450 Prof. E. B. Poulton on the Mimetic N. American 



The argument may be briefly recapitulated as follows : — 

 The fact tliat the distasteful foreign species, invading 

 temperate North America from a very different area, 

 should not only maintain their characteristic original 

 appearance under such different conditions, but should 

 compel the ancestral residents in their new home to 

 resemble them, is entirely inconsistent with an interpret- 

 ation of mimicry based upon the supposed influences of 

 locality (soil, food, climate, etc.). 



In attempting to make out the past history of the North 

 American Danaines, it is of paramount importance to 

 ascertain their affinity with the Old World species ; for it 

 is admitted that their relationship to all other New World 

 genera is remote. Rothschild and Jordan have recently 

 stated that Tasitia is inseparable from the genus Danaida 

 {Limnas) which contains the well-known chrysijjpus, L., 

 and its forms.* I therefore wrote to my friend Dr. Karl 

 Jordan, enquiring whether he had considered the affinity 

 of these forms to the New World Anosia and the Old 

 World Salatura. He kindly replied as follows : — " I think 

 that all the tawny Danaids [Limnas, Salatura, Tasitia, 

 Anosia] are one genus, with the exception of the large 

 [Anosia] plexip^ns. This insect differs as larva in having 

 only two pairs of filaments t and as imago in the cell of the 

 hind-wing being very long. The differences given by 

 Moore for Limnas, Tasitia and Salatura do not at all hold 

 good, neither the shape of the wings nor the position of 

 the veins being constant." 



Accepting this conclusion, the name Anosicc plexippus, L. 

 {archippus, F.), will be retained in the present memoir, 

 while hercnice, Or., and its form strigosa, Bates, will be 

 placed in the genus Danaida. It is impossible to speak 

 with certainty as to the Old World species which most 

 nearly represent the invading ancestors of the North 

 American Danaines. A safe conclusion can only be arrived 

 at after a searching investigation into the structural details 

 of many species. But there can be little doubt that 

 Danaida (Salatura) genutia, Or. {plexi2')pus, L.), presents 

 many of the features of this ancestor. Thus the white 

 markings upon the hind-wing under surface of D. bcrenice 



* '■'■Danaida chrysippi is cannot be generically separated from the 

 American ijilippus and hereniee, Limnas beint;- a synonym pure and 

 simple of Tasitia." Nov. Zool., vol. x, Dec. 1903, p. 502. 



t See, however, the note on p. 488. 



