730 THE BUTTERFLIP:S of new ENGLAND. 



by about a dozen other species of smaller butterflies." Finally, I was 

 myself fortunate enough to observe a movement of this sort during the au- 

 tumn of 1888 between nine and ten o'clock in the morning of September 

 2 ; while sitting on the piazza of a house facing the sea-shore at Hampton, 

 N. H., and only a stone's throw from the water, a continuous stream of 

 these butterflies passed before me toward the southwest, following the 

 line of the sea-coast, with the wind about northwest. There were never 

 less than three or four directly in front of me, often a dozen or twenty. 

 In the hour that I watched them, I calculated that at least fifteen hundred 

 passed me and without a single exception in the same direction. 



Mr. Roland Thaxter, who found great swarms of this butterfly festoon- 

 ing the trees in a pine grove in northern Florida (as detailed further 

 on), says he "was told by Dr. A. W. Chapman" — the most competent 

 authority living — "that there was hardly milk weed enough in all Florida 

 to produce one of these flocks." Moreover, Dr. Chapman states that in 

 Apalachicola the butterflies are very abundant annually from November 

 until May ; after that but few are seen until fresh ones appear in the mid- 

 dle of October. Flocks, too, ha,ve since been observed in Florida, wan- 

 derers no doubt from the north, like our invalids, seeking a climate best 

 permitting hibernation. And in these facts we find an explanation of these 

 migrations. All or nearly all are descendants of those which at the end 

 of the previous season flew to warmer climes and dispersed in the spring 

 in search of milk Aveed. The same was true of their ancestors of a corre- 

 sponding time of year, the rugged season having eliminated the greater 

 number of those which, when the autumnal season warned, stayed behind, 

 so that they left no descendants. In this way an instinct, an inherited 

 tendency, grew up, which is probably annual and nearly if not quite 

 universal, but to wliich our attention is drawn only in those years in which 

 the species is superabundant. 



Commercial extension in recent years. Among the most interest- 

 ing points in the distribution of this butterfly is the fact that within thirty 

 years or a little more, it has begun to invade so many regions of the world 

 as to make one think at first blush that it may some day vie with Vanessa 

 cardui in cosmopolitan character. The facts concerning its exotic distri- 

 bution, so far as I have been able to gather them are as follows : It first 

 reached the Hawaiian Islands, fully two thousand miles distant from Amer- 

 ica, sometime not far from 1845 to 1850. At any rate we have the direct 

 statement of Dr. Luther H. Gulick who was born upon the islands, that 

 in 1852, after eleven years' absence, he returned to the islands, and his 

 brother drew his attention to the fact that Asclepias had been introduced 

 during his absence and had already become a troublesome weed ; that his 

 brother had noticed that wherever the milk weed appeared, there also 

 Anosia made its advent, a butterfly unknown until after the milk weed 



