122 



men out near the reefs, some few miles to the north of the is- 

 lands, very early that morning, stated that numbers of these 

 insects fell upon their boats, literally covering them. They did 

 not stay long upon the islands, however, only a few days, but 

 during that time thousands must have fallen victims to the vig- 

 orous appetites of the blue bird QSialia sialis Baird) and black 

 bird (Mimus carolinensis Gray), which were continually prey- 

 ing upon them. Only one other instance of a flight of these 

 butterflies visiting the islands is recorded (in the author's 

 "Naturalist in Bermuda" p. 120). 



The migratory habit of the Pieridae, to which the present 

 species belongs, is well known, and notices of the occurrence of 

 large flights have occasionally appeared in entomological jour- 

 nals. Numbers of 'Pier is napi and P.brassicae have been known 

 to cross the channel from France to England, and a migratory 

 host of Callidryas radio, has been observed moving along in 

 Basuto Land ; but the only instances published of their having 

 been met with at sea, are to be found in Darwin's " Naturalist's 

 Voyage " and the " Entomologist's Magazine" (England). 



Darwin writes as follows: — Several times when the ship 

 (H. M. S. " Beagle ") has been some miles off the mouth of 

 the Rio Plata, and at other times when off from the shores of 

 northern Patagonia, we have been surrounded by insects. One 

 evening, when we were about ten miles from the Bay of San 

 Bias, vast numbers of butterflies, in bands or flocks of countless 

 myriads, extended as far as the eye could range. Even by the 

 aid of a telescope it was not possible to see a space free from 

 butterflies. The seamen cried out " it was snowing butterflies," 

 and such in fact was the appearance. More species than one 

 were present, but the main part belonged to a kind very simi- 

 lar to, but not identical with, the common English Colias edusa. 

 Some moths and Hymenoptera accompanied the butterflies, 

 and a fine beetle (Calosoma) flew on board. The day had 

 been fine and calm, and the one previous to it equally so, with 

 light and variable airs. Hence we cannot suppose that the 

 insects were blown off the land, but we must conclude that 

 they voluntarily took flight. The great bands of the Colias 

 seem at first to afford an instance like those on record of the 



