INTRODUCTORY. 23 



the deposition in the tissues of the insect of but slightly 

 altered chlorophyll. The brown colour of the young insect is 

 probably suggestive of a withered leaf, so that the change of 

 colour here is immaterial as far as concerns the protection of 

 the insect ; brown or green might be supposed to be equally 

 useful tints for a leaf-feeding and leaf-resembling insect. 



Many green caterpillars are of a faint green from the very 

 first, and the eggs from which they are hatched are also green; 

 this is the case with the Convolvulus and Privet Hawk moths ; 

 but the green of the larva becomes intensified directly it begins 

 to feed ; the colour is largely due to the contents of the 

 alimentary tract seen through the semi-transparent walls ; but 

 the blood also becomes rapidly green-coloured. 



The larvre of most Sphingidfe pass through a very varied 

 series of changes from the time when they first leave the egg 

 to the time when they assume the chrysalis state. These 

 colour-changes have been recently studied with great care by 

 Mr. Poulton, especially with regard to the Convolvulus and 

 Privet Hawk moths. 



The earliest complete observations upon the subject were, 

 however, published by Weismann.* In this work, referred to 

 in the foot-note, the reader will find an abundance of detail in 

 addition to that selected for the present purpose. 



The caterpillar of the Large Elephant Hawk moth 

 ( Chcerocampa elpenor) leaves the egg with a yellowish-white 

 coloration, quite uniform, except for the caudal horn, which is 

 black ; later on the skin, at first transparent, becomes green, 

 the coloration being here, too, perfectly uniform, with the 

 exception of the caudal horn, which retains its dark, black 

 colour. 



After the first moult a fine white line on either side extended 



* " Studies in the Theory of Descent/' Eng. trans, by Prof. Meldola. 



