Man has undesignedly introduced into new districts perhaps fewer species of birds than of quadrupeds; but the distribution of birds is very much influenced by the character of his industry, and the transplantation of every object of agricultural production is, at a longer or shorter interval, followed by that of the birds which feed upon its seeds, or more frequently upon the insects it harbors. The vulture, the crow, and other winged scavengers, follow the march of armies as regularly as the wolf. Birds accompany ships on long voyages, for the sake of the offal which is thrown overboard, and, in such cases, it might often happen that they would breed and become naturalized in countries where they had been unknown before.[83] There is a familiar story of an English bird which built its nest in an unused block in the rigging of a ship, and made one or two short voyages with the vessel while hatching its eggs. Had the young become fledged while lying in a foreign harbor, they would of course have claimed the rights of citizenship in the country where they first took to the wing.[84] Some enthusiastic entomologist will, perhaps, by and by discover that insects and worms are as essential as the larger organisms to the proper working of the great terraqueous machine, and we shall have as eloquent pleas in defence of the mosquito, and perhaps even of the tzetze fly, as Toussenel and Michelet have framed in behalf of the bird.[85] The silkworm and the bee need no apologist; a gallnut produced by the puncture of an insect on a Syrian oak is a necessary ingredient in the ink I am writing with, and from my windows I recognize the grain of the kermes and the cochineal in the gay habiliments of the holiday groups beneath them. But agriculture, too, is indebted to the insect and the worm. The ancients, according to Pliny, were accustomed to hang branches of the wild fig upon the domestic tree, in order that the insects which frequented the former might hasten the ripening of the cultivated fig by their punctures--or, as others suppose, might fructify it by transporting to it the pollen of the wild fruit--and this process, called caprification, is not yet entirely obsolete. The earthworms long ago made good their title to the respect and gratitude of the farmer as well as of the angler. The utility of the earthworms has been pointed out in many scientific as well as in many agricultural treatises. The following extract, cut from a newspaper, will answer my present purpose: