in Butterflies of the Genus Precis. 37 



sesamus at Pretoria might be adduced as corroborative 

 evidence, and similarly the typical octavia would appear to 

 be scarcer on the West Coast than its dry form ; further, the 

 typical dry form of P. archesia has been occasionally observed 

 at the height of the wet season, and in the case of P. artaxia, 

 Hew., the experiences of both Mr. F. C. Selous and myself 

 appear to show that in the low-lying coast districts of 

 Portuguese Manika the leaf-like typical form alone occurs all 

 the year round, whereas on the plateaux of the interior the 

 summer form is represented by P. Nachtigalii, Dew., the 

 typical form occurring only in the winter, and being generally 

 more plentiful. That this view of the subject is a necessarily 

 correct one I would not venture to assert, but in the light of 

 the foregoing facts it is at least probable. 



On the other hand it is not impossible that the nalalensis 

 form may present an instance of mimetic coloration in its 

 incipient stage ; at all events it possesses some very marked 

 potentialities for development in that direction should the 

 stress of circumstances ever call them into play. The scheme 

 of colouring, as a whole, very notably recalls that of an Acrcea 

 in certain respects, this being especially the case on the 

 underside of the hind wings, where the basal black patch 

 enclosing some subquadrate whitish spots, the pink discal 

 field traversed by a transverse row of black spots, and, finally, 

 the black hind marginal border with its row of lunules are 

 all characters which find a close parallel in the widespread 

 Acrcea acara, Hew., and its various local representatives. 

 The upperside also presents several features suggestive of 

 Acrcea, and it is worth noting that the red ground-colour is 

 clearly due to a great enlargement of the common submar- 

 ginal band so characteristic of the genus Precis ; moreover, 

 the ialcation of the primaries and the anal angular projection 

 of the secondaries is less developed in this species than in 

 any other of the genus. I do not suppose the foregoing 

 suggestion will find much favour with those entomologists, 

 unfortunately not a few, who are still inclined to throw doubt 

 on the grand theory of Batesian mimicry — a theory the truth 

 of which is continually being brought home to the observant 

 collector in the tropics, and with ever-increasing force. 



In considering the problem of seasonal dimorphism it at 

 once becomes evident that the directly exciting cause is a 

 climatic one. The splendid series of experiments made by 

 European observers, such as Prof. Weismann, Dr. Standf uss, 

 and Mr. Merrineld, appear to leave no doubt that in that 

 region the dimorphic tendency is brought into action by heat 

 and cold, and that humidity plays practically no part therein. 



