112 Mr. G. A. K. Marshall 07i Diaposemntism, with reference 



colouring. In these circumstances the supposed difficulty 

 in regard to Arclionias evidently vanishes. It is no longer 

 remarkable that it has not developed the metallic effects 

 of the $ F((pilio ; indeed it would be much more remark- 

 able if it had actually done so. The mimicry has simply 

 followed the line of least resistance, and is in every way 

 consistent with the interpretation of a simple Miillerian 

 approach. It is possible that a fuller knowledge of the 

 habits of the insects would throw more light on the 

 matter ; for I note that Wallace mentions that in several 

 species of this group of Fapilto the sexes do not inhabit 

 the same stations (Trans. Ent. Soc. II, 1854, p. 255). 



Another point raised by Dr. Dixey, in support of his 

 interpretation that the Papilio has been influenced by the 

 Pierine, is Miiller's statement (Proc. Ent. Soc. 1879, p. 

 xxiv) that in the Santa Catharina district of Brazil Pap. 

 ncjyhalion, which there represents the model, was com- 

 paratively scarce while Arch, tereas was common. But in 

 the same paper (p. xxv) MitUer has expressly uttered a 

 warning against any such deduction from his statement : 

 ' Thus the black Arclionias tereas, with the white spots on 

 the margin of the fore-wings and the rose-red of the hind- 

 wings, presents a strange appearance among its congeners, 

 whilst Papilio nephalion belongs to a long series of similarly 

 coloured species, so that where this Pa2nlio is rare and 

 the Archonias common, we cannot for this reason regard 

 the latter as the model of the former." Unfortunately 

 Miiller does not mention whether he had observed any 

 other species of the numerous zaci/ntJms-Yike Papilios in 

 Santa Catharina, for this would be of great importance in 

 interpreting the facts. It remains however that all local 

 observers are agreed that the type of colouring exhibited 

 by zacynthus is the most characteristic, abundant and 

 dominant Papilio pattern in Brazil, and perhaps in Tropical 

 America ; nor do any species which I have seen show the 

 least sign of having been influenced by Archonias. It may 

 be noted that the mimetic forms of these Pierines per- 

 sistently retain a characteristic Archonias marking, namely, 

 a pale costal streak on the under-side of the hind-wing. 

 Now, if they had really exercised a strong influence on 

 the colouring of the Papilios as suggested, it seems only 

 reasonable to suppose that we should find some effect pro- 

 duced by this characteristic stripe. But no trace of it can 

 be seen either in P. nephalion or any other species of the 



