IN DEFENSIVE COLORATION 337 



defined association. Some species like Papilio dardanus 

 (merope) have forms entering two or more of the com- 

 binations (see below and pp. 373-5). The condition 

 reached is probably stable: all the central patterns are 

 clear, well defined, and very distinct from one another, and 

 there is no reason for anticipating any tendency towards 

 further unification. When, however, we pass westwards 

 along the equatorial belt, it has already been pointed out 

 (see p. 335) that A, echeria and its ally, the central models 

 of perhaps the most important eastern combination, come 

 within the sphere of western species of Amauris and show 

 evident traces of influence. Why should the echeria-albi- 

 maculata type be influenced here and not along the East 

 Coast ? The answer is clear ; because the pattern of the 

 western Amauris is much nearer to that of the intruders 

 than any of the eastern species of the same Danaine genus. 

 This consideration suggests the probably sound conclusion 

 that it would be impossible for these particular models 

 from the East and West to form and keep distinct im- 

 portant combinations on the same area. 



When we turn to the West Coast the same phenomena 

 are met with. The Danaine models, when possessed of 

 the same general pattern, tend to approach one another, 

 or if the patterns be bold and isolated, to stand singly — in 

 either case forming the centres of Miillerian combinations. 

 In an extremely interesting example from the Cameroons, 

 an abundant and dominant type of Amauris has drawn 

 to it a species of a very different Danaine genus, Tirumala 

 (or Melinda), — T. morgeni. The resemblance is extra- 

 ordinarily close and deceptive. 



Having given examples of the changes that occur in 

 the central members of Miillerian groups, it is now 

 necessary briefly to describe the changes that occur in 

 a few of the outlying members. This can be well 

 illustrated from the eastern combinations which have 

 been mentioned above. One of the female forms of 

 Papilio dardanus [merope), the cenea form, is a beautiful 

 mimic of the ecfteria-a/6imacu/ata-centred combination. 

 As we pass westward, another bold and conspicuous 

 model, belonging to the Acraeinae, makes its appearance, 



