igog] Mimicry in the Butterflies of North America 209 



mimetic relations with any of the other butterflies of this southern 

 Region.^ Furthermore, they not only belong to a dominant Old 

 World section of the Danaines, but are even closely allied to par- 

 ticular species within it. It is probable that there are only two 

 well-marked species of Danaini on the American Continent, and 

 that the various forms encountered over this vast area are the 

 geographical races or sub-species of these two. In north tem- 

 perate America they are the well-known models for mimicry, — 

 Anosia plexipptis extending far into Canada, and Tcisitia herenice 

 and its form strigosa not ranging beyond the southern States. 



In 1897, at the Detroit meeting of the American Association for 

 the Advancement of Science, I suggested* that the Mimicry of 

 Anosia plexippus by Limenitis {Basilar chia) archippus was 

 evidence that the model had long resided in North America, and 

 that w^e might on this ground alone, even if we had not abundant 

 positive evidence of its gradually increasing spread in the Old 

 World during the past half-century, infer that Anosia had reached 

 Fiji, Australia, Hong-Kong, &c., in comparatively recent times. 

 This conclusion can hardly be doubted, and the argument might 

 have been extended to enable us to infer the ancestral line of 

 migration by which North America itself had been reached by 

 this form. But in 1897 I followed what appeared to be the gen- 

 eral view, that, in the New World, the original stream of Danaine 

 in\-asion had run from the American tropics north ward% nor did 

 I observe that the evidence based on the growth of mimetic 

 resemblance warranted the interesting conclusion that its flow 

 had taken the opposite direction, and that the south had been 

 peopled by way of the north. Accepting this conclusion, the 

 question arises: Whence came the Danaini of North America? 

 The answer requires a somew^hat careful comparison between the 

 New and Old World butterflies of this group. 



Among the commonest of the Old World Danaini, are certain 

 species with tawny colouring, a black border, and black white- 

 barred apex to the fore wing. The under surface is even more 

 conspicuous than the upper, being brighter in colour and the 

 black border marked with white in a more striking manner. In 

 one set of Oriental species, placed by Moore in his genus Salatura, 



^ It is possible, however, that there are incipient resemblances to Anosia in 

 certain S. American Acraeinae. 



*Proc. Am. Assoc. Adv. Set., 1897, xlvi. 244. 



■^ Verhandl. d. V. Internal. Zool. Congr. z. Berlin, 1901, Jena, 191)2, 171. See 

 also Essays on Evolution, (1908), 274; also errata. 



