The Speech of Monkeys

[Sidenote: A COLONY OF ANTS] I have observed that signs prevail to a great extent among ants. Some years ago I had an opportunity of studying a colony of ants, and I watched them almost daily for several weeks. I had seen it stated that they found their way by the sense of smell, but these observations confirmed my doubts on that point, and I feel justified in saying that they are guided almost, if not entirely, by landmarks. On the bark of a tree from which they were gathering in their winter stores, I observed that there were certain little knots or protuberances by which they directed their course and which they always passed in a certain order. Between these landmarks they did not confine themselves to any exact path, but the concourse would sometimes widen out over the space of more than an inch, but as they approached a landmark every ant fell into line and went in the exact path of the others, which rarely exceeded in any case more than an eighth of an inch in width. Whenever an ant would lose its way it would lift its head high into the air, look around, and then turn almost at right angles from the course it was pursuing towards the path of the others. In scores of cases I observed that the outward-bound ant, when it had been lost and returned to the path, always came on the homeward side of the landmark and passed out.