VAHIABLE PEOTECTIVE RESEMBLANCE IN INSECTS 139 



the food-plant, although I exammed the nettle-beds 

 where many hundreds of caterpillars had been feeding 

 and had left for pupation. All these three pupae were 

 dead, being filled with the parasitic larvse of Ichneumon 

 flies. In 1888 I found many more pupae upon the 

 food-plant, but a very high percentage of these had 

 been killed by parasites, and the hurrying on of 

 pupation which occurred in the other cases and pre- 

 vented the larvae from wandering in a normal manner 

 may, I think, be attributed to the state of health 

 induced by that extraordinarily wet season. 



The colours of certain dimorphic pupae cannot be adjusted 

 to the surroundings 



I have already mentioned that I experimented 

 upon the pupae of the Swallow-tailed Butterfly 

 (Pajnlio machaon), and found that they were not sus- 

 ceptible to the influence of surrounding colours. This 

 is also true of the small family of Mocha moths 

 (EphyjidcB) which have freely exposed pupae, fixed 

 like those of many butterflies by a silken girdle and 

 boss, and often appearing in two varieties, green and 

 brown. The caterpillars of the same species are also 

 of two colours, and always produce papas of corre- 

 sponding tints (see page 46). 



