Page:Popular Science Monthly Volume 19.djvu/845

Rh defending the working community (like soldier termites) against all comers. Whenever I made a breach in one of their covered ways, all the ants underneath were set in commotion, but the worker-miners remained behind to repair the damage, while the large-heads issued forth in a most menacing manner.

These two blind species of Eciton are particularly interesting from the fact that in a part of the world so remote from them as Western Africa there is another genus of military ant, also blind, which in all its habits closely resembles the blind Ecitons of Brazil. For, like the latter, Annornia arcens march in long, close columns through tunnels, have no fixed nest, but make temporary halts in shaded places, and are no less organized, remorseless, and irresistible than their American congeners. In one curious particular, however, they differ: the relative position of the marchers and the carriers is reversed, for here the carrier-columns occupy the middle place, while the marching columns with their officers occupy the flanks. When overtaken by a sudden African rain-storm, these ants congregate in a close mass, with the younger ants in the center; they thus form a floating island.

It is remarkable that ants of different hemispheres should manifest so close a similarity with respect to all these wonderful habits. The Chasseur ants of Trinidad, and, according to Madame Merian, the ants of Visitation of Cayenne, also display habits of the same kind.

—I shall conclude this brief résumé of the more important facts at present known concerning the psychology of ants with a few selected observations of the display of high intelligence. It is always difficult to draw the line between instinct and reason, between adjustive action due to hereditary or purposeless habit and adjustive action due to individual and purposive adaptation. But we may be least diffident in accepting as evidence of the latter cases where animals exhibit a power of adapting their actions to meet the requirements of novel circumstances or circumstances which can not be supposed to have been of sufficiently frequent occurrence in the life-history of the species to have developed instincts of mechanical response in the individual. It is in view of this consideration that the following instances are selected.

Ebrard records in his "Études de Mœurs" an observation of his own on F. fusca. The ants were engaged in building walls, and when the work was nearly completed there still remained an interspace of twelve or fifteen millimetres to be covered in. For a moment the ants were thrown out, and

seemed inclined to leave their work, but soon turned instead to a grass-plant growing near, the long, narrow leaves of which ran close together. They chose the nearest, and weighted its distal end with damp earth, until its apex just bent down to the space to be covered. Unfortunately, the bend was too close to the extremity, and it threatened to break. To prevent this misfortune the ants gnawed at the base of the leaf until it bent along its whole length and covered the space required. But, as this did not seem to be quite enough, they heaped