A Deceptive Caterpillar. 281 



recent book on "The 'Colours of Animals," and the same 

 investigator has more recently published' extensive researches 

 on the subject, a summary of which may be found in an 

 article^ by the present writer. The particular caterpillar 

 whose portraits are given on PL 7, does not, however, seem 

 to have been specially noticed in this connection. The 

 opportunity of photographing a living specimen was, there- 

 fore, worth seizing, both on that account, and also for the 

 purpose of directing attention to a fascinating branch of field 

 natural history in which the camera will prove a valuable 

 weapon to the naturalist. For the photographs on PI. 7, our 

 best thanks are due to Mr. F. T. Eason. 



Not only in form, but in colour and markings, does this 

 caterpillar correspond with its surroundings. The greenish- 

 grey lichen, covering the surface of the rose- twigs, is beauti- 

 fully imitated by the mottled pattern on the insect's back, 

 light greenish patches on a dark background irresistibly 

 suggesting the patches of lichen on the wood. This cater- 

 pillar, like many other loopers, is variable, being sometimes 

 dark, and sometimes light or greenish. In Prof. Poulton's 

 memoir, already mentioned, it is shown that the colour of a 

 looping caterpillar often depends upon its surroundings in its 

 early stages. Young caterpillars of Boarmia repajidata and 

 other geometrid moths reared among dark twigs grew up 

 dark, while those reared among green shoots were light or 

 greenish in hue. The dark colour is due to pigment in the 

 skin ; when this pigment is scanty, or absent, the green of the 

 underlying tissue shows through. By a series of beautiful 

 experiments. Prof. Poulton proves that the presence of certain 

 yellow rays of the solar spectrum hinder the formation of the 

 dark pigment. These rays are absorbed by dark objects, but 

 are reflected from green leaves and shoots ; and hence comes 

 the wonderful power of the caterpillar to correspond in colour 

 with its environment. This power is, however, lost after the 

 third or fourth moult, for no change could be induced in the 

 insects by altering their surroundings at that stage. It must 

 be remembered that caterpillars do not, as a rule, change 

 their habitat naturally; they are hatched, grow up, and 

 pupate on the same plant. Hence it is enough that they 

 be sensitive in their young stages. There can be no doubt 



1 Trans. Ent. Soc. Lond. 1892. ^ 2^atural Science, April, 1893. 



