faceted or compound structure, such as are usual in insects, and which ordinary ants (Formica) are furnished with; but all are provided with organs of vision, composed each of a single lens. Connecting them with the utterly blind species of the genus, is a very stout-limbed Eciton, the E. crassicornis, whose eyes are sunk in deep sockets. This ant goes on foraging expeditions like the rest of its tribe, but it avoids the light, always moving in concealment under leaves and fallen branches. When its columns have to cross a cleared space, the ants construct a temporary covered way with granules of earth, arched over, and holding together mechanically; under this the procession passes in secret, the indefatigable creatures repairing their arcade as fast as breaches are made in it.
Next in order comes the E. vastator, which has no eyes, though the collapsed sockets are plainly visible; and, lastly, the E. erratica in which both sockets and eyes have disappeared, leaving only a faint ring to mark the place. The armies of E. vastator and E. erratica move wholly under covered roads, constructing them rapidly as they advance. The column of foragers pushes forward, step by step, under the protection of these covered ways, and, on reaching a rotten log, or other promising hunting-ground, pour into the crevices in search of booty. The grains of earth for their arcades are taken from the soil over which the column is passing, and are fitted together without cement.
Fig. 5.—Foraging-Ants (Eciton erratica), constructing a Covered Road—Soldiers sallying out on being disturbed.
Working in numbers, they build up simultaneously the sides of their convex arcades, and contrive in a surprising manner to approximate them and fit in the key-stone without letting the loose, uncemented structure fall to pieces. There is a very clear division of labor between the two classes of neuters in these blind species. When a breach is made in one of their covered ways, all the ants underneath are set in commotion, but the worker-minors remain behind to repair the damage, while the large-heads issue forth in a most menacing manner, rearing their heads, and snapping their jaws with an expres-
