I then placed a heap of fine mould close to the grass, but just so far that they could still not reach across. It would have been of course quite easy for any ant, by moving a particle of earth for a quarter of an inch, to have made a bridge by which the food might have been reached, but this simple expedient did not occur to them. On the other hand, I then put some provisions in a shallow box with a glass top, and a single hole on one side, and put some specimens of Lasius niger to the food. As soon as a stream of ants was at work, busily carrying supplies off to the nest, and when they had got to know the way thoroughly, I poured some fine mould in front of the hole so as to cover it up to a depth of about half an inch. I then took out the ants which were actually in the box. As soon as they had recovered from the shock of this unexpected proceeding on my part, they began to run all around and about the box, looking for some other place of entrance. Finding none, however, they began digging down into the earth just over the hole, carrying off the grains of earth one by one, and depositing them, without any order, all round at a distance of from half an inch to six inches, until they had excavated down to the doorway, when they again began carrying off the food as before. This experiment I repeated on the following days three or four times, always with the same result.
As evidence both of their intelligence and of their affection for their friends, it has been said by various observers that when ants have been accidentally buried they have been very soon dug out and rescued by their companions. Without for a moment doubting the facts as stated, we must remember the habits which ants have of burrowing in loose fresh soil, and especially their practice of digging out fresh galleries when their nests are disturbed. It seemed to me, however, that it would not be difficult to test whether the excavations made by ants under the circumstances were the result of this general habit, or really due to a desire to extricate their friends. With this view I tried (20th of August) the following experiments: I placed some honey near a nest of Lasius niger on a glass surrounded with water, and so arranged that in reaching it the ants passed over another glass covered with a layer of sifted earth about one-third of an inch in thickness. I then put some ants to the honey, and by degrees a considerable number collected round it. Then, at 1.30 p. m., I buried an ant from the same nest under the earth, and left her there till 5 p. m., when I uncovered her. She was none the worse, but during the whole time not one of her friends had taken the least notice of her.
Again, September 1st, I arranged some honey in the same way. At 5 p. m. about fifty ants were at the honey, and a considerable number were passing to and fro. I then buried an ant as before, of course taking one from the same nest. At 7 p. m. the number of ants at the honey had nearly doubled. At 10 p. m. they were still