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Ch. XL.] 



MIGEATION OE INSECTS. 



379 



settlers of tlie west even pretend to give tlie very year wlien 

 tlie lioney-bee first crossed the Mississippi.^ Tlie same species 

 is now also naturalised in Van Diemen's Land and New 



Zealand. 



As almost all insects are winged, tliey can readily spread 

 themselves wherever their progress is not opposed by un- 

 congenial climates, or by seas, mountains, and other physical 

 impediments ; and these barriers they can sometimes sur- 

 mount by abandoning themselves to violent winds, which, as 

 I shall afterwards state when speaking of the dispersion of 

 seeds (p. 386), may in a few hours carry them to very consider- 

 able distances. On the Andes some sphinxes and flies have 

 been observed by Humboldt, at the height of 19,180 feet above 

 the sea, and which appeared to him to have been involuntarily 

 carried into these regions by ascending currents of air.f 



Inundations of rivers, observes Kirby, if they happen at 

 any season except in the depth of winter, always carry down a 

 number of insects, floating on the surface of bits of stick, 

 weeds, &t3. ; so that when the waters subside, the entomolo- 

 gist may generally reap a plentiful harvest. In the dissemi- 

 nation, moreover, of these minute beings, as in that of plants, 

 the larger animals play their part. Insects are, in number- 

 less instances, borne along in the coats of animals, or the 

 feathers of birds ; and the eggs of some species are capable, 

 like seeds, of resisting the digestive powers of the stomach, 

 and after they are swallowed with herbage, may be ejected 

 again unharmed in the dung. 



White mentions a remarkable shower of aphides which 

 seem to have emigrated, with an east wind, from the great 

 hop plantations of Kent and Sussex, and blackened the 



shrubs and vegetables where they alighted at Selborne, 



spreadin 



vale from rarnham to Alton. These aphides are sometimes 

 accompanied by vast numbers of the common lady-bird 

 [Coccinella septempundata) ^ which feed upon them.f 



It is remarkable, says Kirby, that many of the insects 

 which are occasionally observed to emigrate, as, for instance, 



^ Washington Irving's Tour In the gions— Malte-Erun, vol. v. p. 379. 

 Prairies, ch. ix. j Kirby and Spence, vol. ii. p. 9. 



t Description of the Equatorial Ee- 1817. 



at the same time in great clonds all along the 



