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 Recreative 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 
341 
