Species of the Genus Limenitis. 449 



kindly lending me the specimens represented in Figures 2 

 to 8 on Plate XXV, and the authorities of the British 

 Museum of Natural History for the originals of Figures 1 

 and 10. 



THE DANAINE INVASION OF THE NEW WORLD 

 AND THE CONSEQUENT MODIFICATION OF 

 NORTH AMERICAN SPECIES OF LIMENITIS. 



One of the most interesting problems of mimicry and 

 migration in butterflies is raised by the consideration of 

 these North American Danaines. The genera to which 

 they belong extend throughout the tropical New World, 

 but, although represented by excessively abundant indi- 

 viduals, they enter into no synaposematic relations with 

 any of the Neotropical combinations. They mimic nothing 

 and nothing mimics them in tropical America. On the 

 other hand, in North America they supply models for 

 some of the very best examples of mimicry in the North 

 temperate zone. Considering these facts, it is clear that a 

 suggestion published by the present writer in 1901 is 

 erroneous. Anosia plexippiis {archippus, F.) cannot have 

 had its ancestral home in South America or have invaded 

 the northern belt from the immediate south. The argu- 

 ment founded on a supposed southern source is, however, 

 unaffected and has so direct a bearing on a common 

 hypothesis as to the origin of mimetic resemblances that I 

 venture to quote it on the present occasion: — "In the 

 New World the genus Limenitis is confined to the Nearctic 

 Region with the exception of a single species, a form of the 

 mimetic L. astyanax (Fabr.), which just enters the borders 

 of Mexico. If butterfly colours and patterns are the 

 expression of the direct influences of the environment, 

 then it is clear that the indigenous non-mimetic species of 

 Limenitis {Basilarchia) are an expression of Nearctic con- 

 ditions, and according to the theory of External Causes, 

 the invader from the South should have come to resemble 

 them instead of drawing an ancient Nearctic species far 

 away from the ancestral colours and patterns into a close 

 superficial likeness to itself"* This argument is, as I 

 have said, unaffected, because the Danaine is clearly an 

 invader, although not from South America. 



* " Verhandl. d. V. Internat. Zool. Congr. z. Berlin." Jena, 1902, 

 p. 171. 



