274 THE ENTOMOLOGIST. 



in Britain at an earlier period than the species which {ceteris 

 2)aribus) do not exist in these islands. But with butterflies 

 such evidence is scarcely satisfactory. Furnished with wings, 

 and of light gravity, they may have been introductions of a much 

 later date. On the other hand, they may have once existed, but 

 been killed out by altered climatic conditions, and from their 

 perishable structure left no traces of their presence. 



If, however, we arrange the species in the order in which their 

 existence in the outl3dng islands would suggest, we arrive at the 

 following results : — 



Iceland was cut off before any of our species reached it, for 

 though six butterflies have been very doubtfully recorded from 

 that island, none of them are British species. 



From the Feeroe Islands I have seen no record of the occur- 

 rence of any butterflies. 



From Shetland only three species have been recorded, viz., 

 Atalanta, Cardui, and Typhon. 



In Orkney the following have been noticed: — Atalanta, Cardui, 

 Typhon, Brassica, RapcB, and Icarus. ■ 



In the Hebrides, Brassica, Typhon, and Icarus. 



In Ireland thirty-nine or forty species, of which a list was 

 given at the beginning of this paper, and which include in their 

 number all the few species of the other islands. 



If any dependence can be placed on evidence such as this, one 

 might conclude that Typhon was one of the earliest to come to 

 Britain, and seeing that it is an arctic species, and considering 

 the nature of the places which it inhabits, and the food-plant of 

 its larva, I think some justification may be found for this 

 belief. 



Next in order to it I should be inclined to place Icarus, which 

 is also an arctic species. 



As for the others just mentioned, not much can be learnt from 

 their occurrence. Cardui and Atalanta are both strong flyers and 

 wanderers ; Brassicce and probably Rapce are both probably recent 

 introductions with cultivated cruciferous plants. 



We now come to the forty Irish species. As has been 

 already mentioned, many naturalists hold, and on good grounds, 

 that the main part of the fauna and flora of Ireland reached that 

 island by way of Scotland, and that, in fact, the species were 

 Scottish before they became Irish. But, however true this may 



