an ant’s nest the same restless activity of the workers, the same earnest attention paid to the young and pupae, the same instinct in shielding the young from danger, and much the same general routine of development.  Certain rather special, and it may be said extraordinary, habits of ants may, however, demand notice before we attempt a brief survey of their instincts at large.  Few readers are unacquainted with the Aphides, or plant-lice, those little wingless insects which infest our plants and herbs in myriads in summer.  It is a fact now well known to naturalists, and first placed on record by Huber, that between the ants and plant-lice, relations of a very friendly and, as far as the ants are concerned, advantageous character have become established.  Ants have been observed to stroke the tips of the bodies of the plant-lice with their antennae, this act causing the plant-lice to exude drops of a clear, sweet fluid, of which the ants are extremely enamoured.  The ants would thus appear to habitually “milk” their insect-neighbors, and, as far as observation goes, some ants seem not merely to keep the plant-lice in their nests so as to form a veritable dairy establishment, but also to make provision in the future by securing the eggs of the aphides, and bringing up the young as we rear calves.

[Illustration:  FIG 4.  APPLE APHIS (Eriosoma Mali).]

That the relation between the ants and plant-lice are of very stable kind is proved by the interesting remarks of Mr. Darwin, who “removed all the ants from a group of about a dozen aphides on a dock-plant, and prevented their attendance during several hours.”  Careful watching showed that the plant-lice after this interval did not excrete the sweet fluid.  Mr. Darwin then stroked the plant-lice with a hair, endeavoring thus to imitate the action of the ant’s feelers, but not a single plant-louse seemed disposed to emit the secretion.  Thereafter a single ant was admitted to their company, the insect, in Mr. Darwin’s words, appearing, “by its eager way of running about, to be well aware what a rich flock it had discovered.”  The ant first stroked one aphis and then another, each insect excreting a drop of the sweet juice “as soon as it felt the antennae;” and “even the quite young aphides behaved in this manner, showing that the action was instinctive, and not the result of experience.”  If, as Mr. Darwin remarks, it is a convenience for the aphides to have the sweet secretion removed, and that “they do not excrete solely for the food of the ants,” the observation does not in any degree lessen the curious nature of the relationship which has become established between the ants and their neighbors, or the interesting features in ant life which have inaugurated and perpetuated the habit.