keep a few alive by themselves in captivity, and at any rate their habits under such circumstances are entirely altered. If, on the other hand, a whole community is kept, then the greater number introduces a fresh element of difficulty and complexity. Moreover, within the same species, the individuals seem to differ in character, and even the same individual will behave very differently under different circumstances. Although, then, ants have attracted the attention of many of the older naturalists,-Gould, De Geer, Reaumur, Swammerdam, Latreille, Leuwenhoeck, Huber,--and have recently been the object of interesting observations by Frederick Smith. Belt, Moggridge, Bates, Mayr, Emery, Forel, McCook, and others, they still present one of the most promising fields for observation and experiment.

The life of an ant falls into four well-marked periods-those of the egg, of the larva or grub, of the pupa or chrysalis, and of the perfect insect or imago. The eggs are white or yellowish, and somewhat elongated. They are said to hatch about fifteen days after being laid. Those observed by me have taken a month or six weeks.

The larvæ of ants (Pl. V. fig. 3), like those of bees and wasps, are small, white, legless grubs somewhat conical in form, being narrow towards the head. They are carefully tended and fed, being carried about from chamber to chamber by the workers, probably in order to secure the most suitable amount of warmth

and moisture. I have observed, also, that they are very often assorted according to age. It is sometimes very curious in my nests to see them arranged in groups according to size, so that they remind one of a school divided into five or six classes.

As regards the length of life of the larvæ, Forel supposed' that those of Tapinoma matured the quickest, and were full-grown in about six or seven weeks. Some of Myrmica ruginodis, however, observed by me, turned into pupa in less than a month. In other cases the period is much longer. In certain species, Lasius flavus, for instance, some of the larvæ live through the winter.

When full grown they turn into pupæ (Pl. V. fig. 4), sometimes naked, sometimes covered with a silken cocoon, constituting the so-called 'ant-eggs.' We do not yet understand why some larvæ spin cocoons, while others remain naked. As a general rule, the species which have not a sting, spin a cocoon, while those which have, are naked. Latreille was the first to observe that in one species (F. fusca) the pupæ sometimes spin a cocoon, and sometimes remain naked. The reason for this difference is still quite unknown. After remaining some days in this state they emerge as perfect insects In many cases, however, they would perish in the attempt, if they were not assisted; and it is very pretty to see the older ants helping them to extricate them

Les Fourmis de la Suisse, p. 420.

selves, carefully unfolding their legs and smoothing out the wings, with truly feminine tenderness and delicacy. Our countryman Gould was the first to observe, and the fact has since been fully confirmed by Forel, that the pupæ are unable to emerge from the cocoons without the assistance of the workers. The ants generally remain from three to four weeks in this condition.

In the case of ants, as with other insects which pass through similar metamorphoses, such as bees, wasps, moths, butterflies, flies, and beetles, &c., the larval stage is the period of growth. During the chrysalis stage, though immense changes take place, and the organs of the perfect insect are more or less rapidly developed, no food is taken, and there is no addition to the size or weight.

The imago or perfect insect again takes food, but does not grow. The ant, like all the insects above named, is as large when it emerges from the pupa as it ever will be; excepting, indeed, that the abdomen of the females sometimes increases in size from the development of the eggs.

We have hitherto very little information as to the length of life in ants in the imago, or perfect, state. So far, indeed, as the preparatory stages are concerned, there is little difficulty in approximately ascertaining the facts; namely, that while in summer they take only a few weeks; in some species, as our small yellow meadow ants, the autumn larvæ remain with compara

tively little change throughout the winter. It is much more difficult to ascertain the length of life of the perfect insect, on account of their gregarious habits, and the difficulty of recognising individual ants. I have found, however, as we shall presently see, that their life is much longer than has been generally supposed.

It is generally stated in entomological works that the males of ants die almost immediately. No doubt this is generally the case. At the same time, some males of Myrmica ruginodis, which I isolated with their mates in August 1876, lived until the following spring; one of them till May 17.

It has also been the general opinion that the females lived about a year. Christ' indeed thought they might last three or even four seasons, but this was merely a suggestion, and Forel expressed the general opinion when he said, 'Je suis persuadé qu'en automne il ne reste presque plus que les ouvrières écloses pendant le courant de l'été.' The average life of a queen is also, he thinks, not more than twelve months. I have found, however, that the life of the queens and workers is much longer than had been supposed. I shall give further details in a subsequent chapter, but I may just mention here that I kept a queen of Formica fusca from December 1874 till August 1888, when she must have been nearly fifteen years old, and of course may have been more. She 1 Naturgeschichte der Insekten.

attained, therefore, by far the greatest age of any insect on record. I have also some workers which I have had since 1875.

The body of an ant consists of three parts: the head, thorax, and abdomen. The head bears the principal organs of sense, and contains the brain, as the anterior portion of the nervous system may fairly be called. The thorax, supporting the legs and, when they are present, the wings, contains the principal muscles of locomotion. The abdomen contains the stomach and intestines, the organs of reproduction, the sting, &c.

Returning to the head: the antennæ consist of a short spherical basal piece, a long shaft, known as the scape, and a flagellum of from six to seventeen (generally, however, from ten to thirteen) short segments, the apical ones sometimes forming a sort of club. The number of segments is generally different in the males and females.

The eyes are of two kinds. Large compound eyes, one on each side of the head; and ocelli, or so-called simple eyes. The compound eyes consist of many facets. The number differs greatly in different species, and in the different sexes, the males generally having the greatest number. Thus, in Formica pratensis there are, according to Forel, in the males about 1,200 in each eye, in the fertile females between 800 and 900, in the workers about 600. Where the workers vary in size

1 Having reference to the facts stated on page 37, this is a result of great physiological interest.