Holland by
a still different but undescribed type.[928] The European bee (_Apis
mellifica_), although not a native of the new world, is now established
both in North and South America. It was introduced into the United
States by some of the early settlers, and has since overspread the vast
forests of the interior, building hives in the decayed trunks of trees.
"The Indians," says Irving, "consider them as the harbinger of the white
man, as the buffalo is of the red man, and say that in proportion as the
bee advances the Indian and the buffalo retire. It is said," continues
the same writer, "that the wild bee is seldom to be met with at any
great distance from the frontier, and that they have always been the
heralds of civilization, preceding it as it advanced from the Atlantic
borders. Some of the ancient settlers of the west even pretend to give
the very year when the honey-bee first crossed the Mississippi."[929]
The same species is now also naturalized in Van Diemen's Land and New
Zealand.

As almost all insects are winged, they can readily spread themselves
wherever their progress is not opposed by uncongenial climates, or by
seas, mountains, and other physical impediments; and these barriers they
can sometimes surmount by abandoning themselves to violent winds, which,
as I before stated, when speaking of the dispersion of seeds (p. 618.),
may in a few hours carry them to very considerable 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.[930]

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
Selbourne, spreading at the same time in great clouds all along the vale
from Farnham to Alton. These aphides are sometimes accompanied by vast
numbers of the common lady-bird (_Coccinella septempunctata_), which
feed upon them.[931]

It is remarkable, says Kirby, that many of the insects which are
occasionally observed to emigrate, as, for instance, the Libellulae,
Coccinellae, Carabi, Cicadae, &c. are not usually social insects; but seem
to congregate, like swallows, merely for the purpose of emigration.[932]
Here, therefore, we have an example of an instinct developing itself on
cert