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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.) 



