VARIABLE PROTECTIVE RESEMBLANCE IN INSECTS 149 



the direct chemical effect of different kinds of leaves 

 upon them after being eaten, and it was therefore 

 called phytophagic variability. Many special experi- 

 ments were directed toward the solution of this 

 question. Thus, leaves were sewn together, so that 

 the caterpillars were exposed to the colour of the 

 upper or of the under side alone, although they ate 

 the same leaf in both cases. In other instances the 

 ' bloom ' was rubbed off the under sides of some leaves 

 (Salix fragilis, incorrectly described as Triandra in 

 my papers) , while others were left normal. The results 

 proved that the caterpillars are affected by the colour 

 of the leaves and not by the leaves as food. Com- 

 parison with the experiments on pupae renders it 

 most probable that reflected light influences the skin. 



Experiments upon the larvae of other Sphingidse 



Professor Meldola had also quoted the instance of 

 the larva of the Privet Hawk Moth (Sphinx ligustri), 

 which is of a much brighter green when found upon 

 privet than when found upon lilac. Larvae of this 

 species, from the same batch of eggs, were fed upon 

 the two plants, and the above quoted observation 

 was confirmed. The larvae of the Lime Hawk Moth 

 (Smerinthus tilice) were similarly modified, being made 

 unusually light green by the use of variegated elm 

 and a lime having leaves with very white and downy 

 under sides. 



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