PROTECTIVE RESEMBLANCE 139 



That many caterpillars, and the chrysalides of some 

 butterflies, possess a limited power of adjusting their 

 colours to suit their surroundings is beyond question. 

 Professor Poulton obtained a large batch of eggs laid 

 by one peppered moth (Amphydasis betularia) and divided 

 them into two parts. One half of the larvae were reared 

 among green leaves and shoots exclusively, and became 

 bright green without exception. The other larvae were 

 supplied with leaves growing upon dark brown twigs, and 

 in nearly all cases they became dark brown, though 

 about one or two per cent, took their colour from the 

 leaves. More recently it has been found that the greenish 

 or grey lichen-like marks which characterise certain 

 caterpillars are influenced by the environment of the 

 individual. When caterpillars of the scalloped hazel 

 moth {Odontoptera bidentata) feed among lichen-covered 

 twigs they develop the lichen-like patches, while those 

 whose lot is cast among twigs on which no lichen is 

 growing do not. Similar results have attended experi- 

 ments with the large caterpillars of the lappet moth 

 {Gastropacha quercifolia). Effects such as these are 

 believed to be due to the stimulus of reflected light upon 

 the nerve-endings in the skin. The change takes place 

 slowly, and can only be accomplished two or three times 

 in the lifetime of a caterpillar ; while we shall see that 

 the colour of the chrysalis is predetermined by the 

 surroundings of the caterpillar prior to its final moult. 

 Yet, as Professor Poulton has said, this is sufficient, for 

 caterpillars wander but little during their period of growth, 

 while chrysalides cannot wander at all. 



In the case of the small tortoiseshell butterfly ( Vanessa 

 urticce), Professor Poulton proved that the surroundings 

 of the full-fed caterpillar determined the colour of the 

 chrysalis. Briefly, a black environment gave rise to dark 



