( 45 ) 



mimetic of the Aculeates. The methods of mimetic resem- 

 blance were varied — sometimes the likeness was in pattern an 

 not in movement, sometimes in movement and not in pattern, 

 but in the most perfect examples there was likeness in both. 



Returning to the history of the Colour-groups in the islands, 

 we probably found, in the effects of occasional and accidental 

 inter-island migration, an answer to Dr. Perkins's further 

 difficulty based on the number of the Colour-groups, especially 

 on Oahu. Whatever may happen in the vast complexity of a 

 tropical continental area, we should certainly have expected, as 

 Dr. Perkins maintains, the persistence or formation of single 

 Miillerian Colour-groups on each of these small islands, 

 although we ought to be prepared for possible exceptions in 

 groups of specially associated species, such as the six forming 

 Colour-group III (= C) on Oahu, all of which were captured 

 at one time and in one spot by Dr. Perkins. Such special 

 associations may have all the effect of geographical isolation in 

 encouraging the growth of special warning patterns. Leaving 

 such possible exceptions on one side, we should expect a single 

 Colour-group on a single island, but we should not expect the 

 same group to be formed independently in different islands, 

 lxii] 



and the mixture of groups was probably to be explained by 

 accidental transport froni one island to another. 



This was, in fact, Dr. Perkins's interpretation of the 

 existence of two Colour-groups on the most isolated of all the 

 islands, Kauai ; for he remarks that " excepting two species 

 (. . . probably recent derivations from similar forms on other 

 islands) the Kauai wasps have become superficially all alike." 

 Such complications are of course far more likely to occur in 

 the central islands of the chain — nearer together and liable to 

 receive immigrants from both directions. 



The following was an attempt to reconstruct the history of 

 the Colour-groups within the islands. It, in the main, followed 

 Dr. Perkins's account, but included a few suggestions bearing 

 on the mixture of the groups. 



(1) The original yellow-banded pattern persisted at any rate 

 in Oahu (the island nearest to Kauai), and probably through- 

 out the islands, until after the Structure-groups had been 



