Species of the Genus Limenitis. 451 



are practically identical with those oi genutia. The distri- 

 bution of the latter also favours the same conclusion, for 

 it extends far beyond the tropics into Western and Central 

 China. 



Anosiais the outcome of a much earlier invasion, allow- 

 ing time for modification and the acquisition of characters 

 of generic rank in the new home. Danaida hercnice is the 

 result of a far more recent immigration. The Old World 

 parents of the two American forms were probably closely 

 allied or may even have belonged to the same species at 

 different periods of its history. There is strong evidence 

 in the mimicry of these two genera by species of Limenitis 

 {Basilar cilia) that the relative periods of residence in 

 North America were as they have been indicated above. 

 Details will be supplied in later pages. It will be suf- 

 ficient to point out here that the evolution of X, archippus, 

 Cr. (misippus, F.), from the characteristic type of Holarctic 

 Limenitis presented by its ancestor L. (B.) arthemis, Drury, 

 has involved an entire change to a new and highly elabor- 

 ate pattern on both surfaces, — a process which even the 

 most ardent mutationist can hardly conceive to have been 

 a rapid one, — especially when the mimetic pattern hits 

 off so precisely the characteristic details of the model. 

 Danaida hcrenicc has however merely modified into resem- 

 blance with itself — a likeness attained by a few simple but 

 perfectly effective changes — the mimic already fully 

 formed under the influence of Anosia. In fact, distinct 

 and evident details of the earlier mimicry of L. (B.) arch- 

 ippus still persist, and somewhat detract from the 

 mimetic resemblance attained by its descendant, fioriden- 

 sis, Streck. (cros, Edwards). 



The effects produced by both Danaine models upon the 

 butterfly fauna of North America, combined with the 

 absence of such effects in the tropical New World, support 

 the conclusion that residence in the north has been far 

 longer than in the south, and that the south was reached 

 by way of the north. It is probable that the Old World 

 ancestor of Anosia spread northward along the eastern 

 borders of Asia, and entered America by way of the 

 Aleutian Islands, and that its astonishing northern range 

 dates back to the period of the invasion. The ancestor of 

 Danaida ierenice may have followed the same route during 

 some temporary amelioration of climate, enabling this 

 more tropical form to reach its present home in the New 

 TRANS. ENT. SOC. LOND. 1908. — PART III. (DEC.) 30 



