that each nest had a sign or password. This was, for instance, the opinion of Gélieu, who believed that in each hive the bees had some common sign or password. As evidence of this, he mentions' that one of his hives had been for some days robbed by the bees from another: 'et je désespérais de conserver cet essaim, lorsqu'un jour, sur le soir, je le vis fort inquiet, fort agité, comme s'il eût perdu sa reine. Les abeilles couraient en tout sens sur le devant et le tablier de la ruche, se flairant, se tâtant mutuellement, comme si elles eussent voulu se dire quelque chose. C'était pour changer leur signe de reconnaissance, qu'elles changèrent en effet pendant la nuit. Toutes les pillardes qui

revinrent le lendemain, furent arrêtées et tuées. Plusieurs échappèrent aux gardes vigilantes qui défendaient l'entrée avertirent sans doute les autres du danger qu'elles avaient couru, et que l'on ne pouvait plus piller impunément. Aucune de celles qui voulurent. recommencer leur déprédation ne pénétra dans la ruche, dont elles avaient fait leur proie, et qui prospéra merveilleusement.'

Dujardin doubts the explanation given by Gélieu. He thinks that the nest which was robbed was at that time queenless, and that the sudden change in the behaviour of the bees was due to their having acquired

a queen.

Burmeister, on the contrary, in his excellent 'Manual of Entomology,' says that the power of com. Le Conservateur des Abeilles, p. 143.

municating to their comrades what they purpose is peculiar to insects. Much has been talked of the so-called signs of recognition in bees, which is said to consist in recognising their comrades of the same hive by means of peculiar signs. This sign serves to prevent any strange bee from entering into the same hive without being immediately detected and killed. It, however, sometimes happens that several hives have the same signs, when their several members rob each other with impunity. In these cases the bees whose hive suffers most alter their signs, and then can immediately detect their enemy.''

Others, again, have supposed ants recognise one another by smell.

Mr. McCook states that ants more or less soaked in water are no longer recognised by their friends, but, on the contrary, are attacked. Describing the following observation, he says: 2 I was accidentally set upon the track of an interesting discovery. An ant fell into a box containing water placed at the foot of a tree. She remained in the liquid several moments and crept out. Immediately she was seized in a hostile manner, first by one, then another, then by a third: the two antennæ and one leg were thus held. A fourth ant assaulted the middle thorax and petiole. The poor little bather was thus dragged helplessly to and fro for a long time, and was evidently ordained to death.

'Burmeister's Entomology, p. 502.

• Mound-making Ants of the Alleghanies, p. 280.

Presently I took up the struggling heap. Two of the assailants kept their hold; one finally dropped, the other I could not tear loose, and so put the pair back upon the tree, leaving the doomed immersionist to her hard fate.'

After recording one or two other similar observations, he adds: ''The conclusion, therefore, seems warranted that the peculiar odour or condition by which the ants recognise each other was temporarily destroyed by the bath, and the individuals thus "tainted" were held to be intruders, alien and enemy. This conclusion is certainly unfavourable to the theory that any thing like an intelligent social sentiment exists among the ants. The recognition of their fellows is reduced to a mere matter of physical sensation or "smell." This conclusion does not, I confess, seem to me to be conclusively established.

We can hardly suppose that each ant has a peculiar odour, and it seems almost equally difficult, considering the immense number of ants' nests, to suppose that each community has a separate and peculiar smell. Moreover, in a previous chapter I have recorded some experiments made with intoxicated ants. It will be remembered that my ants are allowed to range over a table surrounded by a moat of water. Now, as already mentioned, out of forty-one intoxicated friends, thirtytwo were carried into the nest and nine were thrown into the water; while out of fifty-two intoxicated

` Mound-making Ants of the Alleghanies, p. 281.

strangers two were taken into the nest and fifty were thrown into the water. I think it most probable that

even these two were subsequently brought out and 'treated like the rest.

It is clear, therefore, that in these species, and I believe in most, if not all others, the ants of a community all recognise one another. The whole question is full of difficulty. It occurred to me, however, that experiments with pupæ might throw some light on the subject. Although all the communities are deadly enemies, still if larvæ or pupæ from one nest are transferred to another, they are tended with apparently as much care as if they really belonged to the nest. In ant-warfare, though sex is no protection, the young are spared, at least when they belong to the same species. Moreover, though the habits of ants are greatly changed if they are taken away from their nest and kept with only a few friends, still, under such circumstances, they will carefully tend any young who may be confided to them. Now if the recognition were individual-if the ants knew any one of their comrades, as we know our friends, not only from strangers, but from one another -then young ants taken from the nest as pupae and restored after they had come to maturity would not be recognised as friends. On the other hand, if the recognition were effected by means of some signal or password, then the pupa which were intrusted to ants from another nest would have the password, if any, of that nest; and not of their own. Hence in this case

they would be amicably received in the nest from which their nurses had been taken, but not in their

own.

In the first place, therefore, I put, on September 2, 1877, some pupa from one of my nests of Formica fusca with a couple of ants from the same nest. On the 27th I put two ants, which in the meantime had emerged from one of these pupæ, back into their own nest at 8.30 A.M., marking them with paint as usual. At 9 they seemed quite at home; at 9.30, ditto; at 10, ditto; and they were nearly cleaned. After that I could not distinguish them.

On the 29th another ant came out of the pupastate; and on October 1 at 7.45 I put her back into the nest. She seemed quite at home, and the others soon began to clean her. We watched her from time to time, and she was not attacked; but, the colour being removed, we could not recognise her after 9.30.

On July 14 last year (1878) I put into a small glass some pupæ from another nest of Formica fusca with two friends.

On August 11 I put four of the young ants which had emerged from these pupa into the nest. After the interval of an hour, I looked for them in vain. The door of the nest was closed with cotton-wool; so that they could not have come out; and if any were being attacked, I think we must have seen it. I believe, therefore, that in the meantime they had been cleaned. Still, as we did not actually watch them, I