XXXVI 



In this connection there is, therefore, question only of a greater or lesser 

 increase of black and this in relation to the susceptibility thereto, but this is 

 simply identical with the chief element of colour change, which I term colour 

 evolution, and which plays so important a role in imagines, which I first 

 observed in the larvae of Sphingidae and subsequently also in other larvae, and 

 to which, on page XXI of my introduction to the treatise of the Java Pieridae, 

 I attributed the increase of black in Pieris pupae. When we reflect that the 

 pupae which have been dealt with actually occur in two colour forms: green, 

 from yellowish to various darker shades, and grey, through various shades to 

 almost black, and that these two forms occur side by side in different indi- 

 viduals of the same species, such as : Papilio Machaon L., P. Polydamas L., 

 P. Demoleus L., and P. Memnon L., and thus produce a pupal dimorphism, 

 the matter will admit of no doubt to any one acquainted with the phenomenon 

 of colour evolution. Wherever such a dimorphism occurs it points to the 

 existence of an evolutionary process of change in which a certain number of the 

 members of such a species have advanced further than the others which possessed 

 little susceptibility in this respect sothat two distinct forms, each exhibiting a 

 different stage in this process, have been produced. Exactly the same process 

 obtains in the case of the green Sphingidae larvae turning brown, which is 

 dealt with in my article " Uebcr die Farbe iind den Polyinorpliismus der Sp/iiugiden 

 Raupen ", and in which the course of the process can be distinctly observed 

 owing to the separation of the various stages of development by the moults. 



In this case there is not only a very great difference — doubtless representing 

 many centuries of development — between the various species as regards the 

 stage of this evolution attained, but even between the individuals of the same 

 species there is a considerable disparity in this respect. The different shades 

 in which colours occur in pupae of the same species also point in that direction, 

 namely to a general darkening tendency which in different individuals, however, 

 is more or less developed. But to those well acquainted with the phenomena 

 of colour evolution this is by no means all. I distinctly remember, and Jacobson 

 also observes, that the dark brown-greyish pupae of Pap. Memnon L. exhibit 

 green dots ; Vosseler notes the same concerning the dark pupae of Pap. 

 Demoleus L. Whence these dots? They are relics or vestiges of the ancient 

 green colour of the pupae which in certain spots have resisted the evolutionary 

 darkening process; these are the same persistent spots to which I have already 

 referred when discussing the Pieridae, as regards the process of colour evolution. 



In so far as the colour of pupae is still subject to this process and suscepti- 

 bility is present, its course may be accelerated by the influence of favourable 

 conditions of life. Now it appears that at a certain period shortly before 



