Memory of Friends (Kindred).—This phase of mind in ants has been closely studied and graphically described by Sir John Lubbock. Most of his experiments and observations have been verified by myself, therefore the reader will pardon me if I quote freely from his valuable work, Ants, Bees, and Wasps.
The observations of Huber, Ford, Lubbock, and other observers declare that ants can remember and recognize their kindred after having been separated from them for several months. "Huber mentions that some ants which he had kept in captivity having accidentally escaped, met and recognized their former companions, fell to mutual caresses with their antennæ, took them up by their mandibles, and led them to their own nests; they came presently in a crowd to seek the fugitives under and about the artificial ant-hill, and even ventured to reach the bell-glass, where they effected a complete desertion by carrying away successively all the ants they found there. In a few days, the ruche was depopulated. These ants had remained four months without any communication."[36]
On one occasion, I took ten Lasius niger and confined them in a specially constructed formicary so that they could not possibly leave the nest. I supplied these colonists with a gravid queen, so they very quickly became satisfied with their new home. Four months thereafter, I put three of these ants, previously marked with a paint of zinc oxide and gum arabic, into their former nest. They were at once recognized by their kindred, which began to caress them with their antennæ and to remove the paint from their bodies. In the course of a half hour, the paint had all been removed, and I lost sight of them among the other ants.
A month after the performance of this experiment, I took three marked ants from the parent nest and placed them in the new nest. They were at once recognized by the colonists, which received them, as it were, with open arms and began to cleanse their bodies by removing the paint. In both of these experiments the recognition appeared to be instantaneous; there was no hesitancy whatever.
On the other hand, when performing like experiments with Lasius flavus, it took the ants (on two occasions) some little time to recognize their kindred; when the marked ants were put into the nest they were at once seized by the other ants, which pulled them about the nest for some time. They were finally recognized, however, and the paint removed from their bodies by the busy little tongues of their kindred.
This would seem to indicate that Lasius niger had a better memory than Lasius flavus; whether the failure of the latter to recognize their friends at once was due, however, to faulty memory or not, is a psychical problem that will, probably, never be solved.
Lubbock's experiments with Myrmica ruginodis clearly demonstrate that these ants can recognize their kin. Says he:—
"On August 20, 1875, I divided a colony of Myrmica ruginodis so that one half were in one nest, A, and the other half in another, B, and were kept entirely apart.
"On October 3, I put into nest B a stranger and an old companion from nest A. They were marked with a spot of color. One of them immediately flew at the stranger; of the friend they took no notice.
"October 18.—At 10 a.m. I put in a stranger and a friend from nest A. In the evening the former was killed, the latter was quite at home.