A drop of honey, or something like it, is the connecting bond between the ant and the Aphis. It is exuded by the latter through certain tubercles which are situated at the end of the abdomen, and is, of course, the product of the endless quantities of sap, which, so long as it lasts, these insects are for ever pumping up from the plant they inhabit, and swallowing. This honey, or honey-dew, to use the more special name bestowed on it, the ants want, but they are not content with drinking it whenever it issues from its manufacturers, in natural course. This is not sufficient, and they have learned to increase the flow of so valued a beverage by their own efforts—in other words, they milk the Aphides, which thus become their cows. To do this they tap them with their antennæ, softly and gently, on the sides of the abdomen—a quick little shower of touches. Under the influence of this probably pleasant sensation the Aphis becomes willing to part, and, raising the abdomen, “teems her refreshing dew” in a drop from the tip of it. This action of the ants cannot, in Europe, be successfully imitated, at least it has not been, and if an ant is not forthcoming the fluid is contained in the body of the Aphis until necessity compels its being ejected. Probably the ants, if delayed in their visits, are missed by the Aphides, as a cow misses her milker, and long before they do excrete, as the process is called, they would perhaps have done so had they felt able. The sensation no doubt of the ant’s antennæ on the abdomen has become, through usage, the almost necessary stimulus to the act produced by it.