VARIABLE PROTECTIVE RESEMBLANCE IN INSECTS 129 



other position, for the pupse from both sets of larvae 

 were identical. 



I was thus driven to the conclusion that the 

 general surface of the skin of the caterpillar is sensi- 

 tive to colour during stage ii. and part of stage iii. 

 In order to test this conclusion I wished to subject 

 the body of the same larva to two conflicting colours, 

 such as black and gold, producing the most opposite 

 effects upon the pupa. Such an experiment, if 

 successfully carried out, would decide some important 

 points. If the part of the body containing the head 

 was not more sensitive than the other part, a valuable 

 confirmation of the blinding experiments would be 

 afforded. Mrs. Barber's suggestion that parti- coloured 

 pupae may be produced by the influence of two colours 

 would be tested in a very complete manner ; if parti- 

 coloured pupae were obtained it seemed probable that 

 the light acts directly upon the skin, but if they could 

 not be obtained it seemed more probable that the 

 light influences the termination of nerves in the skin, 

 and that the pupal colours are produced through the 

 medium of the nervous system. 



The practical difficulties in the way of such an ex- 

 periment were very great, for the conflicting colours 

 could only be applied during stage iii., when the larva 

 is motionless and may be disturbed with impunity. 

 If, on the other hand, a larva be disturbed in stage 

 ii. it begins to walk about and thus renders the 

 experiment impossible. The only way to obtain 



