Page:Popular Science Monthly Volume 7.djvu/273

Rh incision on the upper side; it then takes the edge between its jaws, and, by a sharp jerk, detaches the piece which is about the size of a dime. Sometimes they let the leaf drop to the ground, where a little heap accumulates, until carried off by another relay of workers; but generally each marches off with the piece it has operated upon, and, as all take the same road to their colony, the path they follow soon becomes smooth and bare, looking like the impression of a cartwheel through the herbage. The heavily-laden workers troop up and cast their burdens on the hillock; another relay of laborers place the leaves in position, covering them with a layer of earthy granules, which are brought up one by one from the soil beneath. It has not been shown satisfactorily to what use the leaves are put. It was formerly supposed that they were consumed as food. Mr. Bates's investigations convinced him that the leaves were used to thatch the domes which cover the entrances to the subterranean dwellings, thereby protecting from the deluging rains the young broods in the nests beneath. Mr. Belt, however, who observed the leaf-cutting ants in Central America, and gives a full and interesting account of them in his "Naturalist in Nicaragua," arrives at the conclusion that the leaves which they gather in such enormous quantities are used to form beds for the growth of a minute fungus, on which they and their young live. Fritz Müller, writing from Brazil (Nature, vol. x., p. 102), says that he has always held this view, and that an examination of their stomachs under the microscope confirms it.

This ant is so abundant in some districts that agriculture is almost impossible, and wherever it exists it is a terrible pest. It is also troublesome to the inhabitants from its habit of plundering the stores of provisions in houses at night, for it is even more active by night than in the daytime.

The principal part of the visible work is done by the small-heads (1, Fig. 1), while those which have massive heads, the worker-majors (2), are generally observed to be simply walking about. They are not, in this species, soldiers, for they never fight. The function of superintendence would seem superfluous in a community where all work with precision. 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. Prof. Sennichrast, who studied some of the species of Œcodoma in Mexico, is of the opinion that their special rôle, if they have one, is borne in the excavation of the nest, and in tunneling the galleries, labors which require superior strength and better implements.

The third order of workers is the most curious. If the main shaft of a mine be probed, a small number of colossal fellows (3, Fig. 1) will slowly begin to make their way up the smooth sides of the mine. In the middle of the forehead is a trim ocellus, or simple eye, of quite different structure from the ordinary compound eye on the sides of the