under surf~ce resembles the flower-head of the wild parsley, on whiCh it may be seen going to rest at night.~ The same reasoning power which compels us to beheve that the lower surfaces have here been coloured for the sake of protection, leads us to deny that the ;vings have been tipped, especially when this character IS confined to the males, with bright orange for the same purpose. TurninG" now to Moths: most of these rest motionless with 0 their wings depressed during the whole or greater part of the day; and the upper.surfaces of. their wings are often shaded and coloured m an adm1ra~le manner, as Mr. Vvallace has remarked, for escapmg detection. "\Vith most of the Bombycidre and Noctuidre, 7 when at rest, the front-wings overlap and .{;onceal the hind-wings; so that the latter might be brightly coloured without muc~ risk; and ~~ey are thus coloured in many speCies of both fam1hes. During the act of flight, moths would often be able to escape from their enemies; nevertheless, as the hind-wings are then fully exposed to view, their bright colours must generally have been acquired at the cost of some little risk. But the following fact shews us how cautious we ouaht to be in drawing conclu- o . sions on this head. The common yellow under-wmgs fi See the interes1ing observations by Mr. T. W. Wood, 'The Stu~ <lent,' Sept. 1868, p. 81. i Mr. Wallace in • Hardwicke's Science Gossip,' Sept. 1867, p. 193. CHAP. XI. BUTTERFLIES AND MOTHS. 395 (Triphaena) often fly about during the day or early evening, and are then conspicuous from the colour of -their hind-wings. It would naturally be thought that this would be a source of danger ; but Mr. J. Jenner Weir believes that it actually serves them as a means {)f escape, for birds strike at these brightly coloured and fragile surfaces, instead of at the body. For instance, 1\ir. Weir turned into his aviary a vigorous specimen of Triphaena pronuba, which was instantly pursued by a robin; but the bird's attention being caugQ.t by the coloured wings, the moth was not captured until after about fifty attempts, and small portions of the wings were repeatedly broken off. He tried the same experiment, in the open air, with a T. fimbria and swallow; but the large size of this moth probably interfered with its capture.8 We are thus reminded of a statement made by Mr. 'Vallace,9 namely, that in the Brazilian forests and Malayan islands, many common and highly-decorated butterflies are weak flyers, though furnished with a broad expanse of wings ; and they "are ~' often captured with pierced and broken wings, as if •: they had been seized by birds, from which they had "escaped: if the wings had been much smaller in pro" portion to the body, it seems probable that the insect "would more frequently have been struck or pierced in "a vital part, and thus the increased expanse of the ''wings may have been indirectly beneficial." Display.-Tbe bright colours of butterflies and of some moths are specially arranged for display, whether Ql' not they serve in addition as a protection. Bright 8 See also, on this subject, Mr. W cir's paper in ' Transact. Ent. Soc.' 18G9, p. 23. 9 ' Westminster Review,' July, 1867, p. 1G. |