vr SENSITIVENESS— MIMICRY 337 



and appearing of another colour. In some cases the result of 

 the change was to hring the colour of the larva into harmony 

 with its surroundings, but in others it was not so. During the 

 final stage many larvae are susceptible, the result being made 

 evident only when the pupa is disclosed. Variably coloured 

 pupae of certain species of butterflies have long been known, and 

 it has been shown that some of the varieties can be induced by 

 changing the surroundings. The result of the changes is in 

 certain cases correspondence between the colour of the individual 

 and its surroundings. In the case of other species having pupae 

 of variable colour, the colour of the pupa is without relation to, 

 or harmony with, the surroundings. 



Experiments have been made on pupae by Merrifield and 

 others, with the result of showing that by changes of tempera- 

 ture applied at certain moments some of the colours or marks of 

 the butterfly that will emerge can be altered. 



It is found that in certain localities the colour of various 

 kinds of butterflies more or less agrees, while it differs from 

 that of the same butterflies found in other localities. Thus 

 Weir speaks of a duskiness connnon to various butterflies in 

 Java, and calls it "phaeism" ; and Bates states that in the Amazon 

 valley numerous species of butterflies vary in a similar manner, 

 as regards colour, in a locality. This phenomenon is now called 

 " homoeochromatism," and is supposed to be due to the effect of 

 local conditions on a susceptible organisation, though there is no 

 experimental evidence of this. 



Mimicry. — There are many cases in Lepidoptera of species 

 that depart more or less strongly in appearance from those forms 

 to which they are considered to be allied, and at the same time 

 resemble more or less closely species to which they are less allied. 

 This phenomenon is called mimicry.^ Usually the resembling 

 forms are actually associated during life. Bates, who observed 

 this phenomenon in the Amazon valley, thought that it might 

 be accounted for by the advantage resvilting to the exceptionally 

 coloured forms from the resemblance ; "^ it being assumed that 

 these were unprotected, while the forms they resembled were 



^ Tlie term mimicry is sometimes used in a wider sense ; but we think it better 

 to limit it to its original meaning. The word is a most unfortunate one, being 

 both inadequate and inaccurate. 



^ Trails. Linn. Soc. xxiii. 1862, p. 507. 

 VOL. VI Z 



