[Illustration: FIG. 60.—An ant “milking” a “plant-louse” or “green-fly” for honey-dew. The drop of honey-dew is seen exuding from one of the two long tubes or spouts (called “cornicles”) on the back of the plant-louse at _a_. These spouts are seen at the hinder part of the body in the drawings of the hop-louse (Figs. 55 to 59). The ant is causing the aphis to pour out its honey-dew (in fact “milking” it) by “drumming” on the body of the plant-louse with its clubbed antennæ, and has taken the drop of honey-dew between its jaws. This drawing was made from life by the late Mr. Buckton, F.R.S., a great student of these creatures. The ant is that kind known as _Myrinica rubra_. The plant-louse is the _Aphis sambuci_ or blight of the elder-tree.] Another curious production of the aphides—common on the leaves of elms and other trees infested by them—is known as “honey-dew.” It is sticky and sweet, and was supposed by old writers to have distilled from the stars, or otherwise to have dropped from heaven. It is this sweet secretion which has led to the establishment of a most curious friendship between ants and aphides, or plant-lice. It has long been known that an ant will approach an aphis, and tickle it, when at once the aphis exudes from its cornicles (see Fig. 60) a drop of sweet honey-dew, which the ant swallows—just as a man may milk a cow and drink the milk. And the resemblance goes further, for the ants take possession of certain aphides, and keep them either underground or in specially constructed chambers, where they can gain ready access to them and “milk” them for honey-dew. There has been a certain amount of exaggeration in the description of these facts by some of the older writers; but it is undoubtedly true that some species of ants keep special flocks or herds of aphides, and feed on their sweet secretion.