some British East African Butter files. 525 



species swarming together over an immense range, and both 

 probably equally distasteful. Evidence that Coloinis is the 

 model is yielded by a comparison of the northern and 

 southern forms of both species. The northern Eueidcs, 

 although diverging from the southern in the same manner 

 as the Colz&nis, has not changed to so great a degree. In 

 other words, the Colmnis leads and the Bueidcs follows. 



It is interesting to note that greater conspicuousness 

 due to size may act in the same manner as greater con- 

 spicuousness due to pattern. Amauris dominicanus as 

 contrasted with A. echeria, etc, seems to be an example of 

 dominance due in large part to pattern. (See p. 432.) 



These causes of predominant influence are of course 

 relatively rare, the usual causes being greater unpalatability 

 and superior numbers. Thus in nearly all the examples 

 of mimicry figured in the four plates accompanying this 

 memoir, the mimics are larger than their models, but the 

 latter belong to the highly protected Danainai and the 

 genus Mylothris. The mimicry of the larger red and black 

 Acrseas by the immense Papilio antimachus, Dru., is a 

 grand example of models far smaller than their mimic. 

 There can be no doubt however that the models are here 

 enormously more abundant and probably more distasteful 

 than their gigantic mimic. In the case of Planema- 

 Acriea and of CoLxnis-Eueidcs discussed above, there is not 

 the same evidence for discriminating widely between the 

 palatability and the relative abundance of the members of 

 each pair. Their difference in size remains as an 

 important distinction, and in both cases there is evidence 

 that the larger species has acted as the model. 



E. B. P. 



b. Bed-and-hlaclc Combination centred ly large Acr/eas. 



The commonest species in this group is ,Acrwa natalica, 

 Boisd., which is often very abundant, e. g. at Taveta. There 

 are however several other Acrseas which come into this 

 group, though the distribution of the black spots on the 

 red ground varies a good deal. These include A. acara^ 

 Hew., A. anemosa, Hew., A. areca, Mab., and A. pharsalus, 

 Ward. Together with these must be associated the larger 

 Nymphaline butterfly Pseudacrxa trimenii, Butl., which is 

 connected with the other species as regards pattern by 

 A. acara, as regards size by A, areca. 



