26 



that until further evidence is forthcoming one is tempted to 

 regard them as hybrids between a wandering male from further 

 south, carrying tendencies of the mimetic females, and the 

 ordinary female of antinorii. Omitting these from consideration 

 until further specimens have been obtained, the antinorii male 

 and female are closely similar to the Madagascar meriones, except 

 for a considerable reduction of black on both the wings of both 

 sexes. The female still presents the black mark on the costa 

 which is the beginning of the mimetic pattern. 



I next place upon the frame the most interesting of all the 

 subspecies, namely polytrophus, from the lofty eastern edge of 

 the great Rift Valley, near Nairobi in British East Africa (Plate II, 

 Figs. 3 to 9). Here, on the Kikuyu Escarpment, at an elevation 

 of 6,500 to 9,000 ft., we meet with all the mimetic forms of the 

 female dardanus, together with innumerable intermediates and 

 an abundant ancestral form, trimeni, which has not entirely 

 lost the yellow ground-colour of the male and non-mimetic 

 female, and shows a prolongation of the costal mark towards 

 the posterior angle of the forewing, giving in difterent individuals 

 every transition between a marking well-nigh as rudimentary 

 as that of the meriones female itself, and the fully formed bar 

 of hippocoon (cf. Figs. 2, 6, 7, and 8 on Plate II). It is charac- 

 teristic of the ancestral trimeni females that they are exceedingly 

 variable, and especially so in the degree of development of the 

 bar crossing the forewing. They further commonly exhibit a 

 vestigial trace of the " tail " to the hindwing (Figs. 6 and 9). 

 Comparison between Figs. 6, 7, and 8 shows that the fully 

 formed mimetic female hippocoon, resembling in East Africa the 

 Danaine model Amaiiris niavius dominicanus (Plate I, Fig. 2), 

 has been derived from trimeni by the transformation of the 

 yellowish ground-colour into white, and the sharpening of the 

 outlines of the most fully developed black pattern. Comparison 

 with Fig. 9 shows that the trophonius form, mimetic of Danaida 

 chrysippus (Plate I, Fig. 3) over the whole Ethiopian region, is 

 derived directly from trimeni by a fulvous flush overspreading 

 the principal pale area extending over a large part of both 

 wings. In the interesting example represented in Fig. 9 the 

 flush does not cover the whole of this area, and the uncovered 

 part, as well as all the other pale markings, are of the yellowish 



