edge respecting the habit in question, as practiced by a certain species of ant (Lasius flavus), which departs in a somewhat remarkable manner from the habit as practiced by other species. He says: "When my eggs hatched I naturally thought that the aphides belonged to one of the species usually found on the roots of plants in the nests of Lasius flavus. To my surprise, however, the young creatures made the best of their way out of the nest, and, indeed, were sometimes brought out of the nest by the ants themselves." Subsequent observation showed that these aphides, born from eggs hatched in the ants' nest, left the nest, or were taken from it, as soon as they were hatched, in order to live upon a kind of daisy which grew around the nest. Sir John then made out the whole case to be as follows:
As a supplement to this interesting observation, I may here append the following, which is due to Herr Nottebohm, who communicated it to Professor Büchner: This gentleman had a weeping-ash which was covered by millions of aphides. To save the tree, he one day in March cleaned and washed every branch and spray before the buds had burst, so removing all the aphides. There was no sign of the latter till the beginning of June, when he was surprised one fine sunny morning to see a number of ants running quickly up and down the trunk of the tree, each carrying up a single aphis to deposit it on the leaves, when it hurried back to fetch another. "After some weeks the evil was as great as ever. . . . I had destroyed one colony, but the ants replanted it by bringing new colonists from distant trees and setting them on the young leaves."
Aphides are not the only insects which are utilized by ants as cows. Gall-insects and cocci are kept in just the same way; but McCook observed that, where aphides and cocci are kept by the same ants, they are kept in separate chambers, or stalls. Caterpillars of the genus Lycæna have also been observed to be kept by ants for the sake of a sweet secretion which they supply.
Slavery.—The habit or instinct of keeping slaves obtains at least among three species of ant. It was first observed by P. Huber in Formica rufescens, which enslaves the species F. fusca, the members of which are appropriately colored black. The slave-making ants