290 Professor E. B. Poulton on Mimetic Forms of 



(2) Trophonius. This form possesses the pattern of 

 Mppocoon, but white has been replaced by fulvous over the 

 great continuous patch occupying most of the hind- and a 

 large part of the fore-wing. The remaining pale markings 

 are white, so that the yellow of triincni in part originated 

 white and in part fulvous,- — a more complex change than 

 that which produced liippocoon. Considering the identity 

 of pattern I first supposed that troplionius arose from 

 hippocoon instead of having an independent origin in the 

 trimeni. Although the former view may be correct, the 

 latter is I think more probable, being strongly supported 

 by an interesting specimen from the Kikuyu Escarpment, 

 in the Hope Department. In this butterfly the great 

 patcli is fulvous except upon the distal border of the part 

 upon the fore-wing. Tiiis border, together with all the 

 other pale markings on both wings, is not white like 

 hipp)Ocoon, but retains the yellow of trimeni. The specimen 

 furthermore possesses a rudimentary " tail " nearly as 

 much developed as that of the trimeni represented on 

 Plate XVIII, Fig. 1, while the sub-marginal yellow spots 

 of the hind-wing are very large and prominent, far more 

 so than in the particular specimen of tTimcni ]ws>i referred 

 to. This specimen, with its primitive features, strongly 

 supports the direct independent origin of troplionius from 

 trimeni, the most convincing evidence being supplied by 

 the pale markings which had not been converted into 

 white, but remained of the ancestral yellow. 



The troplionius form at any rate of the merope sub- 

 species appears to be more unstable and is pi'obably a more 

 recent development than either of the other mimetic 

 female forms hiiypocoon and planemoides. A specimen in 

 the Plope Department (Angola : Rogers : 1873) presents a 

 very primitive form of the oblique black bar dividing the 

 two chief pale spaces of the fore-wing. It is even less 

 developed than in a specimen of clioiiysos in the same col- 

 lection and much like that of the tihulhos trimeni represented 

 on Plate XIX, Fig. 1. Merope troplionius is very apt to 

 appear as a variety in which the fulvous tint overspreads 

 the whole of the pale markings of both wings. One of 

 the two polytrophus troplionius forms at Oxford is of this 

 variety. It is moreover a very poor mimic of Limnas 

 chrt/sippus as compared with the smaller more deeply- 

 coloured troplionius of the eeneci sub-species (Plate XVII, 

 Fig. 7). It is also noteworthy that the merope tropjlionius 



