THE ENTOMOLOGIST. 55 
parts, one of which went eastward and the other westward, 
gradually falling upon the land. They were not long in 
ascertaining that what they had taken for a cloud was an 
immense concourse of small yellow butterflies (Terias Lisa, 
Boisd.), which flitted about all the open grassy patches and 
cultivated grounds in a lazy manner, as if fatigued after their 
long voyage over the deep. Fishermen out near the reefs, 
some few miles to the north of the islands, 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 vigorous appetites 
of the blue bird (Sialia sialis, Baird) and black bird (Minus 
carolinensis, Gray), which were continually preying upon 
them. Only one other instance ofa flight of these butterflies 
visiting the islands is recorded (in my ‘ Naturalist in Ber- 
muda,’ p. 120). 
Mr. Darwin, in his  Naturalist’s Voyage of H.M.S. Beagle,’ 
writes as follows :—Several times when the ship 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 Blas, 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 seaman cried out “it was snowing butter- 
flies,” and such in fact was the appearance. More species 
than one were present, but the main part belonged to a kind 
very similar 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 migrations of another butterfly, 
Pyrameis Cardui (Lyell’s ‘ Principles of Geology,’ vol. iii. 
p- 63), but the presence of other insects makes the case distinct, 
and even less intelligible. Before ,sunset a strong breeze 
