IMPERFECT SOCIETIES OF INSECTS. 33 1 



entered the room in such numbers as to cover the table. From this 

 circumstance, and the continuance of the pehing, which, lasted at least 

 half an hour, an idea may be formed of the vast host of this insect pass- 

 ing over. It passed from east to west ; and as his window faced the south, 

 they only glanced against it obliquely.^ 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.-' Another writer in the JSatwforscher, H. Kapp, 

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

 butterfly {Pontia Brassicce), which passed from north-east to south-west, 

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

 Channel.^ 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, Swit- 

 zerland.^ 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.^ 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 Fitz- 

 roy 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 migra- 

 tion, as Mr. Darwin states that the day had been fine and calm.^ Major 

 Moor, while stationed at Bombay, as he was playing at chess one even- 

 ing with a friend in Old Woman's Island, near that place, witnessed an 

 immense flight of bugs (Geocorisce), which were going westward. They 

 were so numerous as to cover every thing in the apartment in which 

 he was sitting. When staying at Aldeburgh, on the eastern coast, I have, 

 at certain times, seen innumerable insects upon the beach close to the 

 waves, and apparently washed up by them. Though wetted, they were 

 quite alive. It is remarkable, that of the emigrating insects here enume- 



' Naturforsch vi. 111. * Ibid. xi. 95. 



3 Lacordaire, Introd. h I'Entom. ii. 494. 



* Naturforsch. 94. * Travels, i. 13. 



* Silbermann, Eevue Entom. ii. 142. 



' R Mint. Chron. for March 1815, p. 452. 



* Narrative of the surveying Voyages of his Majesty's ships Adventure and Beagle, iii. 185. 



