Chapter XII. The Halicti: a Parasite
Sweat Bee (Halictus farinosus)
Do you know the Halicti? Perhaps not. There is no great harm done: it is quite possible to enjoy the few sweets of existence without knowing the Halicti. Nevertheless, when questioned persistently, these humble creatures with no history can tell us some very singular things; and their acquaintance is not to be disdained if we would enlarge our ideas upon the bewildering swarm of this world. Since we have nothing better to do, let us look into the Halicti. They are worth the trouble.
How shall we recognize them? They are manufacturers of honey, generally longer and slighter than the Bee of our hives. They constitute a numerous group that varies greatly in size and colouring. Some there are that exceed the dimensions of the Common Wasp; others might be compared with the House-fly, or are even smaller. In the midst of this variety, which is the despair of the novice, one characteristic remains invariable. Every Halictus carries the clearly-written certificate of her guild.
Examine the last ring, at the tip of the abdomen, on the dorsal surface. If your capture be an Halictus, there will be here a smooth and shiny line, a narrow groove along which the sting slides up and down when the insect is on the defensive. This slide for the unsheathed weapon denotes some member of the Halictus tribe, without distinction of size or colour. No elsewhere, in the sting-bearing order, is this original sort of groove in use. It is the distinctive mark, the emblem of the family.
Three Halicti will appear before you in this biographical fragment. Two of them are my neighbours, my familiars, who rarely fail to settle each year in the best parts of the enclosure. They occupied the ground before I did; and I should not dream of evicting them, persuaded as I am that they will well repay my indulgence. Their proximity, which allows me to visit them daily at my leisure, is a piece of good luck. Let us profit by it.
At the head of my three subjects is the Zebra Halictus (H. zebrus, WALCK.), which is beautifully belted around her long abdomen with alternate black and pale-russet scarves. Her slender shape, her size, which equals that of the Common Wasp, her simple and pretty dress, combine to make her the chief representative of the genus here.
She establishes her galleries in firm soil, where there is no danger of landslips which would interfere with the work at nesting-time. In my garden, the well-levelled paths, made of a mixture of tiny pebbles and red clayey earth, suits her to perfection. Every spring she takes possession of it, never alone, but in gangs whose number varies greatly, amounting sometimes to as many as a hundred. In this way she founds what may be described as small townships, each clearly marked out and distant from the other, in which the joint possession of the site in no way entails joint work.
Each has her home, an inviolable manor which none but the owner has the right to enter. A sound buffeting would soon call to order any adventuress who dared to make her way into another's dwelling. No such indiscretion is suffered among the Halicti. Let each keep to her own place and to herself and perfect peace will reign in this new-formed society, made up of neighbours and not of fellow-workers.
Operations begin in April, most unobtrusively, the only sign of the underground works being the little mounds of fresh earth. There is no animation in the building-yards. The labourers show themselves very seldom, so busy are they at the bottom of their pits. At moments, here and there, the summit of a tiny mole-hill begins to totter and tumbles down the slopes of the cone: it is a worker coming up with her armful of rubbish and shooting it outside, without showing herself in the open. Nothing more for the moment.
There is one precaution to be taken: the villages must be protected against the passers-by, who might inadvertently trample them under foot. I surround each of them with a palisade of reed-stumps. In the centre I plant a danger-signal, a post with a paper flag. The sections of the paths thus marked are forbidden ground; none of the household will walk upon them.
May arrives, gay with flowers and sunshine. The navvies of April have turned themselves into harvesters. At every moment I see them settling, all befloured with yellow, atop of the mole-hills now turned into craters. Let us first look into the question of the house. The arrangement of the home will give us some useful information. A spade and a three-pronged fork place the insect's crypts before our eyes.
A shaft as nearly vertical as possible, straight or winding according to the exigencies of a soil rich in flinty remains, descends to a depth of between eight and twelve inches. As it is merely a passage in which the only thing necessary is that the Halictus should find an easy support in coming and going, this long entrance-hall is rough and uneven. A regular shape and a polished surface would be out of place here. These artistic refinements are reserved for the apartments of her young. All that the Halictus mother asks is that the passage should be easy to go up and down, to ascend or descend in a hurry. And so she leaves it rugged. Its width is about that of a thick lead-pencil.
Arranged one by one, horizontally and at different heights, the cells occupy the basement of the house. They are oval cavities, three-quarters of an inch long, dug out of the clay mass. They end in a short bottle-neck that widens into a graceful mouth. They look like tiny vaccine-phials laid on their sides. All of them open into the passage.
The inside of these little cells has the gloss and polish of a stucco which our most experienced plasterers might envy. It is diapered with faint longitudinal, diamond-shaped marks. These are the traces of the polishing-tool that has given the last finish to the work. What can this polisher be? None other than the tongue, that is obvious. The Halictus has made a trowel of her tongue and licked the wall daintily and methodically in order to polish it.
This final glazing, so exquisite in its perfection, is preceded by a trimming-process. In the cells that are not yet stocked with provisions, the walls are dotted with tiny dents like those in a thimble. Here we recognize the work of the mandibles, which squeeze the clay with their tips, compress it and purge it of any grains of sand. The result is a milled surface whereon the polished layer will find a solid adhesive base. This layer is obtained with a fine clay, very carefully selected by the insect, purified, softened and then applied atom by atom, after which the trowel of the tongue steps in, diapering and polishing, while saliva, disgorged as needed, gives pliancy to the paste and finally dries into a waterproof varnish.
The humidity of the subsoil, at the time of the spring showers, would reduce the little earthen alcove to a sort of pap. The coating of saliva is an excellent preservative against this danger. It is so delicate that we suspect rather than see it; but its efficacy is none the less evident. I fill a cell with water. The liquid remains in it quite well, without any trace of infiltration.
The tiny pitcher looks as if it were varnished with galenite. The impermeability which the potter obtains by the brutal infusion of his mineral ingredients the Halictus achieves with the soft polisher of her tongue moistened with saliva. Thus protected, the larva will enjoy all the advantages of a dry berth, even in rain-soaked ground.
Should the wish seize us, it is easy to detach the waterproof film, at least in shreds. Take the little shapeless lump in which a cell has been excavated and put it in sufficient water to cover the bottom of it. The whole earthy mass will soon be soaked and reduced to a mud which we are able to sweep with the point of a hair-pencil. Let us have patience and do our sweeping gently; and we shall be able to separate from the main body the fragments of a sort of extremely fine satin. This transparent, colourless material is the upholstery that keeps out the wet. The Spider's web, if it formed a stuff and not a net, is the only thing that could be compared with it.
The Halictus' nurseries are, as we see, structures that take much time in the making. The insect first digs in the clayey earth a recess with an oval curve to it. It has its mandibles for a pick-axe and its tarsi, armed with tiny claws, for rakes. Rough though it be, this early work presents difficulties, for the Bee has to do her excavating in a narrow gully, where there is only just room for her to pass.
The rubbish soon becomes cumbersome. The insect collects it and then, moving backwards, with its fore-legs closed over the load, it hoists it up through the shaft and flings it outside, upon the mole-hill, which rises by so much above the threshold of the burrow. Next come the dainty finishing-touches: the milling of the wall, the application of a glaze of better-quality clay, the assiduous polishing with the long-suffering tongue, the waterproof coating and the jarlike mouth, a masterpiece of pottery in which the stopping-plug will be fixed when the time comes for locking the door of the room. And all this has to be done with mathematical precision.
No, because of this perfection, the grubs' chambers could never be work done casually from day to day, as the ripe eggs descend from the ovaries. They are prepared long beforehand, during the bad weather, at the end of March and in April, when flowers are scarce and the temperature subject to sudden changes. This thankless period, often cold, liable to hail-storms, is spent in making ready the home. Alone at the bottom of her shaft, which she rarely leaves, the mother works at her children's apartments, lavishing upon them those finishing-touches which leisure allows. They are completed, or very nearly, when May comes with the radiant sunshine and wealth of flowers.
We see the evidence of these long preparations in the burrows themselves, if we inspect them before the provisions are brought. All of them show us cells, about a dozen in number, quite finished, but still empty. To begin by getting all the huts built is a sensible precaution: the mother will not have to turn aside from the delicate task of harvesting and egg-laying in order to perform rough navvy's work.
Everything is ready by May. The air is balmy; the smiling lawns are gay with a thousand little flowers, dandelions, rock-roses, tansies and daisies, among which the harvesting Bee rolls gleefully, covering herself with pollen. With her crop full of honey and the brushes of her legs befloured, the Halictus returns to her village. Flying very low, almost level with the ground, she hesitates, with sudden turns and bewildered movements. It seems that the weak-sighted insect finds its way with difficulty among the cottages of its little township.
Which is its mole-hill among the many others near, all similar in appearance? It cannot tell exactly save by the sign-board of certain details known to itself alone. Therefore, still on the wing, tacking from side to side, it examines the locality. The home is found at last: the Halictus alights on the threshold of her abode and dives into it quickly.
What happens at the bottom of the pit must be the same thing that happens in the case of the other Wild Bees. The harvester enters a cell backwards; she first brushes herself and drops her load of pollen; then, turning round, she disgorges the honey in her crop upon the floury mass. This done, the unwearied one leaves the burrow and flies away, back to the flowers. After many journeys, the stack of provisions in the cell is sufficient. This is the moment to bake the cake.
The mother kneads her flour, mingles it sparingly with honey. The mixture is made into a round loaf, the size of a pea. Unlike our own loaves, this one has the crust inside and the crumb outside. The middle part of the roll, the ration which will be consumed last, when the grub has acquired some strength, consists of almost nothing but dry pollen. The Bee keeps the dainties in her crop for the outside of the loaf, whence the feeble grub-worm is to take its first mouthfuls. Here it is all soft crumb, a delicious sandwich with plenty of honey. The little breakfast-roll is arranged in rings regulated according to the age of the nurseling: first the syrupy outside and at the very end the dry inside. Thus it is ordained by the economics of the Halictus.
An egg bent like a bow is laid upon the sphere. According to the generally-accepted rule, it now only remains to close the cabin. Honey-gatherers — Anthophorae, Osmiae, Mason-bees and many others — usually first collect a sufficient stock of food and then, having laid the egg, shut up the cell, to which they need pay no more attention. The Halicti employ a different method. The compartments, each with its round loaf and its egg — the tenant and his provisions — are not closed up. As they all open into the common passage of the burrow, the mother is able, without leaving her other occupations, to inspect them daily and enquire tenderly into the progress of her family. I imagine, without possessing any certain proof, that from time to time she distributes additional provisions to the grubs, for the original loaf appears to me a very frugal ration compared with that served by the other Bees.
Certain hunting Hymenoptera, the Bembex-wasps, for instance, are accustomed to furnish the provisions in instalments: so that the grub may have fresh though dead game, they fill the platter each day. The Halictus mother has not these domestic necessities, as her provisions keep more easily; but still she might well distribute a second portion of flour to the larvae, when their appetite attains its height. I can see nothing else to explain the open doors of the cells during the feeding-period.
At last the grubs, close-watched and fed to repletion, have achieved the requisite degree of fatness; they are on the eve of being transformed into pupae. Then and not till then the cells are closed: a big clay stopper is built by the mother into the spreading mouth of the jug. Henceforth the maternal cares are over. The rest will come of itself.
Hitherto we have witnessed only the peaceful details of the housekeeping. Let us go back a little and we shall be witnesses of rampant brigandage. In May, I visit my most populous village daily, at about ten o'clock in the morning, when the victualling-operations are in full swing. Seated on a low chair in the sun, with my back bent and my arms upon my knees, I watch, without moving, until dinner-time. What attracts me is a parasite, a trumpery Gnat, the bold despoiler of the Halictus.
Has the jade a name? I trust so, without, however, caring to waste my time in enquiries that can have no interest for the reader. Facts clearly stated are preferable to the dry minutiae of nomenclature. Let me content myself with giving a brief description of the culprit. She is a Dipteron, or Fly, five millimetres long (1). Eyes, dark-red; face, white. Corselet, pearl-grey, with five rows of fine black dots, which are the roots of stiff bristles pointing backwards. Greyish belly, pale below. Black legs.
She abounds in the colony under observation. Crouching in the sun, near a burrow, she waits. As soon as the Halictus arrives from her harvesting, her legs yellow with pollen, the Gnat darts forth and pursues her, keeping behind her in all the turns of her oscillating flight. At last, the Bee suddenly dives indoors. No less suddenly the other settles on the mole-hill, quite close to the entrance. Motionless, with her head turned towards the door of the house, she waits for the Bee to finish her business. The latter reappears at last and, for a few seconds, stands on the threshold, with her head and thorax outside the hole. The Gnat, on her side, does not stir.
Often, they are face to face, separated by a space no wider than a finger's breadth. Neither of them shows the least excitement. The Halictus — judging, at least, by her tranquillity — takes no notice of the parasite lying in wait for her; the parasite, on the other hand, displays no fear of being punished for her audacity. She remains imperturbable, she, the dwarf, in the presence of the colossus who could crush her with one blow.
In vain I watch anxiously for some sign of apprehension on either side: nothing in the Halictus points to a knowledge of the danger run by her family; nor does the Gnat betray any dread of swift retribution. Plunderer and plundered stare at each other for a moment; and that is all.
If she liked, the amiable giantess could rip up with her claw the tiny bandit who ruins her home; she could crunch her with her mandibles, run her through with her stiletto. She does nothing of the sort, but leaves the robber in peace, to sit quite close, motionless, with her red eyes fixed on the threshold of the house. Why this fatuous clemency?
The Bee flies off. Forthwith, the Gnat walks in, with no more ceremony than if she were entering her own place. She now chooses among the victualled cells at her ease, for they are all open, as I have said; she leisurely deposits her eggs. No one will disturb her until the Bee's return. To flour one's legs with pollen, to distend one's crop with syrup is a task that takes long a-doing; and the intruder, therefore, has time and to spare wherein to commit her felony. Moreover, her chronometer is well-regulated and gives the exact measure of the Bee's length of absence. When the Halictus comes back from the fields, the Gnat has decamped. In some favourable spot, not far from the burrow, she awaits the opportunity for a fresh misdeed.
What would happen if a parasite were surprised at her work by the Bee? Nothing serious. I see them, greatly daring, follow the Halictus right into the cave and remain there for some time while the mixture of pollen and honey is being prepared. Unable to make use of the paste so long as the harvester is kneading it, they go back to the open air and wait on the threshold for the Bee to come out. They return to the sunlight, calmly, with unhurried steps: a clear proof that nothing untoward has occurred in the depths where the Halictus works.
A tap on the Gnat's neck, if she become too enterprising in the neighbourhood of the cake: that is all that the lady of the house seems to allow herself, to drive away the intruder. There is no serious affray between the robber and the robbed. This is apparent from the self-possessed manner and undamaged condition of the dwarf who returns from visiting the giantess engaged down in the burrow.
The Bee, when she comes home, whether laden with provisions or not, hesitates, as I have said, for a while; in a series of rapid zigzags, she moves backwards, forwards and from side to side, at a short distance from the ground. This intricate flight at first suggests the idea that she is trying to lead her persecutress astray by means of an inextricable tangle of marches and countermarches. That would certainly be a prudent move on the Bee's part; but so much wisdom appears to be denied her.
It is not the enemy that is disturbing her, but rather the difficulty of finding her own house amid the confusion of the mole-hills, encroaching one upon the other, and all the alleys of the little township, which, owing to landslips of fresh rubbish, alter in appearance from one day to the next. Her hesitation is manifest, for she often blunders and alights at the entrance to a burrow that is not hers. The mistake is at once perceived from the slight indications of the doorway.
The search is resumed with the same see-sawing flights, mingled with sudden excursions to a distance. At last, the burrow is recognized. The Halictus dives into it with a rush; but, however prompt her disappearance underground, the Gnat is there, perched on the threshold with her eyes turned to the entrance, waiting for the Bee to come out, so that she may visit the honey-jars in her turn.
When the owner of the house ascends, the other draws back a little, just enough to leave a free passage and no more. Why should she put herself out? the meeting is so peaceful that, short of further information, one would not suspect that a destroyer and destroyed were face to face. Far from being intimidated by the sudden arrival of the Halictus, the Gnat pays hardly any attention; and, in the same way, the Halictus takes no notice of her persecutress, unless the bandit pursue her and worry her on the wing. Then, with a sudden bend, the Bee makes off.
Even so do Philanthus apivorus (2) and the other game-hunters behave when the Tachina is at their heels seeking the chance to lay her egg on the morsel about to be stored away. Without jostling the parasite which they find hanging around the burrow, they go indoors quite peaceably; but, on the wing, perceiving her after them, they dart off wildly. The Tachina, however, dares not go down to the cells where the huntress stacks her provisions; she prudently waits at the door for the Philanthus to arrive. The crime, the laying of the egg, is committed at the very moment when the victim is about to vanish underground.
The troubles of the parasite of the Halictus are of quite another kind. The homing Bee has her honey in her crop and her pollen on her leg-brushes: the first is inaccessible to the thief; the second is powdery and would give no resting-place to the egg. Besides, there is not enough of it yet: to collect the wherewithal for that round loaf of hers, the Bee will have to make repeated journeys. When the necessary amount is obtained, she will knead it with the tip of her mandibles and shape it with her feet into a little ball. The Gnat's egg, were it present among the materials, would certainly be in danger during this manipulation.
The alien egg, therefore, must be laid on the finished bread; and, as the preparation takes place underground, the parasite is needs obliged to go down to the Halictus. With inconceivable daring, she does go down, even when the Bee is there. Whether through cowardice or silly indulgence, the dispossessed insect lets the other have its way.
The object of the Gnat, with her tenacious lying-in-wait and her reckless burglaries, is not to feed herself at the harvester's expense: she could get her living out of the flowers with much less trouble than her thieving trade involves. The most, I think, that she can allow herself to do in the Halictus' cellars is to take one morsel just to ascertain the quality of the victuals. Her great, her sole business is to settle her family. The stolen goods are not for herself, but for her offspring.
Let us dig up the pollen-loaves. We shall find them most often crumbled with no regard to economy, simply frittered away. We shall see two or three maggots, with pointed mouths, moving in the yellow flour scattered over the floor of the cell. These are the Gnat's progeny. With them we sometimes find the lawful owner, the grub-worm of the Halictus, but stunted and emaciated with fasting. His gluttonous companions, without otherwise molesting him, deprive him of the best of everything. The wretched starveling dwindles, shrivels up and soon disappears from view. His corpse, a mere atom, blended with the remaining provisions, supplies the maggots with one mouthful the more.
And what does the Halictus mother do in this disaster? She is free to visit her grubs at any moment; she has but to put her head into the passage of the house: she cannot fail to be apprised of their distress. The squandered loaf, the swarming mass of vermin tell their own tale. Why does she not take the intruders by the skin of the abdomen? To grind them to powder with her mandibles, to fling them out of doors were the business of a second. And the foolish creature never thinks of it, leaves the ravagers in peace!
She does worse. When the time of the nymphosis comes, the Halictus mother goes to the cells rifled by the parasite and closes them with an earthen plug as carefully as she does the rest. This final barricade, an excellent precaution when the cot is occupied by an Halictus in course of metamorphosis, becomes the height of absurdity when the Gnat has passed that way. Instinct does not hesitate in the face of this ineptitude: it seals up emptiness. I say, emptiness, because the crafty maggot hastens to decamp the instant that the victuals are consumed, as though it foresaw an insuperable obstacle for the coming Fly: it quits the cell before the Bee closes it.
To rascally guile the parasite adds prudence. All, until there is none of them left, abandon the clay homes which would be their undoing once the entrance was plugged up. The earthen niche, so grateful to the tender skin, thanks to its polished coating, so free from humidity, thanks to its waterproof glaze, ought, one would think, to make an excellent waiting-place. The maggots will have none of it. Lest they should find themselves walled in when they become frail Gnats, they go away and disperse in the neighbourhood of the ascending shaft.
My digging operations, in fact, always reveal the pupae outside the cells, never inside. I find them enshrined, one by one, in the body of the clayey earth, in a narrow recess which the emigrant worm has contrived to make for itself. Next spring, when the hour comes for leaving, the adult insect has but to creep through the rubbish, which is easy work.
Another and no less imperative reason compels this change of abode on the parasite's part. In July, a second generation of the Halictus is procreated. The Gnat, reduced on her side to a single brood, remains in the pupa state and awaits the spring of the following year before effecting her transformation. The honey-gather resumes her work in her native village; she avails herself of the pits and cells constructed in the spring, saving no little time thereby. The whole elaborate structure has remained in good condition. It needs but a few repairs to make the old house habitable.
Now what would happen if the Bee, so scrupulous in matters of cleanliness, were to find a pupa in the cell which she is sweeping? She would treat the cumbersome object as she would a piece of old plaster. It would be no more to her than any other refuse, a bit of gravel, which, seized with the mandibles, crushed perhaps, would be sent to join the rubbish-heap outside. Once removed from the soil and exposed to the inclemencies of the weather, the pupa would inevitably perish.
I admire this intelligent foresight of the maggot, which forgoes the comfort of the moment for the security of the future. Two dangers threaten it: to be immured in a casket whence the Fly can never issue; or else to die out of doors, in the unkindly air, when the Bee sweeps out the restored cells. To avoid this twofold peril, it decamps before the door is closed, before the July Halictus sets her house in order.
Let us now see what comes of the parasite's intrusion. In the course of June, when peace is established in the Halictus' home, I dig up my largest village, comprising some fifty burrows in all. None of the sorrows of this underworld shall escape me. There are four of us engaged in sifting the excavated earth through our fingers. What one has examined another takes up and examines; and then another and another yet. The returns are heartrending. We do not succeed in finding one single nymph of the Halictus. The whole of the populous city has perished; and its place has been taken by the Gnat. There is a glut of that individual's pupae. I collect them in order to trace their evolution.
The year runs its course; and the little russet kegs, into which the original maggots have hardened and contracted, remain stationary. They are seeds endowed with latent life. The heats of July do not rouse them from their torpor. In that month, the period of the second generation of the Halictus, there is a sort of truce of God: the parasite rests and the Bee works in peace. If hostilities were to be resumed straight away, as murderous in summer as they were in spring, the progeny of the Halictus, too cruelly smitten, might possibly disappear altogether. This lull readjusts the balance.
In April, when the Zebra Halictus, in search of a good place for her burrows, roams up and down the garden paths with her oscillating flight, the parasite, on its side, hastens to hatch. Oh, the precise and terrible agreement between those two calendars, the calendar of the persecutor and the persecuted! At the very moment when the Bee comes out, here is the Gnat: she is ready to begin her deadly starving-process all over again.
Were this an isolated case, one's mind would not dwell upon it: an Halictus more or less in the world makes little difference in the general balance. But, alas, brigandage in all its forms is the rule in the eternal conflict of living things! From the lowest to the highest, every producer is exploited by the unproductive. Man himself, whose exceptional rank ought to raise him above such baseness, excels in this ravening lust. He says to himself that business means getting hold of other people's cash, even as the Gnat says to herself that business means getting hold of the Halictus' honey. And, to play the brigand to better purpose, he invents war, the art of killing wholesale and of doing with glory that which, when done on a smaller scale, leads to the gallows.
Shall we never behold the realization of that sublime vision which is sung on Sundays in the smallest village-church: Gloria in excelsis Deo, et in terra pax hominibus bonae voluntatis! If war affected humanity alone, perhaps the future would have peace in store for us, seeing that generous minds are working for it with might and main; but the scourge also rages among the lower animals, which in their obstinate way, will never listen to reason. Once the evil is laid down as a general condition, it perhaps becomes incurable. Life in the future, it is to be feared, will be what it is to-day, a perpetual massacre.
Tachinid Fly (Tachina Fera)
Whereupon, by a desperate effort of the imagination, one pictures to oneself a giant capable of juggling with the planets. He is irresistible strength; he is also law and justice. He knows of our battles, our butcheries, our farm-burnings, our town-burnings, our brutal triumphs; he knows our explosives, our shells, our torpedo-boats, our ironclads and all our cunning engines of destruction; he knows as well the appalling extent of the appetites among all creatures, down to the very lowest. Well, if that just and mighty one held the earth under his thumb, would he hesitate whether he ought to crush it?
He would not hesitate…He would let things take their course. He would say to himself:
‚The old belief is right; the earth is a rotten apple, gnawed by the vermin of evil. It is a first crude attempt, a step towards a kindlier destiny. Let it be: order and justice are waiting at the end.‘
1. .195 inch.
2. The Bee-hunting Wasp. Cf. „Social Life in the Insect World“: chapter 13.