35 



Mimicry in the Nortli American Butterflies of the Genus 



Limenitis. 



By Prof. E. B. Poulton, F.R.S., F.L.S. Bead October 23rd, 1913. 



{The paper of irltich an. abstract is f/ireii heloiv icas illustrated h>j 

 numerous lantern slides.) 



The models Danaida ple.vippiis [arcJiipptis), D. herenice and />. 

 strif/osa belong to the old world Danaines, and are to be regarded as 

 modern invaders of the American Continent. D. plexippiis probably 

 came in by way of the north, and it even now ranges far into 

 Canada. It is to be looked upon as the American equivalent of the 

 old world I), r/eniitia (plexippiis) which may probably have extended 

 north along the eastern Asiatic coast, and crossed at Behring 

 Strait during some temporary amelioration of climate. That it 

 invaded America by way of the north is well shown by the fact that 

 it has produced an excellent mimic in temperate North America 

 only. It ranges with slightly varying pattern through tropical 

 America to the temperate south, but nowhere has it produced an 

 undoubted mimic except in the north.^ The other two Danaine 

 forms, D. berenice and D. stri/josa, are the New World representatives 

 of D. chrysippns. These are less suited to a cold climate, and are 

 only found in the southern States. They also may have invaded 

 America by way of the north — although considerable amelioration 

 would here be required — or it is possible that they were accidental 

 immigrants across the Pacific. They are probably not distinct 

 species, but geographical races the one of the other, and, like 

 plexippiis, extend southward through tropical America with slight 

 changes of pattern. They also resemble plexippiis in the fact that 

 they have undoubted mimics in North America only. 



The Nymphaline Liiiienitis, or as its North American forms are 

 called Basilarchia, is a characteristic circumpolar group, of which 

 the majority of forms in both the Old World and the New, possess 

 the well-known pattern made up of broad white markings upon a 

 black background. A good example is our English sibi/lla, and the 

 European Camilla, and a very similar pattern is found in the North 

 American artltemis and iveidermeyeri, as also in lorquini, although 

 here the pale part of the pattern is cream coloured. 



1 It is possible thp.,t there is an incipient mimic among the South Americiin 

 Acriciiuv of the genus Actinote. 



