ON MIMICRY AND DECEPTION 



observation, their shells being photographically sensitive 

 for a short time after the caterpillars' skins have been 

 shed, so that each individual assumes the colour most 

 prevalent in its immediate vicinity ; this interesting fact 

 not being generally known, I last year reared caterpillars 

 of swallow-tail and white butterflies for the purpose of 

 obtaining chrysalides for exhibition at a meeting of the 

 Entomological Society. The mode of procedure was sug- 

 gested by me in Becreativc Science for July 1860, p. 

 35, and is simply as follows : — ' Caterpillars were obtained 

 and reared on their proper food-plants, and when full-fed 

 were placed in boxes, the insides of which had been 

 coated with colours of different kinds ; as soon as they had 

 fixed themselves, the boxes were opened and exposed to 

 sunlight in a window. The most successful specimens of 

 colouring in the chrysalides were obtained when the 

 changes took place on bright days, and when the in- 

 dividuals were surrounded by a quantity of the same 

 colour as that on which they were placed. Under these 

 conditions, the markings peculiar to the species were 

 greatly overpowered when necessary to the assimilation of 

 colour; they were, in fact, completely overpowered, and 

 replaced by bright green in chrysalides of the swallow-tail 

 (Papilio machaon) and white butterflies now in my pos- 

 session. I also exhibited a great number of chrysalides of 

 the two common species of white butterflies taken from 

 the stone-coloured sides of a house. Against one of the 

 sides a grape-vine was trained, and here the chrysalides 

 of both species were green, being affected by the light 

 shining through the leaves. On the bare side of the 

 house not a single green specimen could be found, and a 

 glance at them conveys an accurate idea of the colour of 

 the surface to which they have attached. As caterpillars 

 are evidently unaffected by colour in their choice of a 



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