COLORATION AFFECTED BY THE ENVIRONMENT. 43 



characters which distinguish the two sexes. Normally the 

 male insect has the upper surface of the wings of a shining 

 white colour, while in the female they are brown. In the 

 Shetland Islands, but not in the Hebrides, a proportion of the 

 males captured were like the females. 



The same naturalist noted a tendency in a number of species 

 of Geometrides * taken in the Hebrides towards'a greyer colora- 

 tion than the normal ; but it is suggested that this is clue to 

 the prevalent grey gneiss ; by natural selection only those 

 forms which approached the gneiss in colour were preserved. 

 A similar explanation has been given of the black Lizard 

 (Lacerta Ximoti'ji) found on an island of the Canary group ; it 

 does not greatly differ, except in coloration, from Lacerta 

 ocellata ; it is said that the black colour renders it less con- 

 spicuous to predaceous birds, which are its only enemies, since 

 the rocks upon which the animal lives are very dark in colour. 

 On the other hand, this black colour may be referable to the 

 same causes uanielv, moisture, which Eimer thinks have been 



v J 



effectual in the case of certain melanic varieties of lizards in 

 the Mediterranean islands. 



A large moth, Bombyx tnfolii, appears, from the observations 

 of Mr. Milfordj to have a distinct local variety in Romney 

 Marsh, Kent ; it is paler than the normal insect. The larvae 

 were first found by Mr. Milford, " in May 1866, feeding in the 

 tufts of a very wiry grass growing in the shingle above high- 

 water mark ; they were again found and bred in May 1876. 

 In August 1868 two dead moths, exactly similar, were 

 observed in the same locality ; and in August 1871 eighteen 



* Entomologist, 1881, p. 220. The following are the species : 

 repandata, DasyiHa obfuscata, Larentia dhlyuiatu, L. wsidtu, 

 russata, Melanippe haxtatu, J/. ntuntanata. 



f Entomologist, vol. vi., p. 53. 



