Papilio dardanus (merope) and Acrea johnston. 291 
does not, so far as I am aware, present a variety with 
white hind- wings like the forms of Limnas chrysippus, var. 
alcippus, universal on the west coast. 
Trophonius forms, although probably always relatively 
rare, occur in all five sub-species distinguished by Dr. 
Jordan, 
(3) Cenea. 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 cenea that close 
resemblance to the pattern of hippocoon which is borne by 
trophonius. Comparing the triment on Plate XVIII, 
Fig. 1, with the Aippocoon in Fig. 2, and the cenea in 
Fig. 3,—all polytrophus 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 cenea is nearly 
as simple as the change to hippocoon. For the rest of the 
pattern, cenea requires only a more widespread invasion 
of black than hippocoon, There are six examples of 
polytrophus 2 f. cenea 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 ¢éviment in 
three, and pale yellowish with a faintly brownish tinge in the 
other three, including the specimen represented on Plate 
XVIII, Fig. 3. 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 
1s 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 cenea 
form is completely attained in three specimens whose pale 
colour remains entirely ancestral. Not one of the six 
specimens exhibits rudimentary “ tails,” although the sub- 
marginal hind-wing spots are strongly developed. (Plate 
XVIII, Fig. 3.) 
The cenea 2 form is dominant in the sub-species cenea 
of the south and south-east, and common in polytrophus of 
the Kikuyu Kscarpment. It occurs, but more rarely than 
hippocoon, in other parts of British Kast Africa, as a 
female form of ¢ibu/lus and of the intermediate forms round 
