Notes on some British East A^frican Butter Jlics. 551 



^Ground "colour much darker ; white markings of upper 

 side conspicuously reproduced ; interncrvular black rays 

 better developed. Hind-winfj : basi-costal border fulvous. 



Type of male from 16 miles west of Shimba, near 

 Mombasa, about 1200 ft. Type of female from Rabai, 

 July 28, 1906. The above description was made from 

 these two specimens in the collection of the Hope Depart- 

 ment of the Oxford University Museum. 



The difterences from the West African Psettdacraict 

 cvrytas, L., presented by this interesting new congener 

 consist mainly in the reversal in the fore-wing of the 

 relative development of the sub-apical bar and the inner- 

 marginal patch, and in the very much greater develop- 

 ment of the centi'al patch in the hind-wing. There can, 

 I think, be no doubt that these features indicate very 

 clearly the mimetic approximation of the just-described 

 East African ally of eu7i/tus to the common Acrseine, 

 Plancrna montana, Butler,* of the same region. Ps. eurytus, 

 as is well known, mimics to perfection the abundant 

 Planema cjJcea, Cram, (gea, Fab.), of Western Africa, 

 reproducing in each sex the narrow sub-apical bar and 

 high truncated inner-marginal patch of the fore-wings, and 

 the narrow sub-basal patch of the hind-wings, with much 

 exactness both in form and colour. Ps. rogersi $ has not 

 attained the same close imitation as far as the fore-wing 

 markings are concerned, the retention of an inner- 

 marginal patch diminishing the likeness to PI. montana 

 which has undoubtedly been gained by the quite peculiar 

 position, curvature, prolongation, and inner indentation 

 of the sub-apical bar ; but it is very noticeable that — as 

 in many other cases of mimicry — the $ rogersi has pro- 

 ceeded further on the mimetic path, the inner-marginal 

 patch in the fore- wings having reached almost as reduced 

 and evanescent a stage as in the ^ Pscudacrma imitatar. 

 Trim., in her simulation of Planema aganice. 



The members of the eurytus-gxovi^ of Pscudacraia stand 

 out most prominently among mimetic butterflies in the 



* Aurivillius (Rhop. ^thiop., 1899, p. 121) has treated this form 

 as a Variety of the South African Planema aganice, Hewits. ; but, 

 considering how very closely allied most of the recognised species of 

 Planema are, it seems better to hold it entitled to species rank, 

 because of the much broader bands in both wings — especially in the 

 (^ , where they are moreover of a warm fulvous instead of yellowish 

 or yellowish-white ; in this sex also the basal area on the upper side 

 of the hind-wing is strongly red-tinged. 



