iv INFLUENCE OF FOOD ON COLOUR 151 



sativa or Atropa belladonna, not one of the imagines pro- 

 duced resembles the original form; when the insects have 

 been fed on lettuce the white ground-colour of the wings 

 predominates ; when fed on deadly nightshade the brown 

 markings of the upper wings often coalesce and the white 

 vanishes ; in like manner the blue markings on the lower 

 wings fuse together and displace the orange-yellow ground 

 colour. To which I may add, that according to Koch's work, 

 The Lepidoptera of South- West Germany, feeding with bella- 

 donna and poppies produces dark-coloured imagines. Koch 

 made experiments with similar results on Chelonia plantaginis 

 and Gastropacha pini. Finally, he refers to experiments with 

 similar results on species of Militaea and Argynnis, as already 

 known. 



"Must not," concludes Koch, "similar processes occur 

 equally, and even on a larger scale, in the natural life of the 

 countless forms of the class in question? When a great 

 number of individuals perish through an occasional scarcity 

 of their proper food-plant, must not nevertheless considerable 

 numbers survive by contenting themselves with other allied 

 food materials, and so give rise to varieties whose origin we 

 do not dream of, and which therefore we are led to regard as 

 new species?" 



Further, he brings forward instances to show that cold 

 or warmth, moisture or dryness of climate, change the size 

 and colouring of Lepidoptera. 



Thus the chess-board butterfly (Arge Galathea) in middle 

 Germany is quite different in appearance from its dark varieties 

 (Procida and Leucomelas) which occur in the Tyrol and the 

 southern parts of Europe ; the speedwell butterfly (Melitsea 

 Artemis) in middle Germany is always smaller and duller 

 coloured than its highly coloured varieties (Desfontainesi and 

 Beckeri) in Spain. Our buckthorn butterfly (Gonopteryx 

 rhamni) acquires in Southern Italy and Portugal a large 



