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VII. On Biaposeinatism, with reference to some limitations 

 of the Mi'dlerian Hypothesis of Mimicry. By GuY 

 A. K. Marshall, F.Z.S. 



[Read February 5th, 1908.] 



One of the most striking features in connection with the 

 philosophical study of the phenomena of Mimicry among 

 butterflies in recent years has been the marked tendency 

 to lay an ever increasing emphasis upon the importance 

 of the selective factors suggested by Fritz Mliller and to 

 minimise the influence of what is known as Batesian 

 Mimicry. It has even been suggested that every known 

 case of mimicry among butterflies can be more satis- 

 factorily interpreted as being due to the operation of 

 Mliller's principle. The essential difference between 

 these two theories of mimicry lies in the fact that one 

 explains how an edible (or less unpalatable) species will 

 derive advantage through assuming a superficial likeness 

 to another which possesses nauseous (or more unpalatable) 

 qualities (Batesian mimicry); whereas the other shows 

 how one nauseous species will benefit by mimicking 

 another having the same qualities (Miillerian mimicry). 

 Now although there can be little doubt that a good many 

 cases of mimicry originally adduced in support of Bates' 

 theory must now be explained on Miillerian lines; yet 

 the universal application of this latter principle to butter- 

 flies, involving, as it does, the assumption of unpalatability 

 in every mimic, seems open to some serious objections 

 which may be considered later. 



Perhaps the principal stimulus to the recent extension 

 of Midler's interpretation of mimetic resemblances has 

 been furnished by an hypothesis which has been developed 

 by Dr. F. A. Dixey. It was in his important and able 

 memoir on the Phylogeny of the Pierinse (Trans. Ent. Soc, 

 1894, pp. 249-334) that Dr. Dixey first outlined his 

 conception of Diaposematism, or Reciprocal Mimicry, as it 

 was then called. This conception consists practically of 

 a widening or complication of the principle put forward 

 by Mliller to explain the inter-resemblances between 

 distasteful butterflies belonging to different genera. For 



TRANS. ENT. SOC. LOND. 1908. — PART I. (MAY) 



