296 IMPERFECT SOCIETIES OF INSECTS. 



1839, when cloud-like swarms of these insects (chiefly L. depressa) were 

 seen at Weimar, Eisenach, Leipsig, Halle, and Gottingen, and the inter- 

 vening country, extending over a very large district. 1 Professor Walch 

 states, that one night about eleven o'clock, sitting in his study, his attention 

 was attracted by what seemed the pelting of hail against his window, which 

 surprising him by its long continuance, he opened the window, and found 

 the noise was occasioned by a flight of the froth frog-hopper (Aphrophora 

 spumaria), which entered the room in such numbers as to cover the table. 

 From this circumstance, and the continuance of the pelting, which lasted 

 at least half an hour, an idea maybe formed of the vast host of this insect 

 passing over. It passed from east to west ; and as his window faced the 

 south, they only glanced against it obliquely. 2 He afterwards witnessed, 

 in August, a similar emigration of myriads of a kind of ground beetle 

 (Amara vulgaris).* But the most remarkable migrations of beetles are 

 those recorded by M. Lacordaire, who informs us that for two successive 

 years, when he was at Buenos Ayres, that city was for about eight days in 

 the spring of each year inundated by such millions of Harpalus cupripennis, 

 which arrived daily towards nightfall, that it was necessary every morning 

 to sweep them from the exterior of the houses to a height of several feet 

 above the ground. 4 Another writer in the Naturforscher, H. Kapp, ob- 

 served on a calm sunny day a prodigious flight of the noxious cabbage 

 butterfly (Pontia Brassic<\ which passed from north-east to south-west, 

 and lasted two hours. 5 Kalm saw these last insects midway in the British 

 Channel. 6 A similar migratory column of the universally spread Vanessa 

 Cardui, of from ten to fifteen feet in breadth, and the passage of which 

 occupied two hours, was observed in 1836 in the canton of Vaud, Switzer- 

 land. 7 Lindley, a writer in the Royal Military Chronicle, tells us, that in 

 Brazil, in the beginning of March, 1803, for many days successively there 

 was an immense flight of white and yellow butterflies, probably of the same 

 tribe as the cabbage butterfly. They were observed never to settle, but 

 proceeded in a direction from north-west to south-east. No buildings 

 seemed to stop them from steadily pursuing their course, which being to 

 the ocean, at only a small distance, they must consequently perish. It is 

 remarked that at this time no other kind of butterfly is to be seen, though 

 the country usually abounds in such a variety. 8 In the instance of the 

 butterflies mostly of a species similar to, if not identical with, the common 

 English Colias Edusa, seen by Mr. Darwin and Captain Fitzroy when at 

 sea, about ten miles from the bay of St. Bias, on the coast of South 

 America, and which were in such countless myriads (occupying, according 

 to Captain Fitzroy's calculation, a space of not less than a mile in width, 

 several miles in length, and two hundred yards in height) that the sailors 

 exclaimed, " It is snowing butterflies : " their object in flying out so far to 

 sea would seem to have been a voluntary migration, as Mr. Darwin states 

 that the day had been fine and calm.. 9 Major Moor, while stationed at 



1 Weissenborn in Mag. Nat. Hist. X. S. iii. 516. 



2 Naturforsch. vi. 111. 3 Ibid. xi. 95. 



4 Lacordaire, Introd. a FEntom. ii. 494. 



5 Naturforsch. 94. 6 Travels, i. 13. 



7 Silbermann, Revue Entorn. ii. 142. 



8 R. Milit. Chron. for March 1815, p. 452. 



9 Narrative of the surveying Voyages of his Majesty's Ships Adventure and 

 Beagle, iii. 185. 



