To an ant a tree is a forest in itself. Ascending its mammoth trunk to the upper regions, she follows the great highways of the branches, out into the unknown and trackless wilderness of leaves in pursuit of her game--the aphid. She knows well in what wild and solitary uplands to look for this mountain-goat.
The under side of maple leaves affords good pasturage to numerous green aphids which there browse contentedly in the pleasant shade and under the watchful eyes of the small brown ants that herd them. The aphids are all sizes and ages, though as to age the difference is probably but a few days. With a glass, the process of "milking" may be observed, the ants merely stroking the aphids with their antennæ. Two small tubes, like sap quills, protrude from the back of the aphid, and from time to time minute glistening drops are seen to exude from these tubes and are removed by the ants in attendance. Surely, to the ant here is the land of milk and honey. They move constantly to and fro among the aphids, now and then stopping to stroke one. Apparently they detect by some signs which are ready to yield the sweet fluid. Their presence appears to be agreeable to the aphids and is never in the least resented. After long watching with the glass, I have never seen anything akin to insubordination. Pluck the leaf ever so gently and hold it in a proper position, the difference is at once apparent to the aphids, for there begins an exodus, and large and small troop up the stem of the leaf and so on to whatsoever it may be attached; nor does it cease until they have deserted to the last one.
But the life of ants is by no means given over to these bucolic pursuits. While the meadow-ants seem to be in the pastoral stage, the red species and the large black ones are hunters and warriors. The most sanguinary conflict I have witnessed was a battle of the ants. Two armies of the same black species met on the floor of a neighbor's barn. The battle lasted throughout several days, and both sides fought with indescribable ferocity. Where they came from was a mystery, as no such colonies of ants had ever been seen thereabouts.
They appeared to be of the species _Formica pennsylvanica_ which nests in trees, but these do not occur in very large colonies, whereas the contending hosts upon the barn floor were as the Tartar hordes. The floor was strewn with struggling pairs and with the dead and injured, and always fresh forces were arriving.