104 Mr. W. L, Distant's Geograjjhical Distribution, ^c. 



Supposing one of these swarms to be blown out to sea by 

 a strong gale, again carried on by the prevalent winds, 

 many ever succumbing, a few still being borne along, this 

 remnant gradually becoming less, often totally extinct, 

 but at some favoured time a floating trunk becoming a 

 shelter for hybernation, the ocean currents bearing many 

 of these trunks along their streams, few, very few being 

 cast at all on an opposite continent or island, and still 

 fewer that should possess a hybernating butterfly, and we 

 shall at once see how seldom colonization by these means 

 would be, and yet how efficacious a movement of disper- 

 sion it becomes. We have also seen how its food plant 

 has by the agency of man been carried to most of the 

 countries where it has found a new home, and that its 

 ova may have been carried by the same agency. But 

 though its dispersal by these means is necessarily of a very 

 slow and rare description, its survival in a new abode has 

 been seen to have everything in its favour. The wide 

 range of its food plant is combined with an immunity from 

 attacks of enemies, whilst its rapid mode of effecting its 

 transformations renders it capable of completing its cycle 

 of existence during a short summer and hybernating 

 through a cold winter in temperate climes, or through a 

 time of drought in the torrid zone. Nature seems thus to 

 reveal one of her processes, which appearing to depend on 

 something allied to chance, yet in her own good time 

 effects those complexities of faima which not the Ento- 

 mologist alone finds in examining typical faunas one of 

 the most involved problems and unexplained phenomena. 



Since reading the above, I have been referred to a paper 

 by Dr. Semper, " Die Wanderung von Danais Erippus, 

 nach den Siidsee-Inseln, Australien und Celebes," pub- 

 lished in the "Journal des Museum Godeffroy," Heft IV., 

 which I have as yet been unable to see. 



