452 Prof. E. B. Poiilton on the Mimetic N. American 



World. At the northern boundary of the Neotropical 

 Region — now running east and west from Mexico City to 

 points on the |AtIantic and Pacific coasts considerably 

 further north — the southward migration of both Danaines 

 was probably checked for a considerable period. Held 

 back for a time at the limits of that crowded area, teeming 

 with the species of the allied Ithomiin^, they finally in 

 comparatively recent times forced their way southward and 

 spread through South America, even reaching, in the case 

 of Aoiosia, the south temperate zone. All this has been 

 so recent that only insignificant changes — probably sub- 

 specific — have occurred, and no mimetic or synaposematic 

 relationship has been formed.* 



The hypothesis set forth above has the one merit that it 

 accounts for the facts, puzzling as many of them are. The 

 phenomena in the northern zone are unique, and as for those 

 of the tropics, there is no other case where Danain,v of such 

 marked size and appearance range through a crowded area 

 without producing any effect on any member of the Lepi- 

 dopterous fauna, or without themselves being affected 

 thereby. If a striking comparison be desired, no better 

 instance can be selected than the three African species of 

 the genus Mdinda (Tirumala), the products of an invasion 

 from the Oriental Region. Of these three species T. 

 formosa, Godm., and T. mcrcedonia, Karsch, are mimicked 

 respectively by Papilio rex, Oberth., and its form mimeti- 

 cus, Rothsch., while T. morgeni, Honrath, is itself mimetic 

 of the characteristic Ethiopian Danaine genus Amauris. 



It is, perhaps, unnecessary to state that in speaking of 

 this Danaine invasion of tropical America, I leave out of 

 account the remarkable Danains& forming the section 

 Lycormini. These are at once shown by their structural 

 peculiarities no less than by their intimate association 

 with the great synaposematic groups to be very ancient 

 inhabitants of the Neotropical Region. 



The evolution of Limenitis (Basilarohia) archip- 

 pus. Or. (misippus, F.), and its forms as mimics of 



THE INVADING DaNAINES. 



L. arcMppus is rightly considered by S. H. Scudder as 

 the most striking example of mimicry in temperate North 



* It is however possible that a large Peruvian form of Actinote 

 thalia, L. (or anteas, Dbl., Hew., if these two fornis can be kept dis- 

 tinct), is an incipient mimic of Anosia. 



