McCook's account whether he himself witnessed the facts. The facts, however, which he narrates, are that a peach-tree having grown up so as to overshadow a nest of harvesting ants, the latter climbed the tree to strip off the leaves. "I am convinced," says McCook, "that the reason for this onslaught was the desire to be rid of the obnoxious shade." If this statement had been met with in any ordinary book on animal intelligence, of course I should not have quoted it; but as McCook went to Texas for the express purpose of studying these ants in a scientific manner, and as the numerous other observations which he made, both on these and on the mound-building species, entitle him to respect, I have not felt justified in suppressing this statement.
The observation made by Colonel Sykes on certain ants in India has gained a wide notoriety from its having been published by Spence in his popular work on instinct. Colonel Sykes was a good observer, so that his account ought not to be questioned. He says that in order to guard his provisions from the ants he put them on a table, the four legs of which he placed in as many basins filled with water. Some ants still succeeded in scrambling across the water, and so the legs of the table were likewise painted with turpentine. The ants then ran up a wall near which the table stood, and when about a foot above its level, they sprang from the wall to the table.
Somewhat analogous to this is the observation of Professor Leuckhart, who placed round the trunk of a tree, which had been visited by ants as a pasture for aphides, a broad cloth soaked in tobacco-water. When the ants, returning home down the trunk of the tree, arrived at the soaked cloth, they turned round, went up the tree again to some of the overhanging branches, and allowed themselves to drop clear of the obnoxious barrier. On the other hand, the ants which desired to mount the tree first examined the nature of the obstruction, then turned back and procured some pellets of earth, which they carried in their jaws and deposited, one after another, upon the cloth till a harmless road of earth was made across it.
This observation of Professor Leuckhart is in turn a corroboration of an almost identical one made more than a century ago by Cardinal Fleury, and communicated by him to Réaumur, who published it in his "Natural History of Insects" (1734). The Cardinal smeared the trunk of a tree with bird-lime, in order to prevent the ants from ascending it; but the insects overcame the obstacle by making a road of earth, small stones, etc., as in the case just mentioned. On another occasion the Cardinal saw a number of ants make a bridge across a vessel of water surrounding the bottom of an orange-tree tub. They did so by conveying a number of little pieces of wood, the choice of that material, instead of earth or stones, as in the previous case, apparently betokening no small knowledge of practical engineering—a knowledge which, as we shall presently see, is also shared by the Ecitons.