in existence, probably from Africa, and even some Danaidae belonging entirely 

 to one of the Malayo-Australian forms. To the latter, for instance, belongs the 

 great traveller Danais (Anosia) Plexippus L. 



In the course of ages land connections have presumably existed repeatedly 

 between South America and Africa and it is very remarkable, therefore, how 

 the presence in America of butterflies of the Danaid type belonging to different' 

 groups indicates different periods of migration which becomes explicable only 

 through the repeated existence of such land connections at different periods. 

 The oldest of these connections existed presumably at that period when the 

 continents of America, Africa and Indo-Australia, now terminating southwards 

 in apices, were connected with the antarctic continent and with each other 

 consequently, during a tropical climate, a fairly remote period, but during 

 which the original Danaidae may well have been in existence. The two later 

 connections may well be presumed to have existed between West Africa and South 

 America. That the Danaidae have spread from the old world to America, and 

 not vice versa, appears from the circumstance that not only the Neotropidae but 

 likewise the others in America have acquired mostly the peculiar elongated 

 American form of wings, so characteristic of the Heliconidae, but which the 

 Danaidae of the old world do not possess, a phenomenon occurring also in 

 butterflies of other orders, as for instance the Pieridae, Acraeidae, and Nym- 

 phalidae, and in such a manner that this process in these has not advanced 

 to the same extent and some Pieridae are very clearly in a period of transition 

 in this respect. This reveals, indeed, a process of change, gradually continuous 

 and, consequently, where this has already been completed, initiated long ago 

 which, therefore, must point Hkewise to the existence of an ancient land connection, 

 although of a more recent date than that from which the Neotropidae resulted. 

 But some species of Danaidae occurring also in America, as has already been 

 stated, have all retained the form of wing of the old world, as for instance 

 Dan.\is (Anosia) Plexippus L. a fact which appears to indicate that they 

 must have been subjected for a relatively short period to the influences, to be 

 discussed more fully presently, which cause the form of wing in America to 

 change. This can only be understood on the assumption of another later 

 migration and, therefore, of a still later land connection in more recent times. 

 For the existence of these land connections moreover, there is much probability 

 on geological grounds. 



A great tendency, or rather, adaptability for migrating evidently exists in 

 this family. One species, Danais (Anosia) Plexippus L., already referred to, 

 which, like Vanessa Cardui L. in Europe, migrates in large swarms, so-called, 

 has, like the latter, spread over a large portion of the world. In a similar 



