222 [March, 



700 miles from the nearest land (the African coast), still strong on the 

 wing and apparently in good order. Mr. J. M. Jones records the 

 arrival of a vast swarm of the small and feeble Terias Lisa at Bermuda, 

 which had evidently crossed more than 650 miles of stormy ocean, from 

 the American coast ; and a swarm of Deiopeiapulchella (another weak 

 flyer) has been recorded in mid- Atlantic (Ent. Mo. Mag., vol. xxii, p. 12), 

 960 miles from the Cape de Yerde Islands^ the nearest land from which 

 the moths could have come, and where I have found the species in 

 plenty. 



It is, therefore, not difficult to imagine one of the great migrating 

 swarms of Anosia Flexippus being blown out to sea from the Cali- 

 fornian or Mexican coast, and travelling with the N.E. trade wind ; 

 the greater number by far perishing en route, but a few stragglers of 

 the host reaching the Sandwich Islands. This may have occurred many 

 times before the introduction of a suitable food-plant, in which case < 

 the butterfly necessarily failed to establish itself ; but once given the 

 AscJepias it would soon be quite at home. Thence it would have no 

 such tremendous expanses of ocean to traverse in order to reach new 

 lands ; the scattered islands (Fanning, Maiden, Starbuck, Christmas 

 Islands, and others), between the Sandwich group and those in the 

 South Pacific, although small and mostly barren, might serve as stepping- 

 stones in its progress. The distances between these islands, though 

 great enough, are nothing like the first great step from America to the 

 Sandwich Islands, and not more, I should imagine, than the light and 

 downy seeds of the Asclepias could be carried by the agency of winds, 

 &c., alone. 



As bearing on this origin of the Pacific specimens of Anosia 

 JPlexippus, it is significant that they all agree with the North American 

 type : the larger pale spots in the black apical portion of the fore-wing 

 being tawny, not white as in those from the Peruvian coast of South 

 America. 



The same remarks may apply to its dispersal across the Atlantic ; 

 but owing to the much more stormy character of this ocean, and the 

 less steady winds, the chances of the buttertiy crossing a given extent 

 of ocean in safety are less favourable. Still many American birds, 

 some scarcely, if at all, as strong on the wing as Anosia Flexipipus, find 

 their way to our shores from time to time, "We must also take into 

 account the chances of the insect resting by the way on some of the 

 numerous vessels constantly crossing the Atlantic, which, as Mr. 

 "Wallace suggests (Geog. Dist. of Animals, vol. i, p. 17), may materi- 

 ally aid the smaller and weaker birds in their occasional passage across 



