Pcqnlio dardanus (mcrojjc) and Acrma johnstoni. 291 



does not, so far as I am aware, present a variety with 

 white hind-wings like the forms of Limnas ehrysiiyims, var. 

 alci'ppus, universal on the west coast. 



Troiohonius forms, although probably always relatively 

 rare, occur in all five sub-species distinguished by Dr. 

 Jordan. 



(3) Ccnea. Here too it is almost certain that the 

 female form developed direct from trimeni, the ancestral 

 yellow ground colour being transformed into buff without 

 first becoming white. The evidence is similar to that 

 advanced in the case of the last female form, but is 

 stronger, inasmuch as there is not in ccnea that close 

 resemblance to the pattern of Jdppocoon which is borne by 

 tro'phoniiLs. Comparing the trimeni on Plate XVIII, 

 Fig. 1, with the hippocoon in Fig. 2, and the cenca in 

 Fig. 3, — all poJytroplius, forms from the Escarpment, — it is 

 at once seen that the change from the apical half of the 

 fore-wing of the ancestral form to that of ccnea is nearly 

 as simple as the change to liippocoon. For the rest of the 

 pattern, ccnea requires only a more widespread invasion 

 of black than liippocoon. There are six examples of 

 polytrophus ^ f. ccnea in the Hope Department, and all 

 exhibit primitive characteristics in the pale tint of the 

 chief patch of the hind-wing. In none is this buff like the 

 Danaine models, but it is pale yellowish like trimeni in 

 three, and pale yellowish with a faintly brownish tinge in the 

 other three, including the specimen represented on Plate 

 XVIII, Fig. 8. In five cases the chief spot of the fore- wing 

 follows the tint of the hind-wing patch, in the sixth the 

 chief spot is white. The other spots on fore- and hind- 

 wings are generally pale yellowish, sometimes white. It 

 is quite clear that we have in three specimens a stage in 

 the transformation of the ancestral yellow tint into buff. 

 It is of interest to observe that the pattern of the ccnea, 

 form is completely attained in three specimens whose pale 

 colour remains entirely ancestral. Not one of the six 

 specimens exhibits rudimentary "tails," althougli the sub- 

 marginal hind-wing spots are strongly developed. (Plate 

 XVill, Fig. 3.) 



The ccnea % form is dominant in the sub-species ccnea 

 of the south and south-east, and common in polytrophns of 

 the Kikuyu Escarpment. It occurs, but more rarely than 

 liippocoon, in other parts of British East Africa, as a 

 female form of tihullus and of the intermediate f'oruis round 



