Local Colour-Variation in Lizards

Abstract

MR. HENRY HILLYER GIGLIOLI remarks (NATURE, vol. xix. p. 97) that the common lizard (Podarcis muralis) constantly presents dark varieties on islets adjoining small islands. A similar case has come under my observation in the herpetological fauna of this country. Ameiva (cnemidophorus) vulgaris, Licht., is very common all over Venezuela, and though it varies consider ably in colour, it is, on the mainland, never black, as on the small islands of Los Roques and Orchila, which lie a short distance off our Caribbean coast. Both islands have rather extensive sandy beaches, covered with a very scanty vegetation, so that, mutatis mutandis, they are, in the very words Mr. Giglioli uses when speaking of Filfla, painfully white in the glaring tropical sun, the black lizards being therefore most conspicuous. Prof. Peters, of Berlin, to whom some years ago I sent specimens of these reptiles, called them in one of his letters Cnemidophorus nigricolor, but as I am not aware of his having published this name, I believe he got soon convinced of its true character as a melanotic variety. I may be allowed to add that I have mentioned this case already in my “Estudios sobre la Flora y Fauna de Venezuela” (Caracas, 1877), pp. 280, 281, when I also pointed out the difficulty of its explanation by the “struggle for existence” theory.