164 MIMICRY IN N. AMERICAN BUTTERFLIES 



through a crowded area without producing any 

 effect on any member of the Lepidopterous 

 fauna, or without themselves being affected 

 thereby. ' ! Abundant wide-ranging Danaines 

 in the Old World, even when much smaller 

 and with a less marked appearance, invariably 

 produce some effect, and often themselves 

 exhibit Miillerian resemblances. 



THE EVOLUTION OF LIMENITIS (BASILARCHIA) 

 ARCHIPPUS AS A MIMIC OF THE INVADING 

 DANAIDA PLEXIPPUS 



It has already been mentioned that a single 

 species, undergoing corresponding modifications, 

 provides a mimic for each of the three Danaine 

 models (including strigosa). We will first con- 

 sider the well-known beautiful mimic of D. plex- 

 ippus; for it undoubtedly arose earlier than the 

 others. 



The abundant Limenitis or Basilarcliia archippus 

 is closely related to the Palaearctic species of 

 Limenitis, a group which includes the well-known 

 British 'White Admiral' (L. sylilla). The ex- 

 ample is unusually instructive, because the non- 

 mimetic ancestor of the mimic is still very 

 abundant in Canada and the north-eastern States, 

 and we thus possess the material for reconstruct- 

 ing the history by which the one form originated 

 from the other. We know that this ancestor, 

 Limenitis arthemis, has persisted almost unchanged, 



1 Trans. Ent. Soc. Lond. (1908), 452. 



