Brehm’s Thierleben is the great repository of facts concerning the social lives of the higher animals. The third edition, in ten large volumes, fully illustrated, and edited by Pechuel LÖsche, has lately appeared (Leipzig und Wien, Bibliog. Institute, 1890-92). It is, indeed, as Virchow has lately termed it, “a sort of zoological library,” popular in character, and almost purely descriptive. (There is a French edition of this work in nine volumes, but, with the exception of one fragment, it has not appeared in English. The nearest approach to Brehm’s work in England is Cassell’s New Natural History, and in America the Riverside Natural History.) It is impossible to enumerate the numberless works by travellers and others on which the knowledge of animal industries is founded. The works of Huber, Fabre, Audubon, Le Vaillant, C. St. John, Belt, Bates, Tennent, are frequently quoted in the course of this work. Many of the most important and detailed studies of animal industries are scattered through the pages of the scientific periodicals of all countries. References to a few of the chief of these studies will be found in the text.

For a scientific discussion of the phenomena of animal skill and intelligence we may perhaps best turn to Professor C. Lloyd Morgan, whose work is always both acute and cautious. In Animal Life and Intelligence (1890) he has furnished an excellent introduction to the subject. In his Introduction to Comparative Psychology (shortly to appear in the Contemporary Science Series) he discusses the fundamental problems of mental processes in animals, and the transition from animal intelligence to human intelligence. Romanes’ Mental Evolution in Animals (1883) and other works by this writer, dealing with the same subject, but proceeding on a different method, should also be studied; and his Animal Intelligence (International Science Series) is an excellent critical summary of the facts. BÜchner’s Aus dem Geistesleben der Thiere (Berlin, 1877) and Houzeau’s FacultÉs Mentales des Animaux (Brussels, 1877) may also be mentioned, and Espinas’ SociÉtÉs Animales (1877), though dealing primarily with sociology, is an original and suggestive study of great value.

As a general introduction, of a popular but not unscientific character, to all the various aspects of animal life, J. Arthur Thomson’s little book, The Study of Animal Life (University Extension Manuals, 1892), may be recommended. At the end of Mr. Thomson’s volume will be found a useful classified list of the “Best Books” on animal life.

Gardening Ants.

The operations of various species of Gardening Ants have recently been very thoroughly investigated at Blumenau by Herr Alfred MÖller, nephew of Dr. Fritz MÜller (“Die PilzgÄrten einiger sÜdamerikanischer Ameisen.” Heft 6 of Schimper’s “Botanische Mittheilungen aus den Tropen.” Jena: G. Fischer, 1893. Herr MÖller’s work is clearly summarised by Mr. John C. Willis in “The Fungus Gardens of certain South American Ants,” Nature, 24th August 1893).

The ants of Blumenau chiefly differ from those described by Belt in that they form very narrow streets, in which they travel only in single file, and also that their nests occur both in the forest and in the open. The commonest species is the Atta (Acromyrmex) discigera, Mayr, and the workers are never more than 6.5 mm. long. There are other species of Atta which have very similar streets; one, the Atta hystrix, Latr., appears to work only at night. A minute description is given of a street of A. discigera, which was 26 metres long and about 1.5 cm. wide and high, roofed in in parts wherever possible. It led to a number of small Cupheas, whose leaves the ants were cutting. In the street could be seen a procession of loaded ants going towards the nest, and others empty-handed, going in the opposite direction. Some of the large workers run up and down the road unloaded, and act as road-menders if any accident happens to a part of the track. Other very small workers, which do not cut leaves, may also be seen carried upon the backs or even upon the loads of the actual leaf-cutters. An ant carrying a peculiarly shaped piece of leaf was watched from end to end of the track, and travelled the 26 m. in 70 minutes. The load was twice as heavy as itself.

The plants attacked by the ants were found to be very numerous, and the ants seemed to be very capricious in this respect, one day stripping a plant and the next day leaving it untouched.

The jaws of the ants are very strong, with serrated edges, and clash together laterally. The ant begins at the edge of a leaf, and cuts out a piece in about five minutes, revolving on one of its hind legs as a centre. When the piece is almost freed, the ant goes on to the main portion of the leaf, cuts through the last piece uniting it with the severed portion, drags up the latter, balances it on edge between its forelegs, and then, grasping it with its jaws, lifts it up above its head, so that the centre of gravity of the load is above the ant itself. It then marches off, down the stem, to the base, over the ground to the end of the street, and along this to the nest, travelling at a very uniform speed, and never letting go its load. The weight thus carried was found, on an average, to be twice that of the ant; but many were found carrying heavier loads, even as much as ten times their own weight!

The nests are usually below the surface of the soil, but covered, wherever necessary, with a thick mass of withered pieces of leaves and twigs, etc. They may be as much as 1-1/2 metres in diameter. In the nests of all species examined there is found, filling up the interior, a curious grey spongy mass, full of chambers, like a coarse sponge, in which the ants may be seen running about, and in which, here and there, occur eggs, larvÆ, and pupÆ. This is the fungus garden. It is separated from the roof and lateral walls of the nest by a clear space. The walls and roof are much thicker in winter than in summer; one nest examined had a roof 25 cm. thick and wall 40 cm. The garden consists of two parts, differently coloured, but not very sharply marked off from each other. The older part is yellowish-red in colour; the newly-built portions, forming the surface of the garden, are of a blue-black colour. It is this part which is of the greater importance to the ants.

The garden is found, on examination, to consist of an immense conglomeration of small round particles of not more than .5 mm. in diameter, of a dark green colour when quite fresh, then blue-black, and finally yellowish-red. They are penetrated by, and enveloped in, white fungus hyphÆ, which hold the particles together. These hyphÆ are similar throughout the nest.

Strewn thickly upon the surface of the garden are seen round white bodies about .25 mm. in diameter; they always occur in the nests, except in the very young portion of the gardens. They consist of aggregations of peculiar swollen hyphÆ, and are termed by MÖller the “Kohl-rabi clumps.” The hyphÆ swell out at the ends into large spherical thickenings, filled with richly vacuolated protoplasm like the ordinary hyphÆ. These clumps of “Kohl-rabi” are only found on the surface of the garden, and form the principal food of the ants; they have no doubt reached their present form under the cultivation and selection of the ants. The fungus was found to belong to the genus Rozites, and the species was named R. gongylophora. A microscopic examination of the particles of which the garden is composed shows that they contain remains of leaves; bits of epidermis, stomata, spiral vessels, etc., occur in them.

If a nest is broken into and the fungus garden scattered, the ants collect it as quickly as possible, especially the younger parts, taking as much trouble over it as over the larvÆ. They also cover it up again as soon as possible to protect it from the light. A nest, 1 metre × 50 cm., was opened, and in twenty-four hours the ants had put on a new roof 10 cm. deep.

Some ants’ nests were placed under a bell jar and supplied with leaves; they made no use of them and presently died. If they were supplied with a piece of “garden,” they rebuilt it and covered it so far as they could. It was seen to shrink from day to day, the ants bringing out the old pieces and adding them to the wall; finally it was exhausted and the ants died. Others were starved for five days, and then supplied with a bit of garden; they at once began to eat the Kohl-rabi clumps. Finally, by supplying the ants with bits of garden, a damp sandy floor, and fresh leaves, they were induced to build in captivity. The dish in which they worked was covered by a glass lid, and when this was covered with a dark cloth or otherwise kept dark, the ants built under it without covering the garden. In this way the whole process was observed. An ant bringing in a piece of leaf proceeds to cut it into halves, repeating the process till it has got a very small piece left, which it holds between its fore feet and turns round, crushing it in its jaws until the whole is reduced to a round ball of pulp about .25 mm. thick. This it then takes and adds to the garden. So well is the kneading performed that no single cell remains uninjured, and it was observed that the hyphÆ of the fungus grew through and round one of these particles within a few hours. Belt supposed that this process was performed by the small workers above-mentioned, but it is not so, as we have just seen. The small workers perform the function of weeding the garden, and this is so well done that a portion of it removed and grown in a nutrient solution gives a perfectly pure culture, not even containing bacteria!

In the course of these investigations it was found that somewhat similar fungus gardens occur in the nests of the hairy ant, Apterostigma, but the fungus appeared to belong to a different genus, and the hairy ants, who live in decaying wood and have small gardens built of bits of wood-fibre, beetle-dung, etc., have not succeeded in cultivating and selecting Kohl-rabi to the same high degree. An allied genus of ants, Cyphomyrmex, were also found to be fungus-growers.

This elaborate study, which is illustrated by beautiful plates and photographs of the mushroom gardens, constitutes, as Mr. Willis (whose summary has here been followed) remarks, one of the most fascinating contributions to our knowledge of mycology and of animal industries which have been made for many years.