232 ROMANCE OF THE INSECT WORLD CHAP. 



alter its appearance in order to adapt itself to 

 surroundings, due to natural selection, which seizes 

 upon and renders definite variations which are of 

 service to the species. In Variable Protective Re- 

 semblance, about to be described, each particular 

 individual is capable of adapting itself, of altering its 

 form, to bring it into consonance, and therefore 

 protection, with the various conditions that it is likely 

 to meet with in Nature. Of the two kinds of 

 dimorphism, clearly that where individual suscepti- 

 bility is present is of far higher protective value. 



It is now a quarter of a century ago since Mr. T. 

 W. Wood, in a paper read before the Entomological 

 Society of London, stated as the result of observations 

 that the pupae of certain Lepidoptera corresponded in 

 colour to their surroundings. The " Garden Whites " 

 he had found to be dark on tarred fences and in sub- 

 dued light, while these pupae were light-coloured when 

 attached to light surfaces. In the same way the 

 chrysalis of the Large Tortoiseshell Butterfly ( Vanessa 

 bolyckloros) was coloured like a withered leaf when 

 suspended among foliage. It was then light reddish- 

 brown with metallic silvery spots, while a specimen 

 from a wall was mottled gray and the metallic spots 

 were not produced. Between 1867, the date of these 

 announcements, and the present day, the experiments 

 of various observers have confirmed the truth of the 

 general principle involved in Mr. Wood's researches. 

 By exposure of pupae of Lepidoptera to different 

 surfaces, it has been proved beyond doubt that many 

 possess the power of adjusting their colours to the 

 normal surfaces to which they are fixed (see Figs. 44 



