THE ENTOMOLOGIST. 55 



parts, one of which went eastward and the otlier 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 fesv 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 of a 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 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 liee from 

 butterflies. The seaman cried out "it was snowing butter- 

 flies," and such in fact was tlie appearance. More species 

 than one were jiresent, but the main part belonged to a kind 

 very similar to, but not identical wilh^ the common English 

 Colias Edusa. Some moths and Hymenoptera accompanied 

 the butterflies, and a fine beetle (Calosoma) flew on board. 

 'J'he 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 ofT the land, but we 

 must conclude that they voltmtarily took flight. The great 

 bands of the Colias seem at fust to aflbrd 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 



