XV THE RELATION OF FACTS TO THEORIES 319 



mimicry, displaying itself only in the females, and 

 not in all of these. According to M. Piepers, it is 

 to be explained on the ground that the polymorphic 

 forms represent successive stages in the transition 

 between one monomorphic species and another. He 

 is of opinion that the Papilionidae of the Malay are, 

 for the most part, descended from ancestors with 

 large spatulate appendices to the hind wings, but 

 that many have lost or are losing these. In the two 

 series P. Memnon-Androgeos and P. Theseus-Pammon, 

 the species are undergoing this transition ; the males 

 and some of the female forms display the new type 

 of structure, while certain of the female forms display 

 in part ancestral traits. The resemblance between 

 these female forms respectively and the other two 

 series of butterflies (P. Coon-Doubledayi and P. Hector- 

 Diphibis-Antiphus) is not so great in the field as in 

 the study, and is merely due to the fact that these 

 two series display a more primitive type of structure 

 and coloration, one nearer to that displayed by the 

 hypothetical ancestor of the Eastern Papilionids. 



The whole question is considerably complicated 

 by the great variability of all the Papiliones, which 

 makes it practically impossible to distinguish be- 

 tween species and varieties ; while, on the other hand, 

 the nomenclature employed has a considerable bear- 

 ing on the question of mimicry, at least when repre- 

 sented in tabular form. The mimicking females of 

 P. Memnon and P- Androgeos are exceedingly alike, 

 so much so that they were formerly classed together 

 as one species. The chief difference is that the 

 Javan form has yellow spots, while the Indian form 

 has reddish. In the species P. Coon and P. Double- 



