The Origin of the Markings of Caterpillars. 305 



natural selection. If, as I believe, it can and has 

 been shown, not only that caterpillars in general 

 possess adaptive colours, but that these colours 

 can change during the lifetime of one and the 

 same species, in correspondence with external 

 conditions, we must certainly gain a very high 

 conception of the power which natural selection 

 exerts on this group of living forms. 12 



12 [In the class of cases treated of in the foregoing portions 

 of this essay, the external conditions remain unaltered during 

 the lifetime of the caterpillar, but change of habit, and in some 

 cases of colour, occurs when the insect has attained a size 

 sufficient to make it conspicuous. Cases are, however con- 

 ceivable a priori, and are realized by observation, in which the 

 environment itself may undergo change during the lifetime of 

 the individual caterpillar. Thus, in the case of hibernating 

 species, the colour which is adaptive to the autumnal colours 

 of the foliage of their food-trees would not assimilate to that 

 of the newly-opened leaves in the spring. I have already 

 quoted (Proc. Zoo. Soc. 1873, p. 155) as instances of what may 

 be called " seasonal adaptation," the larvae of Geometra Papilio- 

 naria, Addalia Degeneraria, and Gnophos Obscurata, and many 

 more could be named. These species undergo a change of 

 colour before or after hibernation, the change being always 

 adaptive to the environment. 



It has long been known that caterpillars which feed on 

 flowers or on plants of variously-coloured foliage, in some cases 

 partake of the colour of their food. See, for instance, Dr. L. 

 Holler's memoir, " Die Abhangigkeit der Inseckten von ihrer 

 Umgebung," 1867, and B. D.Walsh " On Phytophagic Varieties 

 and Phytophagic Species," Proc. Ent. Soc. Philadelph., vol. 

 iii., p. 403. In 1869 Mr. R. McLachlan published a paper 

 entitled " Observations on some remarkable varieties of Sterrha 

 Sacraria, Linn., with general notes, on variation in Lepi- 

 doptera" (Trans. Ent. Soc. 1865, p. 453), in which he gave 

 many illustrations of this phenomenon. The larva of Hdiotlm 



X 



