GENERAL PRECAUTIONS AGAINST POSSIBLE DANGER — SEPARATION OF FEMALES WHILE BROODING — HYGIENIC MEASURES OF BEES — PRUDENCE OF BEES — FORTIFICATIONS OF BEES — PRECAUTIONS AGAINST INQUISITIVENESS — LIGHTING UP THE NESTS.

The building of comfortable dwellings is not the last stage reached by the industry of animals. There are among them some who show genuine skill in rendering them healthy and defending them against invasions from without.

General precautions against possible danger. — Some animals show, even during the construction of the nest, extreme prudence in preventing its site from being discovered. Several authors refer to the stratagem of the Magpie, who begins several nests at the same time; but only one is intended to receive the brood, and that only is completed. The aim of the others is merely to distract attention. It is around these latter that the bird shows ostentatious activity, while it works at the real nest only for a few hours during the day, in the morning and evening.

The Crane takes equally ingenious precautions in order that its constant presence at the same spot may not arouse suspicion. It never comes or goes flying, but always on foot, concealing itself along tufts of reeds. De Homeyer even reports that the female at the time of laying covers her wings and back with mud. When dried this gives the animal a red tone, which causes it to be confused with neighbouring objects; this is intentional mimicry.

The Linnet (Fig. 41) again, wrongly accused of wanting judgment, is well aware that a pile of excrement at the foot of a tree announces a nest in the branches. It is careful to suppress this revealing sign, and every day takes it away in its beak to disperse it afar.

Birds will sometimes take the trouble to remove the eggs or the nest altogether, when the latter has been discovered, in order to avoid further risks of danger. The American Sparrow Hawk has been observed to do this, and the following incident is quoted by Bendire, from MacFarlane’s Manuscript Notes on Birds Nesting in British America, concerning the Pigeon Hawk (Falco columbarius): — “On May 25, 1864, a trusty Indian in my employ found a nest placed in a thick branch of a pine tree at a height of about six feet from the ground. It was rather loosely constructed of a few dry sticks and a small quantity of coarse hay; it then contained two eggs; both parents were seen, fired at, and missed. On the 31st he revisited the nest, which still held but two eggs, and again missed the birds. Several days later he made another visit thereto, and, to his surprise, the eggs and parents had disappeared. His first impression was that some other person had taken them; but after looking carefully around he perceived both birds at a short distance, and this led him to institute a search which soon resulted in finding that the eggs must have been removed by the parent birds to the face of a muddy bank at least forty yards distant from the original nest. A few decayed leaves had been placed under them, but nothing else in the way of lining. A third egg had been added in the interim. There can hardly be any doubt of the truth of the foregoing facts.”110Separation of females while brooding. — The Hornbill of Malacca111 assures 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 pass 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.

What can be the object of this strange custom? It has been asserted 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. Assaulted 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 fÆces that when at last able to go out they fall to the ground and perish. BÜchner 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 defÆcate; the fÆces float and are soon disintegrated.

Animals are also careful about aËration. Thus, among Bees, in a hive full of very active insects the heat rises considerably and the air is vitiated. A service for aËration 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 observer as 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 assist one another; and it is an exceedingly interesting sight which is presented to the observer when this general ‘washing up’ is in progress.”112

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 partition, 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 circumstances 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 partition, and the hole was then stopped up again.

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 circumstance, 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 hairs which 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 illustrious 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 passage 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 circumstances that are not habitual.114

Precautions against inquisitiveness. — I will finally quote a fact of defence which took place under circumstances 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 glass pane. A wooden shutter concealed this pane, but passers-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 nobody.

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 balls of dry and hardened clay. Why does the bird amass 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 balls 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