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72 NATURAL SELECTION inthat reptiles furnish us with a very remarkable and instructivecase of true mimicryṀimicry among SnakesThere are in tropical America a number of venomoussnakes of the genus Elaps, which are ornamented with brilliantcolours disposed in a peculiar manner. The ground colour isgenerally bright red, on which are black bands of variouswidths and sometimes divided into two or three by yelloAvrings. Now, in the same country are found several genera ofharmless snakes, having no affinity whatever with the above,but coloured exactly the same. For example, the poisonousElaps fulvius often occurs in Guatemala with simple blackbands on a coral-red ground; and in the same country isfound the harmless snake Pliocerus equalis, coloured andbanded in identically the same manner. A variety of Elapscorallinus has the black bands narrowly bordered with yellowon the same red ground colour, and a harmless snake, Homalocraniumsemi-cinctum (Colubridae), has exactly the samemarkings, and both are found in Mexico. The deadly Elapslemniscatus has the black bands very broad, and each of themdivided into three by narrow yellow rings ;and this again isexactly copied by a harmless snake, Pliocerus elapoides, whichis found along with its model in Mexico.But, more remarkable still, there is in South America athird group of snakes, the genus Oxyrhopus (Scytalidse),doubtfully venomous, and having no immediate affinity witheither of the preceding, which has also the same curiousdistribution of colours, namely, variously disposed rings ofred, yellow, and black ;and there are some cases in whichspecies of all three of these groups similarly marked inhabitthe same district. For example, Elaps mipartitus has singleblack rings very close together. It inhabits the west side ofthe Andes, and in the same districts occur Pliocerus euryzonusand Oxyrhopus petolarius, which exactly copy itspattern. In Brazil Elaps lemniscatus is copied by Oxyrhopustrigeminus, both having black rings disposed in threes. InElaps hemiprichii the ground colour appears to be black, withalternations of two narrow yellow bands and a broader redone ;and of this pattern again we have an exact double in