VARIABLE PEOTECTIVE KESEMBLANCE IN INSECTS 147 



the colour of the caterpillars may vary according to 

 the colour of the plant upon which they are found. 

 This is especially true of caterpillars feeding upon 

 brightly coloured parts of the plant, such as the 

 anthers or petals. At the same time there has been, 

 until recent years, hardly any systematic investigation 

 of these interesting facts. Professor E. Meldola's 

 editorial notes to his translation of Dr. Weismann's 

 ' Studies in the Theory of Descent ' (the essay on 

 ' The Origin of the Markings of Caterpillars ') contain 

 many instances of this kind, together with most sug- 

 gestive remarks upon them, which first induced me to 

 work at the subject. At a still earlier date the same 

 writer had brought together all the scattered examples 

 of this kind, including the power of adjusting the 

 colours of pupae, and had drawn attention to the 

 general principles involved. 1 



Experiments upon the larva of the Eyed Hawk Moth 



(Smerinthus ocellatus) 



The instance which Professor Meldola chiefly con- 

 siders in his editorial notes is that of the caterpillar 

 of the Eyed Hawk Moth (Smerinthus ocellatus), which 

 is of a whitish-green colour when it is found upon 

 apple and certain kinds of willow, and of a bright 

 yellowish-green when found upon other species or 

 varieties of willow. ' The colours are on the whole 



1 Proc. Zool. Soc. 1873, p. 153. 



