The Industries of Animals Part 6

[110] Bendire, Life Histories of North American Birds, 1892, p. 301.

Separation of females while brooding.--The Hornbill of Malacca[111] a.s.sures the protection of its nest and of the female while she is brooding in a singular manner. She lays in the hollow of a tree; as soon as she begins to sit on her eggs, the male closes the opening with diluted clay, only leaving a hole through which the captive can pa.s.s her beak to receive the fruits which he brings her in abundance. If the lady is thus cloistered as closely as in the most jealous harem, her lord and master at least expends on her the most attentive cares.

[111] Bernstein, "Ueber Nester und Eier einiger Javaschen Vogel," Cabani's Journ. f. Ornith., 1859.

What can be the object of this strange custom? It has been a.s.serted that during incubation the female loses her feathers and becomes unable to fly. The male would thus only wall her up as a precaution for fear of seeing her fall from the nest; because if this deplorable accident happened she would not be able to get back again. It seems to me that the effect is here taken for the cause, and that the falling off of feathers and torpidity must be the result rather than the motive of cloistration. One is tempted to believe that the male desires by this method to guarantee his female and her offspring against the attacks of squirrels or rapacious birds.Hygienic measures of Bees.--Among the animals who expend industry on hygiene and the protection of their dwellings, we must place Bees in the first line.

It may happen that mice, snakes, and moths may find their way into a hive.

a.s.saulted by the swarm, and riddled with stings, they die without being able to escape. These great corpses cannot be dragged out by the Hymenoptera, and their putrefaction threatens to cause disease. To remedy this scourge the insects immediately cover them with propolis--that is to say, the paste which they manufacture from the resin of poplars, birches, and pines. The corpse thus sheltered from contact with the air does not putrefy. In other respects Bees are very careful about the cleanliness of their dwellings; they remove with care and throw outside dust, mud, and sawdust which may be found there. Bees are careful also not to defile their hives with excrement, as Kirby noted; they go aside to expel their excretions, and in winter, when prevented by extreme cold or the closing of the hive from going out for this purpose, their bodies become so swollen from retention of faeces that when at last able to go out they fall to the ground and perish. Buchner records the observations of a friend of his during a season in which a severe epidemic of dysentery had broken out among the bees, which interfered with the usual habits of the insects; on careful examination of a hive it was found that a cavity in the posterior wall of the hive, containing crumbled clay, had been used as an earth closet. Many mammals are equally careful in this respect; thus, for example, the Beaver, as Hearne observed, always enters the water, or goes out on the ice, to urinate or defaecate; the faeces float and are soon disintegrated.

Animals are also careful about aeration. Thus, among Bees, in a hive full of very active insects the heat rises considerably and the air is vitiated. A service for aeration is organised. Bees ranged in files one above the other in the interior agitate their wings with a feverish movement; this movement causes a current of air which can be felt by holding the hand before the opening of the hive. When the workers of the corps are fatigued, comrades who have been resting come to take their place. These acts are not the result of a stupid instinct which the Hymenoptera obey without understanding. If we place a swarm, as Huber did, in a roomy position where there is plenty of air, they do not devote themselves to an aimless exercise. This only takes place in the narrow dwellings which Man grants to his winged guests.

The attention of Ants to public hygiene is more than equalled by their attention to personal hygiene. Without going into the question of their athletic exercises, which have attracted considerable attention, it is sufficient to quote one observeras to their habits of cleanliness. McCook remarks:--"The Agricultural Ants--and the remark applies to all other Ants of which I have knowledge--is one of the neatest of creatures in her personal habits. I think I have never seen one of my imprisoned harvesters, either Barbatus or Crudelis, in an untidy condition. They issue from their burrows, after the most active digging, even when the earth is damp, without being perceptibly soiled. Such minute particles of dust as cling to the body are carefully removed. Indeed, the whole body is frequently and thoroughly cleansed, a duty which is habitually, I might almost venture to say invariably, attended to after eating and after sleep. In this process the Ants a.s.sist one another; and it is an exceedingly interesting sight which is presented to the observer when this general 'was.h.i.+ng up' is in progress."[112]

[112] H. C. McCook, Agricultural Ants of Texas, 1879, chapter on "Toilet, Sleeping, and Funeral Habits," p. 125.

Prudence of Bees.--Certain species exhibit very great prudence, especially the Melipona geniculata, which lives in a wild state in South America. They place their combs in the hollow of a tree or the cleft of a rock; they fill up all the crevices and only leave a round hole for entry. And even this they are accustomed to close every evening by a small part.i.tion, which they remove in the morning. This door is shut with various materials, such as resin or even clay, which the bees bring on their legs as those of our own country bring pollen.

All these facts were observed with great exactness in a swarm given in 1874 by M. Drory (who during a long period of years studied every Brazilian species of Melipona at Bordeaux) to the Jardin d'Acclimatation. It was even seen that the door might be put up under certain circ.u.mstances in open day, as for example, when a storm or sudden cold delays the appearance of the workers. If one of them happened to be late it had to perforate the part.i.tion, and the hole was then stopped up again.

[Ill.u.s.tration: FIG. 42.]

Fortifications of Bees.--As these facts take place always they may be called instinctive; but that is not the case with regard to defences elevated with a view to a particular circ.u.mstance, and which disappear when the danger to which they correspond disappears. Such are the labours of the bees to repel the invasions of the large nocturnal Death's-head Moth. (Fig. 42.) He is very greedy of honey, and furtively introduces himself into the hives. Protected by the long and fluffy hairswhich cover him, he has little to fear from stings, and gorges himself with the greatest freedom on the stores of the swarm. Huber, in his admirable investigations,[113] narrates that one year in Switzerland numbers of hives were emptied, and contained no more honey in summer than in the spring. During that year Death's-head Moths were very numerous. The ill.u.s.trious naturalist soon became certain that this moth was guilty of the thefts in question. While he was reflecting as to what should be done, the bees, who were more directly interested, had invented several different methods of procedure. Some closed the entrance with wax, leaving only a narrow opening through which the great robber could not penetrate. Others built up before the opening a series of parallel walls, leaving between them a zigzag corridor through which the Hymenoptera themselves were able to enter. But the intruder was much too long to perform this exercise successfully. Man utilises defences of this kind; it is thus at the entrance of a field, for example, he places a turnstile, or parallel bars that do not face each other; the pa.s.sage is not closed for him, but a cow is too long to overcome the obstacle. In years when the Death's-head Moth is rare the bees do not set up these barricades, which, indeed, they themselves find troublesome. For two or three consecutive years they leave their doors wide open. Then another invasion occurs, and they immediately close the openings. It cannot be denied that in these cases their acts agree with circ.u.mstances that are not habitual.[114]

[113] Huber, Nouvelles observations sur les Abeilles.

[114] These facts have recently been observed and recorded afresh by Mr.

Clifford in Nature Notes, January 1893.

Precautions against inquisitiveness.--I will finally quote a fact of defence which took place under circ.u.mstances that were absolutely exceptional, and which therefore exhibits genuine reflection in these insects. During the first exhibition of 1855 an artificial hive was set up, one face of which was closed by a gla.s.s pane.

A wooden shutter concealed this pane, but pa.s.sers-by opened it every moment to contemplate the work of the small insects. Annoyed by this inquisitiveness, the bees resolved to put an end to it, and cemented the shutter with propolis. When this substance dried it was no longer possible to open the shutter. The bees were visible to n.o.body.

[Ill.u.s.tration: FIG. 43.]

[Ill.u.s.tration: FIG. 44.]Lighting up the nests.--An improvement of another nature in the comfort of the dwelling is introduced by the Baya, and if the facts narrated are correct they are the most marvellous of all. It is a question of lighting up a nest by means of Glow-worms. The Melicourvis baya inhabits India; it is a small bird related to the Loxia, already spoken of in this book. Like the latter it constructs a nest that is very well designed and executed. (Fig. 43.) It suspends it in general from a palm tree, but sometimes also from the roofs of houses. In these shelters, woven with extreme art, are always to be found little b.a.l.l.s of dry and hardened clay. Why does the bird ama.s.s these objects? Is it impelled by a collector's instinct less perfect than that of the Bower-bird? There is no reason to suppose this. Nor does it appear that he wishes to make the nest heavier and prevent it by this ballast from being blown about by every breeze when the couple are out, and the young not heavy enough to ensure the stability of the edifice. The part played by these little b.a.l.l.s is much more remarkable, if we may trust the evidence of the natives, as confirmed by competent European observers. Thus Mr. H. A. Severn writes:--"I have been informed on safe authority that the Indian Bottle-bird protects his nest at night by sticking several of these glow-beetles around the entrance by means of clay; and only a few days back an intimate friend of my own was watching three rats on a roof-rafter of his bungalow when a glow-fly lodged very close to them; the rats immediately scampered off."[115] These observations are confirmed by Captain Briant, as reported by Professor R.

Dubois.[116] In tropical regions luminous insects give out a brilliant light, of which the Glow-worms of northern countries can only give a feeble idea. These flying or climbing stars are the constellations of virgin forests. In South America the Indians utilise one of these insects, the Cucujo, by fastening it to the great toe like a little lantern, and profit by its light to find their road or to preserve their naked feet from snakes. The first missionaries to the Antilles, lacking oil for their lamps, sometimes replaced them by Fire-flies to read matins by.[117] The Melicourvis baya had already discovered this method of lighting, and the mysterious little b.a.l.l.s of clay were nothing more than candlesticks in which these birds set Glow-worms, when they are fresh, to act as candles. The entrance to the nest is thus luminous. (Fig. 44.) Apparently this lighting up is a defensive measure, for the birds have nothing to do at night except to sleep, and must be rather incommoded than cheered by this light. But the terrible enemy of all broods, the Snake, is, it is said, frightened by this illumination, which is able to penetrate the meshes of the nest, and will not dare to enter. The system is ingenious, and the Roman Emperors, when they used burning Christians as torches, were only plagiarising from this little bird, which paves with martyrs the threshold of its house of love.[115] "Notes on the Indian Glow-fly," Nature, 23rd June 1881.

[116] Science et Nature, t. iv. (1885), No. 94, p. 232.

[117] P. Dutertre, Hist. des Antilles francaise, 1667.CHAPTER VIII.

CONCLUSION.

DEGREE OF PERFECTION IN INDUSTRY INDEPENDENT OF ZOOLOGICAL SUPERIORITY--MENTAL FACULTIES OF THE LOWER ANIMALS OF LIKE NATURE TO MAN'S.

Degree of perfection in industry independent of zoological superiority.--As the result of our study we see the fundamental industries of Man dispersed throughout the animal kingdom, though not, indeed, all of them, nor the more subtle, which were only born yesterday. We may remark the extent to which intellectual manifestations of this sort are independent of the more or less elevated rank a.s.signed to species in zoological cla.s.sification. The latter, as it should be, brings together or separates beings according to their physical character. But intelligence does not depend on the whole body; its superior or inferior development is related to a certain corresponding complexity in the surface, volume, and histologic structure of the nervous centres.

It happens with the cerebral as with the other functions. An animal's superiority is not exhibited in all his organs nor in all his qualities; it results from a certain grouping of characters in which there may be weak points. The highest in organisation are not necessarily the swiftest or the strongest, any more than they are necessarily the most intelligent. It may happen; it happens in the case of Man; but it as easily fails to happen. In organisation the Horse is nearer to Man than the Ant; but it is far otherwise as regards intellectual development.

For this reason, when following the progress of any industry, I have taken my examples first in one group, then in another far-removed group, to return afterwards to the first. There are not, and cannot be, bonds between a solitary function of the being and its place in cla.s.sification--a place which has been determined by the form of all the organs, without even taking into account their methods of activity.

Comparative anatomy has long since removed the barriers, once thought impa.s.sable, raised by human pride between Man and the other animals. Our bodies do not differ from theirs; and moreover, such glimpses as we are able to obtain allow us to conclude that their psychic faculties are of the same nature as our own. Man in his evolution introduces no new factor.The industries in which the talents of animals are exercised demonstrate that, under the influence of the same environment, animals have reacted in the same manner as Man, and have formed the same combinations to protect themselves from cold or heat, to defend themselves against the attacks of enemies, and to ensure sufficient provision of food during those hard seasons of the year when the earth does not yield in abundance.

It must only be added, to avoid falling into exaggeration, that Man excels in all the arts, of which only scattered rudiments are found among the other animals; and we may safeguard our pride by affirming that we need not fear comparison. If our intelligence is not essentially different from that of animals, we have the satisfaction of knowing that it is much superior to theirs.

APPENDIX.

BIBLIOGRAPHY.

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 ill.u.s.trated, and edited by Pechuel Losche, has lately appeared (Leipzig und Wien, Bibliog.

Inst.i.tute, 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 Ca.s.sell'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 fromanimal 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. Buchner's Aus dem Geistesleben der Thiere (Berlin, 1877) and Houzeau's Facultes Mentales des Animaux (Brussels, 1877) may also be mentioned, and Espinas' Societes 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 cla.s.sified 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 Moller, nephew of Dr. Fritz Muller ("Die Pilzgarten einiger sudamerikanischer Ameisen." Heft 6 of Schimper's "Botanische Mittheilungen aus den Tropen." Jena: G. Fischer, 1893. Herr Moller'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, andtravelled 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 ma.s.s 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 ma.s.s, full of chambers, like a coa.r.s.e sponge, in which the ants may be seen running about, and in which, here and there, occur eggs, larvae, and pupae. This is the fungus garden. It is separated from the roof and lateral walls of the nest by a clear s.p.a.ce. 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 hyphae, which hold the particles together.

These hyphae 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 hyphae, and are termed by Moller the "Kohl-rabi clumps." The hyphae swell out at the ends into large spherical thickenings, filled with richly vacuolated protoplasm like the ordinary hyphae. These clumps of "Kohl-rabi" are only found on the surface of the garden, and form the princ.i.p.al 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 larvae. 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 gla.s.s 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, crus.h.i.+ng 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 hyphae 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 anutrient 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 ill.u.s.trated by beautiful plates and photographs of the mushroom gardens, const.i.tutes, 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.