( 09 ) VI. Notes on the Coloration and Development 0/ Insects, By P. Cameron. [Read 7tli April, 1880.] I. On the Markings on the Lary^ op Smerinthus. Last autumn I made an observation which may possibly throw some light on the use of the reddish-brown marks along the sides of the larvce of Smerinthus. My attention was attracted to a small poplar {Populus nigra) whose leaves were very much afiected with the small dark blotches caused by the fungus Melampsora i^opulina, Lev. "When examining these, I noticed that some of the blotches appeared to be of a brighter and redder tint. On pulling a leaf down which bore these differently-coloured markings, I found, somewhat to my astonishment, that they were not fungi, but the markings along the sides of a caterpillar of >S'. populi, which I had not observed before. The question then occurred to me : Might not the markings on the cater-pillar have been acquired in imitation of the fungi, so as to give it an additional means of protection, in conjunc-tion with the green colour of its body, in imitation of the green colour of the leaf ? To test this, the caterpillar was put back again on the tree, and the effect noticed. No doubt, looking at it close at hand, the larva was readily seen, for besides the slight difference in the colour of the lateral marks and the fungi (as already explained), the colour of the body was much brighter than the leaves, which were then (the end of September) beginning to fade ; but, looked at from a distance of several feet, the cater-pillar was certainly very difficult to see, and undoubtedly it seemed to me that the similarity of the spots to the fungi added not a little to hide it. Several other cater-pillars Avere found on neighbouring trees (likewise infested with fungi), and the examination of these served to confiim my first impression of the usefulness of the marks in hidiijg the larva in the circumstances in which it lived. The markings on the three species of Smerinthus are variable, and may be entirely absent. Mr. Boscher, for instance {Proc. Ent. Soc., p. xliv., 1878), describes two forms of trans, ent. soc. 1880. — part ii. (june.)
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