Büchner, in his recently published and translated work on "Mind in Animals," gives a singular observation analogous to the above, which was communicated to him by Herr G. Theuerkauf. A maple tree standing in the grounds of Herr Vollbaum, of Elbing, swarmed with ants and aphides. In order to check the mischief, the proprietor smeared about a foot width of the ground around the tree with tar. The first ants that arrived stuck fast; but the next, seeing the predicament of their companions, turned back and fetched a number of aphides from the tree, which they stuck down on the tar one after another till they had made a bridge over which they could cross without danger.
It will be observed that all these cases, being so analogous although recorded independently by different observers, serve to corroborate one another. As such corroboration in matters of this kind is of value, I shall here add two or three cases which go to confirm the observation of Cardinal Fleury regarding the construction of a floating bridge. Dr. Ellendorf writes to Professor Büchner that he protected a cupboard of his provisions from the invasion of ants by standing the legs of the cupboard in saucers filled with water. He adds:
I myself did this, but I none the less found thousands of ants in the cupboard next morning. It was a puzzle to me how they crossed the water, but the puzzle was soon solved. For I found a straw in one of the saucers. . . . This they had used as a bridge. . . . I pushed the straw about an inch from the cupboard-leg, when a terrible confusion arose. In a moment the leg immediately over the water was covered with hundreds of ants feeling for the bridge in every direction with their antennæ, running back again and coming in ever larger swarms, as though they had communicated to their companions within the cupboard the fearful misfortune that had taken place. Meanwhile the new-comers continued to run along the straw, and, not finding the leg of the cupboard, the greatest perplexity arose. They hurried along the edge of the saucer, and soon found where the fault lay. With united forces they pulled and pushed at the straw, until it again came into contact with the wood, and the communication was again restored.
The military ants, both in America and Africa, exhibit still more extraordinary resources in the way of bridge-making. Thus Belt says of the Ecitons:
I once saw a wide column trying to pass along a crumbling, nearly perpendicular, slope. They would have got very slowly over it, and many of them would have fallen; but a number having secured their hold, and reaching to each other, remained stationary, and over them the main column passed. Another time they were crossing a water-course along a small branch, not thicker than a goose-quill. They widened this natural bridge to three times its width by a number of ants clinging to it and to each other on each side, over which the column passed three or four deep; whereas, excepting for this expedient, they would have had to pass over in single file, and treble the time would have been consumed.
