MIMETIC ASSOCIATIONS 



lOI 



DORIPPOIDES, Trimen, Plate X, Fig. ii. 



This peculiar form already described is at present but little known, and may be 

 found to occur in other subspecies. It mimics D. chrysippus dorippus. 



PAPILIO DARDANUS POLYTROPHUS, R. and J. 



This subspecies is found on the Kikuyu Escarpment. The individuals are distinguished 

 by their generally smaller size. It has the following female forms : — 



HIPPOCOON. TRIMENI, Plate X, Fig. 3. 



CENEA, Plate X, Fig. 15. planemoides 



TROPHONIUS. 



The trimeni form, as has already been described, is the least modified of all the female 

 varieties. Professor Poulton is of the opinion that it is from this form that all the other female 

 varieties have been derived.^ Certainly all the other forms can be easily traced through a 

 series of slight modifications from this variety. 



In Papilio dardanus the phenomenon of butterfly mimicry, not only in its existence, 

 but in its development, is beautifully illustrated. In Grand Comoro we have a primitive form 

 remaining in which the female only differs from the male in the slightly greater development 

 of the costal black bar. In Madagascar this marking has become larger and extended 

 towards the median nervure. The same feature appears in the Abyssinian form antinorii, 

 which has also produced two other varieties which throw a curious light on the possibilities 

 of mimetic development. We then have the trimeni form of female, and in a series of 

 examples of the subspecies polytrophus the gradual change can be seen through trimeni 

 to cenea on the one hand and to hippocoon on the other. It is of no consequence whether 

 trimeni be a survival of an early stage or a reversion, it remains an intermediate form and 

 shows what small changes may produce a beneficial resemblance to some suitable model. 

 Hippocoon may develop reddish-brown basal areas together with other smaller modifications 

 and the butterfly resembles chrysippus, or the dark areas may extend in imitation of Amauris, 

 or give place to a pale brown suffusion producing dorippoides. A modified hippocoon develops 

 yellow only on the fore-wings, and the planemoides form is produced. The male, with his 

 more powerful flight, is hidden when at rest by a perfect adaptation of cryptic coloration. 

 The early stages are protected by the same means, so that the larvae are most difficult to 

 find, and the pupae almost indistinguishable from leaves. The whole life-history of dardanus 

 is an illustration of the keen struggle for existence which is met by a development of mimetic 

 modification unparalleled in any other species with which we are acquainted. The most 

 earnest opponent of mimetic theory cannot deny the resemblance of the pupa to a leaf, 

 or that of the male, when at rest, to its surroundings. Why are Amauris echeria, alhimaculata, 

 and niavius, Danaida chrysippus, and Planema poggei unusually common butterflies, if not 

 by reason of some advantage which they enjoy in their relation to vertebrate enemies, and 

 how is it that out of the unlimited number of patterns which an unstable form like 

 dardanus might produce, the principal varieties happen to be those which most resemble 

 these plentiful and slow-flying species ? These are problems for which the opponents of 

 mimicry will have to find some much better explanation than those of climatic influence, 

 sexual selection, and parallel variation, before we can see any good reason to abandon 

 Bates's comparatively simple and wholly reasonable explanation. 



1 Trans. Ent. Soc, 1906, p. 288. Regarded in strict order of evolution this subspecies might preferably have 

 been inserted on p. 99, after P. dardanus antinorii. 



