The Saüba ant is peculiar to tropical America, and, though it is injurious to the wild native trees of the country, it seems to have a preference to the coffee and orange trees and other imported plants. The leaves which the Saüba cuts and carries away are used to "thatch the domes which cover the entrances to their subterranean dwellings, thereby protecting from the deluging rains the young broods in the nests beneath." The insects proceed according to a most orderly method, "the heavily-laden workers, each carrying its segment of leaf vertically, the lower edge secured in its mandibles, troop up, and cast their burdens on the hillock; another body of laborers place the leaves in position, covering them with a layer of earthy granules, which are brought one by one from the soil beneath." The labors of this curious insect are immense, and no obstacles stop their excavations. An allied species of Rio de Janeiro worked a tunnel under the bed of the river Parabyba, at a place where it is as broad as the Thames at London Bridge. These ants are sad rogues, being household plunderers and robbers of the farinha, or mandioca meal, of the poor inhabitants of Brazil; and Mr. Bates was obliged to lay trains of gunpowder along their line of march to blow them up, which in the end resulted in scaring the burglars away. We have already alluded to the massive heads possessed by the major and subterranean kinds of neuters, and stated that the work is done by the worker minor or small-headed kind. With regard to the function of the large-headed worker major, Mr. Bates was unable to satisfy himself: "They are not the soldiers or defenders of the working portion of the community, like the armed class in the termites, or white ants, for they never fight. The species has no sting, and does not display active resistance when interfered with. I once imagined they exercised a sort of superintendence over the others; but this function is entirely unnecessary in a community where all work with a precision and regularity resembling the subordinate parts of a piece of machinery. I came to the conclusion, at last, that they have no very precisely defined function. They cannot, however, be entirely useless to the community, for the sustenance of an idle class of such bulky individuals would be too heavy a charge for the species to sustain. I think they serve in some sort as passive instruments of protection to the real workers. Their enormously large, hard, and indestructible heads may be of use in protecting them against the attacks of insectivorous animals. They would be, on this view, a kind of _pièces de résistance_ serving as a foil against onslaughts made on the main body of workers." But the third order, the subterranean kind, we are told, is the most curious of all: