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Show 266 DARWINISM CHAP. to have acquired the power of feeding on co:als and m~dus~; and the beautiful bands and spots and br1g~t colours w~th which they are frequently adorned, may be e1ther pr?tect1vc when feedin()' in the submarine coral groves, or may, m some cases, be wa~ning colours to show that they themselves arc poi. onous and uneatable. . . . . A remarkable illustration of the Wide extensiOn of warmng colours and their very definite purpose in nature, is afforded by wha' t may now be termed "Mr. Be I t 's f rog. " F rogs m. al l parts of the world arc, usually, protectively co]?ured with greens or browns · and the little tree-frogs are mther green like the leaves th~y rest upon, or curiously mottled to imitat bark or dead leaves. But there are a certain number of very gaily coloured frogs, and these do not conceal themselves as fro()'s usually do. Such was the small toad found by Darwin at Bahia Blanca, which was intense black and bright vermilion, and crawled about in the sunshine over dry sand-hills and arid plains. And in Nicaragua, Mr. Belt found a little frog goraeously dressed in a livery of red and blue, which did not 0 attempt concealment and was very abundant, a combination of characters which convinced him that it was uneatable. He, therefore, took a few specimens home with him and gave them to his fowls and ducks, but none would touch them. At last, by throwing down pieces of meat, for which there was a great competition among the poultry, he managed to entice a young duck into snatching np one of the little frogs. Instead of swallowing it, however, the duck instantly threw it out of its mouth, and weu t. about jerking its head as if trying to get rid of some UJIplen- sant taste.1 The power of predicting what will happen in a given cnRc is always considered to be a crucial test of a true theory, and if so, the theory of warning colours, and with it that of mimicry, must be held to be well established. Among tho creatures which probably have warning colours as a . ign of ineclibility arc, the brilliantly coloured nudibranchiate mollu. cs, those curious annelids the N creis and the Aphrodite or seamouse, and many other marine animals. The brilliant colours of the. callops (Pecten)and some other bivalve shells are perhaps 1 The Nat1walist in Nicaragua, p. 321. IX WARNING COLORATION AND MIMICRY 267 an indication of their hardness and consequent inedihility; as in the case of the hard beetles; and it is not impr·obn.blc that some of the pho phorcscent fishes and other marine organisms may, like the glow-worm, hold out their lamp as a warnina to cncmics.1 In Queensland there is an exceedingly poison~us spider, whose bite will kill a doer, and can c . evcrc illness with excruciating pa~n in man. It i. black, with a bright vermilion patch on the 1mddle of the body; and it i · so well rccoani ·ed by this conspicuous coloration that even the spider-h~ntin(•' wasps a, void it. 2 0 Locn:ts ancl grasshoppers arc generally of green protective tint , hut there arc many tropical species most ga,uclily decorated with red, blue, a,ncl hla.ck colours. On the same general ground. as those hy which Mr. Belt predicted the incdihllity of hi. conspicnou frog, we miO'ht safely predict the same for these insects; but we have fortunately a proof that they arc so protected, since Mr. Charles Horne tate that one of the brio·ht coloured Indian locusts was invariably rejected when offered to birds :mel lizards. 3 The examples now given lead ns to the conclusion that colours a~quired for the purpose of erving as a danger-signal to enenuc are very wide. preacl in nature, and, with the corresponding colour of the pecies which mimic them, furnish us with a rational explanation of a, considerable portion of the coloration of animals which is outside the limits of those colours that !}ave been acquired for either protection or recognition. There remains, however, another set of colours, chiefly among the higher animals, which, being connected with some of the mo t interesting and most disputed questions in natural history, must be discus. ed in a separate chapter. 1 Mr. Belt first suggested this use of the light of the Lampyrid::e (fireflies and rrJow-wonn ·) -.Nat11mlist in Nimmgua, p. 320. Mr. Verrill and Professor Meldola made the same suggestion in the case of me1lns::e anu other phosphorescent marine orgaui. r11s (Natnre, vol. xxx. pp. 281, 289). 2 W. E. Armit, in Natun, vol. xviii. p. 642. 3 Proc. Ent. Soc., 1869, p. xiii. |