MR PIEPERS ON COLOUR IN LEPIDOPTERA. 233 



when we take into consideration the phenomenon of genepistasy, 

 so called by the late German naturalist Prof. Dr Eimer, which 

 causes the continuation of a certain colour in one of the stadia for 

 an indefinite time. 



If the fact is already long known that the caterpillars of the 

 above-named family, belonging to the same species, appeared in 

 different colours, and that in this respect the different ontogenetical 

 stadia are at variance, no one, as far as I am aware, has stated the 

 universality of this fact nor the constant succession of these colours 

 in a certain order, so as to infer from this the general phenomenon 

 of a regular succession of changes. On this account I think I may 

 consider myself the discoverer of this phenomenon (which I also 

 observed in caterpillars of other families) and give it a name. And 

 the name I have selected is " evohctioji of coloui'." For though it 

 consists in the revelation of a hitherto unobserved phenomenon as 

 far as the colour of insects is concerned, it is indeed nothing else than 

 the well-known fact called evolution, that all animal forms are con- 

 stantly subject to organic changes in one direction or another — 

 though they may now and then come to a temporary standstill. 

 Thus the name of ^' cvohitioii of colour'' seems to me to be the 

 proper term. 



Before I had come to this conclusion I had perceived that the 

 remarkable cases of polymorphism among the imagines of the 

 Lepidoptera, of which I had been able to study at my leisure the 

 most characteristic example, that of Papilio inei)inon, L., during 

 my 30 years' stay in the Malayan archipelago, did not simply con- 

 sist, as so many think, in the fact that by the side of the cT several 

 different forms of the % exist, which forms also vary among them- 

 selves as well as from the </, but that all these varieties compared 

 together manifest only the result of changing colours passing over 

 from one to the other, making a series of which the ^ forms one 

 extreme and the female variety differing most from the </, Papilio 

 achates Cram., the other. Indeed at the last International Con- 

 gress of Zoology, which took place at Leyden, I stated this fact, as 

 can be read in the reports of that Congress. But no sooner was the 

 phenomenon of ''evolution of colour" clear to me than I found in it 

 the solution of this polymorphism. 



In just the same manner as the shades of colour pass over one 

 into the other in the above-mentioned caterpillars they also pass 

 over one into the other in the different forms of imagines of Papilio 

 mcmnon L., therefore it seemed clear to me that this polymorphism 

 too could be nothing less than such an " evolution of colour'' which, 

 however, not only shows itself as a difference in colour between the 

 species, but in these imagines also between the sexes of a same 

 species. Now we are taught by investigations on the group of 

 Papilionidae to which Papilio memnon L. belongs — in connection 

 with other groups of the same family — and in particular by com- 

 parison of that butterfly with its next allied form found in the 



