here and there, cases occur in which the animal harmonizes with surrounding objects. It would even be very strange if such cases were excluded from actuality, since everything is possible. But these rare coincidences are faced, under exactly similar conditions, by inconsistencies so strongly marked and so numerous that, having frequency on their side, they ought, in all logic, to serve as the basis of the law. Here, one fact says yes; there, a thousand facts say no. To which evidence shall we lend an ear? If we only wish to bolster up a theory, it would be prudent to listen to neither. The how and why escapes us; what we dignify with the pretentious title of a law is but a way of looking at things with our mind, a very squint-eyed way, which we adopt for the requirements of our case. Our would-be laws contain but an infinitesimal shade of reality; often indeed they are but puffed out with vain imaginings. Such is the law of mimesis, which explains the Green Grasshopper by the green leaves in which this Locust settles and is silent as to the Crioceris, that coral-red Beetle who lives on the no less green leaves of the lily.
And it is not only a mistaken interpretation: it is a clumsy pitfall in which novices allow themselves to be caught. Novices, did I say? The greatest experts themselves fall into the trap. One of our masters of entomology did me the honour to visit my laboratory. I was showing my collection of parasites. One of them, clad in black and yellow, attracted his attention.
‘This,’ said he, ‘is obviously a parasite of the Wasps.’
Surprised at the statement, I interposed:
‘By what signs do you know her?’
‘Why look: it’s the exact colouring of the Wasp, a mixture of black and yellow. It is a most striking case of mimesis.’
‘Just so; nevertheless, our black-and-yellow friend is a parasite of the Chalicodoma of the Walls, who has nothing in common, either in shape or colour, with the Wasp. This is a Leucopsis, not one of whom enters the Wasps’ nest.’
‘Then mimesis…?’
‘Mimesis is an illusion which we should do well to relegate to oblivion.’
And, with the evidence, a whole series of conclusive examples, in front of him, my learned visitor admitted with a good grace that his first convictions were based on a most ludicrous foundation.
A piece of advice to beginners: you will go wrong a thousand times for once that you are right if, when anxious to obtain a premature sight of the probable habits of an insect, you take mimesis as your guide. With mimesis above all, it is wise, when the law says that a thing is black, first to enquire whether it does not happen to be white.
Let us go on to more serious subjects and enquire into parasitism itself, without troubling any longer about the costume of the parasite. According to etymology, a parasite is one who eats another’s bread, one who lives on the provisions of others. Entomology often alters this term from its real meaning. Thus it describes as parasites the Chrysis, the Mutilla, the Anthrax, the Leucopsis, all of whom feed their family not on the provisions amassed by others, but on the very larvae which have consumed those provisions, their actual property. When the Tachinae have succeeded in laying their eggs on the game warehoused by the Bembex, the burrower’s home is invaded by real parasites, in the strict sense of the word. Around the heap of Gad- flies, collected solely for the children of the house, new guests force their way, numerous and hungry, and without the least ceremony plunge into the thick of it. They sit down to a table that was not laid for them; they eat side by side with the lawful owner; and this in such haste that he dies of starvation, though he is respected by the teeth of the interlopers who have gorged themselves on his portion.
When the Melecta has substituted her egg for the Anthophora’s, here again we see a real parasite settling in the usurped cell. The pile of honey laboriously gathered by the mother will not even be broken in upon by the nurseling for which it was intended. Another will profit by it, with none to say him nay. Tachinae and Melectae: those are the true parasites, consumers of others’ goods.
Can we say as much of the Chrysis or the Mutilla? In no wise. The Scoliae, whose habits are known to us, are certainly not parasites. (The habits of the Scolia-wasp have been described in different essays not yet translated into English.–Translator’s Note.) No one will accuse them of stealing the food of others. Zealous workers, they seek and find under ground the fat grubs on which their family will feed. They follow the chase by virtue of the same quality as the most renowned hunters, Cerceris, Sphex or Ammophila; only, instead of removing the game to a special lair, they leave it where it is, down in the burrow. Homeless poachers, they let their venison be consumed on the spot where it is caught.
In what respect do the Mutilla, the Chrysis, the Leucopsis, the Anthrax and so many others differ, in their way of living, from the Scolia? It seems to me, in none. See for yourselves. By an artifice that varies according to the mother’s talent, their grubs, either in the germ-stage or newly-born, are brought into touch with the victim that is to feed them: an unwounded victim, for most of them are without a sting; a live victim, but steeped in the torpor of the coming transformations and thus delivered without defence to the grub that is to devour it.
With them, as with the Scoliae, meals are made on the spot on game legitimately acquired by indefatigable battues or by patient stalking in which all the rules have been observed; only, the animal hunted is defenceless and does not need to be laid low with a dagger-thrust. To seek and find for one’s larder a torpid prey incapable of resistance is, if you like, less meritorious than heroically to stab the strong- jawed Rose-chafer or Rhinoceros-beetle; but since when has the title of sportsman been denied to him who blows out the brains of a harmless Rabbit, instead of waiting without flinching for the furious charge of the Wild Boar and driving his hunting-knife into him behind his shoulder? Besides, if the actual assault is without danger, the approach is attended with a difficulty that increases the merit of these second-rate poachers. The coveted game is invisible. It is confined in the stronghold of a cell and moreover protected by the surrounding wall of a cocoon. Of what prowess must not the mother be capable to determine the exact spot at which it lies and to lay her egg on its side or at least close by? For these reasons, I boldly number the Chrysis, the Mutilla and their rivals among the hunters and reserve the ignoble title of parasites for the Tachina, the Melecta, the Crocisa, the Meloe-beetle, in short, for all those who feed on the provisions of others.
All things considered, is ignoble the right epithet to apply to parasitism? No doubt, in the human race, the idler who feeds at other people’s tables is contemptible at all points; but must the animal bear the burden of the indignation inspired by our own vices? Our parasites, our scurvy parasites, live at their neighbour’s expense: the animal never; and this changes the whole aspect of the question. I know of no instance, not one, excepting man, of parasites who consume the provisions hoarded by a worker of the same species. There may be, here and there, a few cases of larceny, of casual pillage among hoarders belonging to the same trade: that I am quite ready to admit, but it does not affect things. What would be really serious and what I formally deny is that, in the same zoological species, there should be some who possessed the attribute of living at the expense of the rest. In vain do I consult my memory and my notes: my long entomological career does not furnish me with a solitary example of such a misdeed as that of an insect leading the life of a parasite upon its fellows.
When the Chalicodoma of the Sheds works, in her thousands, at her Cyclopean edifice, each has her own home, a sacred home where not one of the tumultuous swarm, except the proprietress, dreams of taking a mouthful of honey. It is as though there were a neighbourly understanding to respect the others’ rights. Moreover, if some heedless one mistakes her cell and so much as alights on the rim of a cup that does not belong to her, forthwith the owner appears, admonishes her severely and soon calls her to order. But, if the store of honey is the estate of some deceased Bee, or of some wanderer unduly prolonging her absence, then–and then alone–a kinswoman seizes upon it. The goods were waste property, which she turns to account; and it is a very proper economy. The other Bees and Wasps behave likewise: never, I say never, do we find among them an idler assiduously planning the conquest of her neighbour’s possessions. No insect is a parasite on its own species.
What then is parasitism, if one must look for it among animals of different races? Life in general is but a vast brigandage. Nature devours herself; matter is kept alive by passing from one stomach into another. At the banquet of life, each is in turn the guest and the dish; the eater of to-day becomes the eaten of tomorrow; hodie tibi, cras mihi. Everything lives on that which lives or has lived; everything is parasitism. Man is the great parasite, the unbridled thief of all that is fit to eat. He steals the milk from the Lamb, he steals the honey from the children of the Bee, even as the Melecta pilfers the pottage of the Anthophora’s sons. The two cases are similar. Is it the vice of indolence? No, it is the fierce law which for the life of the one exacts the death of the other.
In this implacable struggle of devourers and devoured, of pillagers and pillaged, of robbers and robbed, the Melecta deserves no more than we the title of ignoble; in ruining the Anthophora, she is but imitating man in one detail, man who is the infinite source of destruction. Her parasitism is no blacker than ours: she has to feed her offspring; and, possessing no harvesting-tools, ignorant besides of the art of harvesting, she uses the provisions of others who are better endowed with implements and talents. In the fierce riot of empty bellies, she does what she can with the gifts at her disposal.
CHAPTER 9. THE THEORY OF PARASITISM.
The Melecta does what she can with the gifts at her disposal. I should leave it at that, if I had not to take into consideration a grave charge brought against her. She is accused of having lost, for want of use and through laziness, the workman’s tools with which, so we are told, she was originally endowed. Finding it to her advantage to do nothing, bringing up her family free of expense, to the detriment of others, she is alleged to have gradually inspired her race with an abhorrence for work. The harvesting-tools, less and less often employed, dwindled and perished as organs having no function; the species changed into a different one; and finally idleness turned the honest worker of the outset into a parasite. This brings us to a very simple and seductive theory of parasitism, worthy to be discussed with all respect. Let us set it forth.
Some mother, nearing the end of her labours and in a hurry to lay her eggs, found, let us suppose, some convenient cells provisioned by her fellows. There was no time for nest-building and foraging; if she would save her family, she must perforce appropriate the fruit of another’s toil. Thus relieved of the tedium and fatigue of work, freed of every care but that of laying eggs, she left a progeny which duly inherited the maternal slothfulness and handed this down in its turn, in a more and more accentuated form, as generation followed on generation; for the struggle for life made this expeditious way of establishing yourself one of the most favourable conditions for the success of the offspring. At the same time, the organs of work, left unemployed, became atrophied and disappeared, while certain details of shape and colouring were modified more or less, so as to adapt themselves to the new circumstances. Thus the parasitic race was definitely established.
This race, however, was not too greatly transformed for us to be able, in certain cases, to trace its origin. The parasite has retained more than one feature of those industrious ancestors. So, for instance, the Psithyrus is extremely like the Bumble-bee, whose parasite and descendant she is. The Stelis preserves the ancestral characteristics of the Anthidium; the Coelioxys-bee recalls the Leaf-cutter.
Thus speak the evolutionists, with a wealth of evidence derived not only from correspondence in general appearance, but also from similarity in the most minute particulars. Nothing is small: I am as much convinced of that as any man; and I admire the extraordinary precision of the details furnished as a basis for the theory. But am I convinced? Rightly or wrongly, my turn of mind does not hold minutiae of structure in great favour: a joint of the palpi leaves me rather cold; a tuft of bristles does not appear to me an unanswerable argument. I prefer to question the creature direct and to let it describe its passions, its mode of life, its aptitudes. Having heard its evidence, we shall see what becomes of the theory of parasitism.
Before calling upon it to speak, why should I not say what I have on my mind? And mark me, first of all, I do not like that laziness which is said to favour the animal’s prosperity. I have also believed and I still persist in believing that activity alone strengthens the present and ensures the future both of animals and men. To act is to live; to work is to go forward. The energy of a race is measured by the aggregate of its action.
No, I do not like it at all, this idleness so much commended of science. We have quite enough of these zoological brutalities: man, the son of the Ape; duty, a foolish prejudice; conscience, a lure for the simple; genius, neurosis; patriotism, jingo heroics; the soul, a product of protoplasmic energies; God, a puerile myth. Let us raise the war-whoop and go out for scalps; we are here only to devour one another; the summum bonum is the Chicago packer’s dollar-chest! Enough, quite enough of that, without having transformism next to break down the sacred law of work. I will not hold it responsible for our moral ruin; it has not a sturdy enough shoulder to effect such a breach; but still it has done its worst.
No, once more, I do not like those brutalities which, denying all that gives some dignity to our wretched life, stifle our horizon under an extinguisher of matter. Oh, don’t come and forbid me to think, though it were but a dream, of a responsible human personality, of conscience, of duty, of the dignity of labour! Everything is linked together: if the animal is better off, as regards both itself and its race, for doing nothing and exploiting others, why should man, its descendant, show greater scruples? The principle that idleness is the mother of prosperity would carry us far indeed. I have said enough on my own account; I will call upon the animals themselves, more eloquent than I.
Are we so very sure that parasitic habits come from a love of inaction? Did the parasite become what he is because he found it excellent to do nothing? Is repose so great an advantage to him that he abjured his ancient customs in order to obtain it? Well, since I have been studying the Bee who endows her family with the property of others, I have not yet seen anything in her that points to slothfulness. On the contrary, the parasite leads a laborious life, harder than that of the worker. Watch her on a slope blistered by the sun. How busy she is, how anxious! How briskly she covers every inch of the radiant expanse, how indefatigable she is in her endless quests; in her visits, which are generally fruitless! Before coming upon a nest that suits her, she has dived a hundred times into cavities of no value, into galleries not yet victualled. And then, however kindly her host, the parasite is not always well received in the hostelry. No, it is not all roses in her trade. The expenditure of time and labour which she finds necessary in order to house an egg may easily equal or even exceed that of the worker in building her cell and filling it with honey. That industrious one has regular and continuous work, an excellent condition for success in her egg-laying; the other has a thankless and precarious task, at the mercy of a thousand accidents which endanger the great undertaking of installing the eggs. One has only to watch the prolonged hesitation of a Coelioxys seeking for the Leaf-cutters’ cells to recognize that the usurpation of another’s nest is not effected without serious difficulties. If she turned parasite in order to make the rearing of her offspring easier and more prosperous, certainly she was very ill- inspired. Instead of rest, hard work; instead of a flourishing family, a meagre progeny.
To generalities, which are necessarily vague, we will add some precise facts. A certain Stelis (Stelis nasuta, LATR.) is a parasite of the Mason-bee of the Walls. When the Chalicodoma has finished building her dome of cells upon her pebble, the parasite appears, makes a long inspection of the outside of the home and proposes, puny as she is, to introduce her eggs into this cement fortress. Everything is most carefully closed: a layer of rough plaster, at least two-fifths of an inch thick, entirely covers the central accumulation of cells, which are each of them sealed with a thick mortar plug. And it is the honey of these well-guarded chambers that has to be reached by piercing a wall almost as hard as rock.
The parasite pluckily sets to; the idler becomes a glutton for work. Atom by atom, she perforates the general enclosure and scoops out a shaft just sufficient for her passage; she reaches the lid of the cell and gnaws it until the coveted provisions appear in sight. It is a slow and painful process, in which the feeble Stelis wears herself out, for the mortar is much the same as Roman cement in hardness. I myself find a difficulty in breaking it with the point of my knife. What patient effort, then, the task requires from the parasite, with her tiny pincers!
I do not know exactly how long the Stelis takes to make her entrance- shaft, as I have never had the opportunity or rather the patience to follow the work from start to finish; but what I do know is that a Chalicodoma of the Walls, incomparably larger and stronger than the parasite, when demolishing before my eyes the lid of a cell sealed only the day before, was unable to complete her undertaking in one afternoon. I had to come to her assistance in order to discover, before the end of the day, the object of her housebreaking. When the Mason-bee’s mortar has once set, its resistance is that of stone. Now the Stelis has not only to pierce the lid of the honey-store; she must also pierce the general casing of the nest. What a time it must take her to get through such a task, a gigantic one for her poor tools!
It is done at last, after infinite labour. The honey appears. The Stelis slips through and, on the surface of the provisions, side by side with the Chalicodoma’s eggs, the number varying from time to time. The victuals will be the common property of all the new arrivals, whether the son of the house or strangers.
The violated dwelling cannot remain as it is, exposed to marauders from without; the parasite must herself wall up the breach which she has contrived. The quondam housebreaker becomes a builder. At the foot of the pebble, the Stelis collects a little of that red earth which characterizes our stony plateaus grown with lavender and thyme; she makes it into mortar by wetting it with saliva; and with the pellets thus prepared she fills up the entrance-shaft, displaying all the care and art of a regular master-mason. Only, the work clashes in colour with the Chalicodoma’s. The Bee goes and gathers her cementing-powder on the adjoining high-road, the metal of which consists of broken flint-stones, and very seldom uses the red earth under the pebble supporting the nest. This choice is apparently dictated by the fact that the chemical properties of the former are more likely to produce a solid structure. The lime of the road, mixed with saliva, yields a harder cement than red clay would do. At any rate, the Chalicodoma’s nest is more or less white because of the source of its materials. When a red speck, a few millimetres wide, appears on this pale background, it is a sure sign that a Stelis has been that way. Open the cell that lies under the red stain: we shall find the parasite’s numerous family established there. The rusty spot is an infallible indication that the dwelling has been violated: at least, it is so in my neighbourhood, where the soil is as I have described.
We see the Stelis, therefore, at first a rabid miner, using her mandibles against the rock; next a kneader of clay and a plasterer restoring broken ceilings. Her trade does not seem one of the least arduous. Now what did she do before she took to parasitism? Judging from her appearance, the transformists tell us that she was an Anthidium, that is to say, she used to gather the soft cotton-wool from the dry stalks of the lanate plants and fashion it into wallets, in which to heap up the pollen-dust which she gleaned from the flowers by means of a brush carried on her abdomen. Or else, springing from a genus akin to the cotton-workers, she used to build resin partitions in the spiral stairway of a dead Snail. Such was the trade driven by her ancestors.
Really! So, to avoid slow and painful work, to achieve an easy life, to give herself the leisure favourable to the settlement of her family, the erstwhile cotton-presser or collector of resin-drops took to gnawing hardened cement! She who once sipped the nectar of flowers made up her mind to chew concrete! Why, the poor wretch toils at her filing like a galley-slave! She spends more time in ripping up a cell than it would take her to make a cotton wallet and fill it with food. If she really meant to progress, to do better in her own interest and that of her family, by abandoning the delicate occupations of the old days, we must confess that she has made a strange mistake. The mistake would be no greater if fingers accustomed to fancy-weaving were to lay aside velvet and silk and proceed to handle the quarryman’s blocks or to break stones on the roadside.
No, the animal does not commit the folly of voluntarily embittering its lot; it does not, in obedience to the promptings of idleness, give up one condition to embrace another and a more irksome; should it blunder for once, it will not inspire its posterity with a wish to persevere in a costly delusion. No, the Stelis never abandoned the delicate art of cotton-weaving to break down walls and to grind cement, a class of work far too unattractive to efface the memory of the joys of harvesting amid the flowers. Indolence has not evolved her from an Anthidium. She has always been what she is to-day: a patient artificer in her own line, a steady worker at the task that has fallen to her share.
That hurried mother who first, in remote ages, broke into the abode of her fellows to secure a home for her eggs found this unscrupulous method, so you tell us, very favourable to the success of her race, by virtue of its economy of time and trouble. The impression left by this new policy was so profound that heredity bequeathed it to posterity, in ever-increasing proportions, until at last parasitic habits became definitely fixed. The Chalicodoma of the Sheds, followed by the Three- horned Osmia, will teach us what to think of this conjecture.
I have described in an earlier chapter my installation of Chalicodoma- hives against the walls of a porch facing the south. Here, on a level with my head, placed so that they can easily be observed, hang some tiles removed from the neighbouring roofs in winter, together with their enormous nests and their occupants. Every May, for five or six years in succession, I have assiduously watched the works of my Mason- bees. From the mass of my notes on the subject I take the following experiments which bear upon the matter under discussion.
Long ago, when I used to scatter a handful of Chalicodomae some way from home, in order to study their capacity for finding their nest again, I noticed that, if they were too long absent, the laggards found their cells closed on their return. Neighbours had taken the opportunity to lay their eggs there, after finishing the building and stocking it with provisions. The abandoned property benefited another. On realizing the usurpation, the Bee returning from her long journey soon consoled herself for the mishap. She began to break the seals of some cell or other, adjoining her own; the rest let her have her way, being doubtless too busy with their present labours to seek a quarrel with the freebooter. As soon as she had destroyed the lid, the Bee, with a sort of feverish haste that burned to repay theft by theft, did a little building, did a little victualling, as though to resume the thread of her occupations, destroyed the egg in being, laid her own and closed the cell again. Here was a touch of nature that deserved careful examination.
At eleven o’clock in the morning, when the work is at its height, I mark half-a-score of Chalicodomae with different colours, to distinguish them from one another. Some are occupied with building, others are disgorging honey. I mark the corresponding cells in the same way. As soon as the marks are quite dry, I catch the ten Bees, place them singly in screws of paper and shut them all in a box until the next morning. After twenty-four hours’ captivity, the prisoners are released. During their absence, their cells have disappeared under a layer of recent structures; or, if still exposed to view, they are closed and others have made use of them.
As soon as they are free, the ten Bees, with one exception, return to their respective tiles. They do more than this, so accurate is their memory, despite the confusion resulting from a prolonged incarceration: they return to the cell which they have built, the beloved stolen cell; they minutely explore the outside of it, or at least what lies nearest to it, if the cell has disappeared under the new structures. In cases where the home is not henceforward inaccessible, it is at least occupied by a strange egg and the door is securely fastened. To this reverse of fortune the ousted ones retort with the brutal lex talionis: an egg for an egg, a cell for a cell. You’ve stolen my house; I’ll steal yours. And, without much hesitation, they proceed to force the lid of a cell that suits them. Sometimes they recover possession of their own home, if it is possible to get into it; sometimes and more frequently they seize upon some one else’s, even at a considerable distance from their original dwelling.
Patiently they gnaw the mortar lid. As the general rough-cast covering all the cells is not applied until the end of the work, all that they need do is to demolish the lid, a hard and wearisome task, but not beyond the strength of their mandibles. They therefore attack the door, the cement disk, and reduce it to dust. The criminal is allowed to carry out her nefarious designs without the slightest interference or protest from any of her neighbours, though these must necessarily include the chief party interested. The Bee is as forgetful of her cell of yesterday as she is jealous of her actual cell. To her the present is everything; the past means nothing; and the future means no more. And so the population of the tile leave the breakers of doors to do their business in peace; none hastens to the defence of a home that might well be her own. How differently things would happen if the cell were still on the stocks! But it dates back to yesterday, to the day before; and no one gives it another thought.
It’s done: the lid is demolished; access is free. For some time, the Bee stands bending over the cell, her head half-buried in it, as though in contemplation. She goes away, she returns undecidedly; at last she makes up her mind. The egg is snapped up from the surface of the honey and flung on the rubbish-heap with no more ceremony than if the Bee were ridding the house of a bit of dirt. I have witnessed this hideous crime again and yet again; I confess to having repeatedly provoked it. In housing her egg, the Mason-bee displays a brutal indifference to the fate of her neighbour’s egg.
I see some of them afterwards busy provisioning, disgorging honey and brushing pollen into the cell already completely provisioned; I see some masoning a little at the orifice, or at least laying on a few trowels of mortar. It seems as if the Bee, although the victuals and the building are just as they should be, were resuming the work at the point at which she left it twenty-four hours before. Lastly, the egg is laid and the opening closed up. Of my captives, one, less patient than the rest, rejects the slow process of eating away the cover and decides in favour of robbery with violence, on the principle that might is right. She dislodges the owner of a half-stocked cell, keeps good watch for a long time on the threshold of the home and, when she feels herself the mistress of the house, goes on with the provisioning. I follow the ousted proprietress with my eyes. I see her seize upon a closed cell by breaking into it, behaving in all respects like my imprisoned Chalicodomae.
The whole occurrence was too significant to be left without further confirmation. I repeated the experiment, therefore, almost every year, always with the same success. I can only add that, among the Bees placed by my artifices under the necessity of making up for lost time, a few are of a more easy-going temperament. I see some building anew, as if nothing out of the way had happened; others–this is a very rare course–going to settle on another tile, as though to avoid a society of thieves; and lastly a few who bring pellets of mortar and zealously finish the lid of their own cell, although it contains a strange egg. However, housebreaking is the usual thing.
One more detail not without value: it is not necessary for you to intervene and imprison Mason-bees for a time in order to witness the acts of violence which I have described. If you follow the work of the swarm assiduously, you may occasionally find a surprise awaiting you. A Mason-bee will appear and, for no reason known to you, break open a door and lay her egg in the violated cell. From what goes before, I look upon the Bee as a laggard, kept away from the workyard by an accident, or else carried to a distance by a gust of wind. On returning after an absence of some duration, she finds her place taken, her cell used by another. The victim of an usurper’s villainy, like the prisoners in my paper screws, she behaves as they do and indemnifies herself for her loss by breaking into another’s home.
Lastly, it was a matter of learning the behaviour, after their act of violence, of the Masons who have smashed in a door, brutally expelled the egg within and replaced it by one of their own laying. When the lid is repaired to look as good as new and everything restored to order, will they continue their burglarious ways and exterminate the eggs of others to make room for their own? By no means. Revenge, that pleasure of the gods and perhaps also of Bees, is satisfied after one cell has been ripped open. All anger is appeased when the egg for which so much work has been done is safely housed. Henceforth, both prisoners and stray laggards resume their ordinary labours, indifferently with the rest. They build honestly, they provision honestly, nor meditate further evil. The past is quite forgotten until a fresh disaster occurs.
To return to the parasites: a mother chanced to find herself the mistress of another’s nest. She took advantage of this to entrust her egg to it. This expeditious method, so easy for the mother and so favourable to the success of her offspring, made such an impression on her that she transmitted the maternal indolence to her posterity. Thus the worker gradually became transformed into a parasite.
Capital! The thing goes like clockwork, as long as we have only to put our ideas on paper. But let us just consult the facts, if you don’t mind; before arguing about probabilities, let us look into things as they are. Here is the Mason-bee of the Sheds teaching us something very curious. To smash the lid of a cell that does not belong to her, to throw the egg out of doors and put her own in its place is a practice which she has followed since time began. There is no need of my interference to make her commit burglary: she commits it of her own accord, when her rights are prejudiced as the result of a too-long absence. Ever since her race has been kneading cement, she has known the law of retaliation. Countless ages, such as the evolutionists require, have made her adopt forcible usurpation as an inveterate habit. Moreover, robbery is so incomparably easy for the mother. No more cement to scratch up with her mandibles on the hard ground, no more mortar to knead, no more clay walls to build, no more pollen to gather on hundreds and hundreds of journeys. All is ready, board and lodging. Never was a better opportunity for allowing one’s self a good time. There is nothing against it. The others, the workers, are imperturbable in their good-humour. Their outraged cells leave them profoundly indifferent. There are no brawls to fear, no protests. Now or never is the moment to tread the primrose path.
Besides, your progeny will be all the better for it. You can choose the warmest and wholesomest spots; you can multiply your laying- operations by devoting to them all the time that you would have to spend on irksome occupations. If the impression produced by the violent seizure of another’s property is strong enough to be handed down by heredity, how deep should be the impression of the actual moment when the Mason-bee is in the first flush of success! The precious advantage is fresh in the memory, dating from that very instant; the mother has but to continue in order to create a method of installation favourable in the highest degree to her and hers. Come, poor Bee! Throw aside your exhausting labours, follow the evolutionists’ advice and, as you have the means at your disposal, become a parasite!
But no, having effected her little revenge, the builder returns to her masonry, the gleaner to her gleaning, with unquenchable zeal. She forgets the crime committed in a moment of anger and takes good care not to hand down any tendency towards idleness to her offspring. She knows too well that activity is life, that work is the world’s great joy. What myriads of cells has she not broken open since she has been building; what magnificent opportunities, all so clear and conclusive, has she not had to emancipate herself from drudgery! Nothing could convince her: born to work, she persists in an industrious life. She might at least have produced an offshoot, a race of housebreakers, who would invade cells by demolishing doors. The Stelis does something of the kind; but who would think of proclaiming a relationship between the Chalicodoma and her? The two have nothing in common. I call for a scion of the Mason-bee of the Sheds who shall live by the art of breaking through ceilings. Until they show me one, the theorists will only make me smile when they talk to me of erstwhile workers relinquishing their trade to become parasitic sluggards.
I also call, with no less insistence, for a descendant of the Three- horned Osmia, a descendant given to demolishing party-walls. I will describe later how I managed to make a whole swarm of these Osmiae build their nests on the table in my study, in glass tubes that enabled me to see the inmost secrets of the work of the Bee. (Cf. “Bramble-bees and Others”, by J. Henri Fabre, translated by Alexander Teixeira de Mattos: chapters 1 to 7.–Translator’s Note.) For three or four weeks, each Osmia is scrupulously faithful to her tube, which is laboriously filled with a set of chambers divided by earthen partitions. Marks of different colours painted on the thorax of the workers enable me to recognize individuals in the crowd. Each crystal gallery is the exclusive property of one Osmia; no other enters it, builds in it or hoards in it. If, through heedlessness, through momentary forgetfulness of her own house in the tumult of the city, some neighbour so much as comes and looks in at the door, the owner soon puts her to flight. No such indiscretion is tolerated. Every Bee has her home and every home its Bee.
All goes well until just before the end of the work. The tubes are then closed at the orifice with a thick plug of earth; nearly the whole swarm has disappeared; there remain on the spot a score of tatterdemalions in threadbare fleeces, worn out by a month’s hard toil. These laggards have not finished their laying. There is no lack of unoccupied tubes, for I take care to remove some of those which are full and to replace them by others that have not yet been used. Very few of the Bees decide to take possession of these new homes, which differ in no particular from the earlier ones; and even then they build only a small number of cells, which are often mere attempts at partitions.
They want something different: a nest belonging to some one else. They bore through the stopper of the inhabited tubes, a work of no great difficulty, for we have here not the hard cement of the Chalicodoma, but a simple lid of dried mud. When the entrance is cleared, a cell appears, with its store of provisions and its egg, with her brutal mandibles; she rips it open and goes and flings it away. She does worse: she eats it on the spot. I had to witness this horror many times over before I could accept it as a fact. Note that the egg devoured may very well contain the criminal’s own offspring. Imperiously swayed by the needs of her present family, the Osmia puts her past family entirely out of her mind.
Having perpetrated this child-murder, the depraved creature does a little provisioning. They all experience the same necessity to go backwards in the sequence of actions in order to pick up the thread of their interrupted occupations. Her next work is to lay her egg and then she conscientiously restores the demolished lid.
The havoc can be more sweeping still. One of these laggards is not satisfied with a single cell; she needs two, three, four. To reach the most remote, the Osmia wrecks all those which come before it. The partitions are broken down, the eggs eaten or thrown away, the provisions swept outside and often even carried to a distance in great lumps. Covered with dust from the loose plaster of the demolition, floured all over with the rifled pollen, sticky with the contents of the mangled eggs, the Osmia, while at her brigand’s work, is altered beyond recognition. Once the place is cleared, everything resumes its normal course. Provisions are laboriously brought to take the place of those which have been thrown away; eggs are laid, one on each heap of food; the partitions are built up again; and the massive plug sealing the whole structure is made as good as new.
Crimes of this kind recur so often that I am obliged to interfere and place in safety the nests which I wish to keep intact. And nothing as yet explains this brigandage, bursting forth at the end of the work like a moral epidemic, like a frenzied delirium. I should say nothing if the site were lacking; but the tubes are there, close by, empty and quite fit to receive the eggs. The Osmia refuses them, she prefers to plunder. Is it from weariness, from a distaste for work after a period of fierce activity? Not at all; for, when a row of cells has been stripped of its contents, after the ravage and waste, she has to come back to ordinary work, with all its burdens. The labour is not reduced; it is increased. It would pay the Bee infinitely better, if she wants to continue her laying, to make her home in an unoccupied tube. The Osmia thinks differently. Her reasons for acting as she does escape me. Can there be ill-conditioned characters among her, characters that delight in a neighbour’s ruin? There are among men.
In the privacy of her native haunts, the Osmia, I have no doubt, behaves as in my crystal galleries. Towards the end of the building- operations, she violates others’ dwellings. By keeping to the first cell, which it is not necessary to empty in order to reach the next, she can utilize the provisions on the spot and shorten to that extent the longest part of her work. As usurpations of this kind have had ample time to become inveterate, to become inbred in the race, I ask for a descendant of the Osmia who eats her grandmother’s egg in order to establish her own egg.
This descendant I shall not be shown; but I may be told that she is in process of formation. The outrages which I have described are preparing a future parasite. The transformists dogmatize about the past and dogmatize about the future, but as seldom as possible talk to us about the present. Transformations have taken place, transformations will take place; the pity of it is that they are not actually taking place. Of the three tenses, one is lacking, the very one which directly interests us and which alone is clear of the incubus of theory. This silence about the present does not please me overmuch, scarcely more than the famous picture of “The Crossing of the Red Sea” painted for a village chapel. The artist had put upon the canvas a broad ribbon of brightest scarlet; and that was all.
‘Yes, that’s the Red Sea,’ said the priest, examining the masterpiece before paying for it. ‘That’s the Red Sea, right enough; but where are the Israelites?’
‘They have passed,’ replied the painter.
‘And the Egyptians?’
‘They are on the way.’
Transformations have passed, transformations are on the way. For mercy’s sake, cannot they show us transformations in the act? Must the facts of the past and the facts of the future necessarily exclude the facts of the present? I fail to understand.
I call for a descendant of the Chalicodoma and a descendant of the Osmia who have robbed their neighbours with gusto, when occasion offered, since the origin of their respective races, and who are working industriously to create a parasite happy in doing nothing. Have they succeeded? No. Will they succeed? Yes, people maintain. For the moment, nothing. The Osmiae and Chalicodomae of to-day are what they were when the first trowel of cement or mud was mixed. Then how many ages does it take to form a parasite? Too many, I fear, for us not to be discouraged.
If the sayings of the theorists are well-founded, going on strike and living by shifts was not always enough to assure parasitism. In certain cases, the animal must have had to change its diet, to pass from live prey to vegetarian fare, which would entirely subvert its most essential characteristics. What should we say to the Wolf giving up mutton and browsing on grass, in obedience to the dictates of idleness? The boldest would shrink from such an absurd assumption. And yet transformism leads us straight to it.
Here is an example: in July, I split some bramble-stems in which Osmia tridentata has built her nests. In the long series of cells, the lower already hold the Osmia’s cocoons, while the upper contain the larva which has nearly finished consuming its provisions and the topmost show the victuals untouched, with the Osmia’s egg upon them. It is a cylindrical egg, rounded at both extremities, of a transparent white and measuring four to five millimetres in length. (.156 to .195 inch.- -Translator’s Note.) It lies slantwise, one end of it resting on the food and the other sticking up at some distance above the honey. Now, by multiplying my visits to the fresh cells, I have on several occasions made a very valuable discovery. On the free end of the Osmia’s egg, another egg is fixed; an egg quite different in shape, white and transparent like the first, but much smaller and narrower, blunt at one end and tapering into a rather sharp point at the other. It is two millimetres long by half a millimetre wide. (.078 and .019 inch.–Translator’s Note.) It is undeniably the egg of a parasite, a parasite which compels my attention by its curious method of installing its family.
It opens before the Osmia’s egg. The tiny grub, as soon as it is born, begins to drain the rival egg, of which it occupied the top part, high up above the honey. The extermination soon becomes perceptible. You can see the Osmia’s egg turning muddy, losing its brilliancy, becoming limp and wrinkled. In twenty-four hours, it is nothing but an empty sheath, a crumpled bit of skin. All competition is now removed; the parasite is the master of the house. The young grub, when demolishing the egg, was active enough: it explored the dangerous thing which had to be got rid of quickly, it raised its head to select and multiply the attacking-points. Now, lying at full length on the surface of the honey, it no longer shifts its position; but the undulations of the digestive canal betray its greedy absorption of the Osmia’s store of food. The provisions are finished in a fortnight and the cocoon is woven. It is a fairly firm ovoid, of a very dark-brown colour, two characteristics which at once distinguish it from the Osmia’s pale, cylindrical cocoon. The hatching takes place in April or May. The puzzle is solved at last: the Osmia’s parasite is a Wasp called the Spotted Sapyga (Sapyga punctata, V.L.)
Now where are we to class this Wasp, a true parasite in the strict sense of the word, that is to say, a consumer of others’ provisions. Her general appearance and her structure make it clear to any eye more or less familiar with entomological shapes that she belongs to a species akin to that of the Scoliae. Moreover, the masters of classification, so scrupulous in their comparison of characteristics, agree in placing the Sapygae immediately after the Scoliae and a little before the Mutillae. The Scoliae feed their grubs on prey; so do the Mutillae. The Osmia’s parasite, therefore, if it really derives from a transformed ancestor, is descended from a flesh-eater, though it is now an eater of honey. The Wolf does more than become a Sheep: he turns himself into a sweet-tooth.
‘You will never get an apple-tree out of an acorn,’ Franklin tells us, with that homely common-sense of his.
In this case, the passion for jam must have sprung from a love of venison. Any theory might well be deficient in balance when it leads to such vagaries as this.
I should have to write a volume if I would go on setting forth my doubts. I have said enough for the moment. Man, the insatiable enquirer, hands down from age to age his questions about the whys and wherefores of origins. Answer follows answer, is proclaimed true to-day and recognized as false tomorrow; and the goddess Isis continues veiled.
CHAPTER 10. THE TRIBULATIONS OF THE MASON-BEE.
To illustrate the methods of those who batten on others’ goods, the plunderers who know no rest till they have wrought the destruction of the worker, it would be difficult to find a better instance than the tribulations suffered by the Chalicodoma of the Walls. The Mason who builds on the pebbles may fairly boast of being an industrious workwoman. Throughout the month of May, we see her black squads, in the full heat of the sun, digging with busy teeth in the mortar-quarry of the road hard by. So great is her zeal that she hardly moves out of the way of the passer-by; more than one allows herself to be crushed underfoot, absorbed as she is in collecting her cement.
The hardest and driest spots, which still retain the compactness imparted by the steam-roller, are the favourite veins; and the work of making the pellet is slow and painful. It is scraped up atom by atom; and, by means of saliva, turned into mortar then and there. When it is all well kneaded and there is enough to make a load, the Mason sets off with an impetuous flight, in a straight line, and makes for her pebble, a few hundred paces away. The trowel of fresh mortar is soon spent, either in adding another storey to the turret-shaped edifice, or in cementing into the wall lumps of gravel that give it greater solidity. The journeys in search of cement are renewed until the structure attains the regulation height. Without a moment’s rest, the Bee returns a hundred times to the stone-yard, always to the one spot recognized as excellent.
The victuals are now collected: honey and flower-dust. If there is a pink carpet of sainfoin anywhere in the neighbourhood, ’tis there that the Mason goes plundering by preference, though it cost her a four hundred yards’ journey every time. Her crop swells with honeyed exudations, her belly is floured with pollen. Back to the cell, which slowly fills; and back straightway to the harvest-field. And all day long, with not a sign of weariness, the same activity is maintained as long as the sun is high enough. When it is late, if the house is not yet closed, the Bee retires to her cell to spend the night there, head downwards, tip of her abdomen outside, a habit foreign to the Chalicodoma of the Sheds. Then and then alone the Mason rests; but it is a rest that is in a sense equivalent to work, for, thus placed, she blocks the entrance to the honey-store and defends her treasure against twilight or night marauders.
Being anxious to form some estimate of the total distance covered by the Bee in the construction and provisioning of a single cell, I counted the number of steps from a nest to the road where the mortar was mixed and from the same nest to the sainfoin-field where the harvest was gathered. I took such note as my patience permitted of the journeys made in both directions; and, completing these data with a comparison between the work done and that which remained to do, I arrived at nine and a half miles as the result of the total travelling. Of course, I give this figure only as a rough calculation; greater precision would have demanded more perseverance than I can boast.
Such as it is, the result, which is probably under the actual figure in many cases, is of a kind that gives us a vivid idea of the Mason- bee’s activity. The complete nest will comprise about fifteen cells. Moreover, the heap of cells will be coated at the end with a layer of cement a good finger’s-breadth thick. This massive fortification, which is less finished than the rest of the work but more expensive in materials, represents perhaps in itself one half of the complete task, so that, to establish her dome, Chalicodoma muraria, coming and going across the arid table-land, traverses altogether a distance of 275 miles, which is nearly half of the greatest dimension of France from north to south. Afterwards, when, worn out with all this fatigue, the Bee retires to a hiding-place to languish in solitude and die, she is surely entitled to say:
‘I have laboured, I have done my duty!’
Yes, certainly, the Mason has toiled with a vengeance. To ensure the future of her offspring, she has spent her own life without reserve, her long life of five or six weeks’ duration; and now she breathes her last, contented because everything is in order in the beloved house: copious rations of the first quality; a shelter against the winter frosts; ramparts against incursions of the enemy. Everything is in order, at least so she thinks; but, alas, what a mistake the poor mother is making! Here the hateful fatality stands revealed, aspera fata, which ruins the producer to provide a living for the drone; here we see the stupid and ferocious law that sacrifices the worker for the idler’s benefit. What have we done, we and the insects, to be ground with sovran indifference under the mill-stone of such wretchedness? Oh, what terrible, what heart-rending questions the Mason-bee’s misfortunes would bring to my lips, if I gave free scope to my sombre thoughts! But let us avoid these useless whys and keep within the province of the mere recorder.
There are some ten of them plotting the ruin of the peaceable and industrious Bee; and I do not know them all. Each has her own tricks, her own art of injury, her own exterminating tactics, so that no part of the Mason’s work may escape destruction. Some seize upon the victuals, others feed on the larvae, others again convert the dwelling to their own use. Everything has to submit: cell, provisions, scarce- weaned nurselings.
The stealers of food are the Stelis-wasp (Stelis nasuta) and the Dioxys-bee (Dioxys cincta). I have already said how, in the Mason’s absence, the Stelis perforates the dome of cell after cell, lays her eggs there and afterwards repairs the breach with a mortar made of red earth, which at once betrays the parasite’s presence to a watchful eye. The Stelis, who is much smaller than the Chalicodoma, finds enough food in a single cell for the rearing of several of her grubs. The mother lays a number of eggs, which I have seen vary between the extremes of two and twelve, on the surface, next to the Mason’s egg, which itself undergoes no outrage whatever.
Things do not go so badly at first. The feasters swim–it is the only word–in the midst of plenty; they eat and digest like brothers. Presently, times become hard for the hostess’ son; the food decreases, dearth sets in; and at length not an atom remains, although the Mason’s larva has attained at most a quarter of its growth. The others, more expeditious feeders, have exhausted the victuals long before the victim has finished his normal repast. The swindled grub shrivels up and dies, while the gorged larvae of the Stelis begin to spin their strong little brown cocoons, pressed close together and lumped into one mass, so as to make the best use of the scanty space in the crowded dwelling. Should you inspect the cell later, you will find, between the heaped cocoons on the wall, a little dried-up corpse. It is the larva that was such an object of care to the mother Mason. The efforts of the most laborious of lives have ended in this lamentable relic. It has happened to me just as often, when examining the secrets of the cell which is at once cradle and tomb, not to come upon the deceased grub at all. I picture the Stelis, before laying her own eggs, destroying the Chalicodoma’s egg and eating it, as the Osmiae do among themselves; or I picture the dying thing, an irksome mass for the numerous spinners at work in a narrow habitation, being cut to pieces to make room for the medley of cocoons. But to so many deeds of darkness I would not like to add another by an oversight; and I prefer to admit that I failed to perceive the grub that died of hunger.
Let us now show up the Dioxys. At the time when the work of construction is in progress, she is an impudent visitor of the nests, exploiting with the same effrontery the enormous cities of the Mason- bee of the Sheds and the solitary cupolas of the Mason-bee of the Pebbles. An innumerable population, coming and going, humming and buzzing, strikes her with no awe. On the tiles hanging from the walls of my porch I see her, with her red scarf round her body, stalking with sublime assurance over the ridged expanse of nests. Her black schemes leave the swarm profoundly indifferent; not one of the workers dreams of chasing her off, unless she should come bothering too closely. Even then, all that happens is a few signs of impatience on the part of the hustled Bee. There is no serious excitement, no eager pursuits such as the presence of a mortal enemy might lead us to suspect. They are there in their thousands, each armed with her dagger; any one of them is capable of slaying the traitress; and not one attacks her. The danger is not suspected.
Meanwhile, she inspects the workyard, moves freely among the ranks of the Masons and bides her time. If the owner be absent, I see her diving into a cell, coming out again a moment later with her mouth smeared with pollen. She has been to try the provisions. A dainty connoisseur, she goes from one store to another, taking a mouthful of honey. Is it a tithe for her personal maintenance, or a sample tested for the benefit of her coming grub? I should not like to say. What I do know is that, after a certain number of these tastings, I catch her stopping in a cell, with her abdomen at the bottom and her head at the orifice. This is the moment of laying, unless I am much mistaken.
When the parasite is gone, I inspect the home. I see nothing abnormal on the surface of the mass. The sharper eye of the owner, when she gets back, sees nothing either, for she continues the victualling without betraying the least uneasiness. A strange egg, laid on the provisions, would not escape her. I know how clean she keeps her warehouse; I know how scrupulously she casts out anything introduced by my agency: an egg that is not hers, a bit of straw, a grain of dust. So, according to my evidence and that of the Chalicodoma, which is more conclusive, the Dioxys’s egg, if it is really laid then, is not placed on the surface.
I suspect, without having yet verified my suspicion–and I reproach myself for the neglect–I suspect that the egg is buried in the heap of pollen-dust. When I see the Dioxys come out of a cell with her mouth all over yellow flour, perhaps she has been surveying the ground and preparing a hiding-place for her egg. What I take for a mere tasting might well be a more serious act. Thus concealed, the egg escapes the eagle eye of the Bee, whereas, if left uncovered, it would inevitably perish, would be flung on the rubbish heap at once by the owner of the nest. When the Spotted Sapyga lays her egg on that of the Bramble-dwelling Osmia, she does the deed under cover of darkness, in the gloom of a deep well to which not the least ray of light can penetrate; and the mother, returning with her pellet of green putty to build the closing partition, does not see the usurping germ and is ignorant of the danger. But here everything happens in broad daylight; and this demands more cunning in the method of installation.
Besides, it is the one favourable moment for the Dioxys. If she waits for the Mason-bee to lay, it is too late, for the parasite is not able to break down doors, as the Stelis does. As soon as her egg is laid, the Mason-bee of the Sheds comes out of her cell and at once turns round and proceeds to close it up with the pellet of mortar which she holds ready in her mandibles. The material is employed with such method that the actual sealing is done in a moment: the other pellets, the object of repeated journeys, will serve merely to increase the thickness of the lid. The chamber is inaccessible to the Dioxys from the first touch of the trowel. Hence it is absolutely necessary for her to see to her egg before the Mason-bee of the Sheds has disposed of hers and no less necessary to conceal it from the Mason’s watchful eye.
The difficulties are not so great in the nests of the Mason-bee of the Pebbles. After this Bee has laid her egg, she leaves it for a time to go in search of the cement needed for closing the cell; or, if she already holds a pellet in her mandibles, this is not enough to seal it properly, as the orifice is larger. More pellets are needed to wall up the entrance entirely. The Dioxys would have time to strike her blow during the mother’s absences; but everything seems to suggest that she behaves on the pebbles as she does on the tiles. She steals a march by hiding the egg in the mass of pollen and honey.
What becomes of the Mason’s egg confined in the same cell with the egg of the Dioxys? In vain have I opened nests at every season; I have never found a vestige of the egg nor of the grub of either Chalicodoma. The Dioxys, whether as a larva on the honey, or enclosed in its cocoon, or as the perfect insect, was always alone. The rival had disappeared without a trace. A suspicion thereupon suggests itself; and the facts are so compelling that the suspicion is almost equal to a certainty. The parasitic grub, which hatches earlier than the other, emerges from its hiding-place, from the midst of the honey, comes to the surface and, with its first bite, destroys the egg of the Mason-bee, as the Sapyga does the egg of the Osmia. It is an odious, but a supremely efficacious method. Nor must we cry out too loudly against such foul play on the part of a new born infant: we shall meet with even more heinous tactics later. The criminal records of life are full of these horrors which we dare not search too deeply. An infinitesimal creature, a barely-visible grub, with the swaddling- clothes of its egg still clinging to it, is led by instinct, at its first inspiration, to exterminate whatever is in its way.
So the Mason’s egg is exterminated. Was it really necessary in the Dioxys’ interest? Not in the least. The hoard of provisions is too large for its requirements in a cell of the Chalicodoma of the Sheds; how much more so in a cell of the Chalicodoma of the Pebbles! She eats not a half, hardly a third of it. The rest remains as it was, untouched. We see here, in the destruction of the Mason’s egg, a flagrant waste which aggravates the crime. Hunger excuses many things; for lack of food, the survivors on the raft of the Medusa indulged in a little cannibalism; but here there is enough food and to spare. When there is more than she needs, what earthly motive impels the Dioxys to destroy a rival in the germ stage? Why cannot she allow the larva, her mess-mate, to take advantage of the remains and afterwards to shift for itself as best it can? But no: the Mason-bee’s offspring must needs be stupidly sacrificed on the top of provisions which will only grow mouldy and useless! I should be reduced to the gloomy lucubrations of a Schopenhauer if I once let myself begin on parasitism.
Such is a brief sketch of the two parasites of the Chalicodoma of the Pebbles, true parasites, consumers of provisions hoarded on behalf of others. Their crimes are not the bitterest tribulations of the Mason- bee. If the first starves the Mason’s grub to death, if the second makes it perish in the egg, there are others who have a more pitiable ending in store for the worker’s family. When the Bee’s grub, all plump and fat and greasy, has finished its provisions and spun its cocoon wherein to sleep the slumber akin to death, the necessary period of preparation for its future life, these other enemies hasten to the nests whose fortifications are powerless against their hideously ingenious methods. Soon on the sleeper’s body lies a nascent grub which feasts in all security on the luscious fare. The traitors who attack the larvae in their lethargy are three in number: an Anthrax, a Leucopsis and a microscopic dagger-wearer. (Monodontomerus cupreus. For this and the Anthrax, cf. “The Life of the Fly”: chapters 2 and 3. The Leucopsis is a Hymenopteron, the essay upon whom forms the concluding chapter of the present volume.–Translator’s Note.) Their story deserves to be told without reticence; and I shall tell it later. For the moment, I merely mention the names of the three exterminators.
The provisions are stolen, the egg is destroyed. The young grub dies of hunger, the larva is devoured. Is that all? Not yet. The worker must be exploited thoroughly, in her work as well as in her family. Here are some now who covet her dwelling. When the Mason is constructing a new edifice on a pebble, her almost constant presence is enough to keep the aspirants to free lodgings at a distance; her strength and vigilance overawe whoso would annex her masonry. If, in her absence, one greatly daring thinks of visiting the building, the owner soon appears upon the scene and ousts her with the most discouraging animosity. She has no need then to fear the entrance of unwelcome tenants while the house is new. But the Bee of the Pebbles also uses old dwellings for her laying, as long as they are not too much dilapidated. In the early stages of the work, neighbours compete for these with an eagerness which shows the value attached to them. Face to face, at times with their mandibles interlocked, now both rising into the air, now coming down again, then touching ground and rolling over each other, next flying up again, for hours on end they will wage battle for the property at issue.
A ready-made nest, a family heirloom which needs but a little restoring, is a precious thing for the Mason, ever sparing of her time. We find so many of the old homes repaired and restocked that I suspect the Bee of laying new foundations only when there are no secondhand nests to be had. To have the chambers of a dome occupied by a stranger therefore means a serious privation.
Now several Bees, however industrious in gathering honey, building party-walls and contriving receptacles for provisions, are less clever at preparing the resorts in which the cells are to be stacked. The abandoned chambers of the Chalicodoma, now larger than they were originally, through the addition of the hall of exit, are first-rate acquisitions for them. The great thing is to occupy these chambers first, for here possession is nine parts of the law. Once established, the Mason is not disturbed in her home, while she, in her turn, does not disturb the stranger who has settled down before her in an old nest, the patrimony of her family. The disinherited one leaves the Bohemian to enjoy the ruined manor in peace and goes to another pebble to establish herself at fresh expense.
In the first rank of these free tenants, I will place an Osmia (Osmia cyanoxantha, PEREZ) and a Megachile, or Leaf-cutting Bee (Megachile apicalis, SPIN.) (Cf. “Bramble-dwellers and Others”: chapter 8.– Translator’s Note.), both of whom work in May, at the same time as the Mason, while both are small enough to lodge from five to eight cells in a single chamber of the Chalicodoma, a chamber increased by the addition of an outer hall. The Osmia subdivides this space into very irregular compartments by means of slanting, upright or curved partitions, subject to the dictates of space. There is no art, consequently, in the accumulation of little cells; the architect’s only task is to use the breadth at her disposal in a frugal manner. The material employed for the partitions is a green, vegetable putty, which the Osmia must obtain by chewing the shredded leaves of a plant whose nature is still uncertain. The same green paste serves for the thick plug that closes the abode. But in this case the insect does not use it unadulterated. To give greater power of resistance to the work, it mixes a number of bits of gravel with the vegetable cement. These materials, which are easily picked up, are lavishly employed, as though the mother feared lest she should not fortify sufficiently the entrance to her dwelling. They form a sort of coarse stucco, on the more or less smooth cupola of the Chalicodoma; and this unevenness, as well as the green colouring of its mortar of masticated leaves, at once betrays the Osmia’s nest. In course of time, under the prolonged action of the air, the vegetable putty turns brown and assumes a dead- leaf tint, especially on the outside of the plug; and it would then be difficult for any one who had not seen them when freshly made to recognize their nature.
The old nests on the pebbles seem to suit other Osmiae. My notes mention Osmia Morawitzi, PEREZ, and Osmia cyanea, KIRB., as having been recognized in these dwellings, although they are not very assiduous visitors. Lastly, to complete the enumeration of the Bees known to me as making their homes in the Mason’s cupolas, I must add Megachile apicalis, who piles in each cell a half-dozen or more honey- pots constructed with disks cut from the leaves of the wild rose, and an Anthidium whose species I cannot state, having seen nothing of her but her white cotton sacks.
The Mason-bee of the Sheds, on the other hand, supplies free lodgings to two species of Osmiae, Osmia tricornis, LATR., and Osmia Latreillii, SPIN., both of whom are quite common. The Three-horned Osmia frequents by preference the habitations of the Bees that build their nests in populous colonies, such as the Chalicodoma of the Sheds and the Hairy-footed Anthophora. Latreille’s Osmia is nearly always found with the Three-horned Osmia at the Chalicodoma’s.
The real builder of the city and the exploiter of the labour of others work together, at the same period, form a common swarm and live in perfect harmony, each Bee of the two species attending to her business in peace. They share and share alike, as though by tacit agreement. Is the Osmia discreet enough not to put upon the good-natured Mason and to utilize only abandoned passages and waste cells? Or does she take possession of the home of which the real owners could themselves have made use? I lean in favour of usurpation, for it is not rare to see the Chalicodoma of the Sheds clearing out old cells and using them as does her sister of the Pebbles. Be this as it may, all this little busy world lives without strife, some building anew, others dividing up the old dwelling.
Those Osmiae, on the contrary, who are the self-invited guests of the Mason-bee of the Pebbles are the sole occupants of the dome. The cause of this isolation lies in the unsociable temper of the proprietress. The old nest does not suit her from the moment that she sees it occupied by another. Instead of going shares, she prefers to seek elsewhere a dwelling where she can work in solitude. Her gracious surrender of a most excellent lodging in favour of a stranger who would be incapable of offering the least resistance if a dispute arose proves the great immunity enjoyed by the Osmia in the home of the worker whom she exploits. The common and peaceful swarming of the Mason-bee of the Sheds and the two cell-borrowing Osmiae proves it in a still more positive fashion. There is never a fight for the acquisition of another’s goods or the defence of one’s own property; never a brawl between Osmiae and Chalicodomae. Robber and robbed live on the most neighbourly terms. The Osmia considers herself at home; and the other does nothing to undeceive her. If the parasites, so deadly to the workers, move about in their very ranks with impunity, without arousing the faintest excitement, an equally complete indifference must be shown by the dispossessed owners to the presence of the usurpers in their old homes. I should be greatly put to it if I were asked to reconcile this calmness on the part of the expropriated one with the ruthless competition that is said to sway the world. Fashioned so as to instal herself in the Mason’s property, the Osmia meets with a peaceful reception from her. My feeble eyes can see no further.
I have named the provision-thieves, the grub-murderers and the house- grabbers who levy tribute on the Mason-bee. Does that end the list? Not at all. The old nests are cities of the dead. They contain Bees who, on achieving the perfect state, were unable to open the exit-door through the cement and who withered in their cells; they contain dead larvae, turned into black, brittle cylinders; untouched provisions, both mouldy and fresh, on which the egg has come to grief; tattered cocoons; shreds of skins; relics of the transformation.
If we remove the nest of the Chalicodoma of the Sheds from its tile–a nest sometimes quite eight inches thick–we find live inhabitants only in a thin outer layer. All the remainder, the catacombs of past generations, is but a horrible heap of dead, shrivelled, ruined, decomposed things. Into this sub-stratum of the ancient city the unreleased Bees, the untransformed larvae fall as dust; here the honey-stores of old go sour, here the uneaten provisions are reduced to mould.
Three undertakers, all members of the Beetle tribe, a Clerus, a Ptinus and an Anthrenus, batten on these remains. The larvae of the Anthrenus and the Ptinus gnaw the ashes of the corpses; the larva of the Clerus, with the black head and the rest of its body a pretty pink, appeared to me to be breaking into the old jam-pots filled with rancid honey. The perfect insect itself, garbed in vermilion with blue ornaments, is fairly common on the surface of the clay slabs during the working season, strolling leisurely through the yard to taste here and there the drops of honey oozing from some cracked pot. Notwithstanding his showy livery, so unlike the workers’ sombre frieze, the Chalicodomae leave him in peace, as though they recognized in him the scavenger whose duty it is to keep the sewers wholesome.
Ravaged by the passing years, the Mason’s home at last falls into ruin and becomes a hovel. Exposed as it is to the direct action of wind and weather, the dome built upon a pebble chips and cracks. To repair it would be too irksome, nor would that restore the original solidity of the shaky foundation. Better protected by the covering of a roof, the city of the sheds resists longer, without however escaping eventual decay. The storeys which each generation adds to those in which it was born increase the thickness and the weight of the edifice in alarming proportions. The moisture of the tile filters into the oldest layers, wrecks the foundations and threatens the nest with a speedy fall. It is time to abandon for good the house with its cracks and rents.
Thereupon the crumbling apartments, on the pebble as well as on the tile, become the home of a camp of gypsies who are not particular where they find a shelter. The shapeless hovel, reduced to a fragment of a wall, finds occupants, for the Mason’s work must be exploited to the utmost limits of possibility. In the blind alleys, all that remains of the former cells, Spiders weave a white-satin screen, behind which they lie in wait for the passing game. In nooks which they repair in summary fashion with earthen embankments or clay partitions, Hunting Wasps–Pompili and Tripoxyla–store up small members of the Spider tribe, including sometimes the Weaving Spiders who live in the same ruins.
I have said nothing yet of the Chalicodoma of the Shrubs. My silence is not due to negligence, but to the circumstance that I am almost destitute of facts relating to her parasites. Of the many nests which I have opened in order to study their inhabitants, only one so far has been invaded by strangers. This nest, the size of a large walnut, was fixed on a pomegranate-branch. It comprised eight cells, of which seven were occupied by the Chalicodoma, and the eighth by a little Chalcis, the plague of a whole host of the Bee-tribe. Apart from this instance, which was not a very serious case, I have seen nothing. In those aerial nests, swinging at the end of a twig, not a Dioxys, a Stelis, an Anthrax, a Leucopsis, those dread ravagers of the other two Masons; never any Osmiae, Megachiles or Anthidia, those lodgers in the old buildings.
The absence of the latter is easily explained. The Chalicodoma’s masonry does not last long on its frail support. The winter winds, when the shelter of the foliage has disappeared, must easily break the twig, which is little thicker than a straw and liable to give way by reason of its heavy burden. Threatened with an early fall, if it is not already on the ground, last year’s dwelling is not restored to serve the needs of the present generation. The same nest does not serve twice; and this does away with the Osmiae and with their rivals in the art of utilizing old cells.
The elucidation of this point does not remove the obscurity of the next. I can see nothing to account for the absence or at least the extreme rareness of usurpers of provisions and consumers of grubs, both of whom are very indifferent to the new or old conditions of the nest, so long as the cells are well stocked. Can it be that the lofty position of the edifice and the shaky support of the twig arouse distrust in the Dioxys and other malefactors? For lack of a better explanation, I will leave it at that.
If my idea is not an empty fancy, we must admit that the Chalicodoma of the Shrubs was singularly well-inspired in building in mid-air. You have seen of what misfortunes the other two are victims. If I take a census of the population of a tile, many a time I find the Dioxys and the Mason-bee in almost equal proportions. The parasite has wiped out half the colony. To complete the disaster, it is not unusual for the grub-eaters, the Leucopsis and her rival, the pygmy Chalcis, to have decimated the other half. I say nothing of Anthrax sinuata, whom I sometimes see coming from the nests of the Chalicodoma of the Sheds; her larva preys on the Three-horned Osmia, the Mason-bee’s visitor.
All solitary though she be on her boulder, which would seem the proper thing to keep away exploiters, the scourge of dense populations, the Chalicodoma of the Pebbles is no less sorely tried. My notes abound in cases such as the following: of the nine cells in one dome, three are occupied by the Anthrax, two by the Leucopsis, two by the Stelis, one by the Chalcis and the ninth by the Mason. It is as though the four miscreants had joined forces for the massacre: the whole of the Bee’s family has disappeared, all but one young mother saved from the disaster by her position in the centre of the citadel. I have sometimes stuffed my pockets with nests removed from their pebbles without finding a single one that has not been violated by one or other of the malefactors and oftener still by several of them at a time. It is almost an event for me to find a nest intact. After these funereal records, I am haunted by a gloomy thought: the weal of one means the woe of another.
CHAPTER 11. THE LEUCOPSES.
(This chapter should be read in conjunction with the essays entitled “The Anthrax” and “Larval Dimorphism”, forming chapters 2 and 4 of “The Life of the Fly.”–Translator’s Note.)
Let us visit the nests of Chalicodoma muraria in July, detaching them from their pebbles with a sideward blow, as I explained when telling the story of the Anthrax. The Mason-bee’s cocoons with two inhabitants, one devouring, the other in process of being devoured, are numerous enough to allow me to gather some dozens in the course of a morning, before the sun becomes unbearably hot. We will give a smart tap to the flints so as to loosen the clay domes, wrap these up in newspapers, fill our box and go home as fast as we can, for the air will soon be as fiery as the devil’s kitchen.
Inspection, which is easier in the shade indoors, soon tells us that, though the devoured is always the wretched Mason-bee, the devourer belongs to two different species. In the one case, the cylindrical form, the creamy-white colouring and the little nipple constituting the head reveal to us the larva of the Anthrax, which does not concern us at present; in the other, the general structure and appearance betray the grub of some Hymenopteron. The Mason’s second exterminator is, in fact, a Leucopsis (Leucopsis gigas, FAB.), a magnificent insect, stripped black and yellow, with an abdomen rounded at the end and hollowed out, as is also the back, into a groove to contain a long rapier, as slender as a horsehair, which the creature unsheathes and drives through the mortar right into the cell where it proposes to establish its egg. Before occupying ourselves with its capacities as an inoculator, let us learn how its larva lives in the invaded cell.
It is a hairless, legless, sightless grub, easily confused, by inexperienced eyes, with those of various honey-gathering Hymenoptera. Its more apparent characteristics consist of a colouring like that of rancid butter, a shiny and as it were oily skin and a segmentation accentuated by a series of marked swellings, so that, when looked at from the side, the back is very plainly indented. When at rest, the larva is like a bow bending round at one point. It is made up of thirteen segments, including the head. This head, which is very small compared with the rest of the body, displays no mouth-part under the lens; at most you see a faint red streak, which calls for the microscope. You then distinguish two delicate mandibles, very short and fashioned into a sharp point. A small round mouth, with a fine piercer on the right and left, is all that the powerful instrument reveals. As for my best single magnifying-glasses, they show me nothing at all. On the other hand, we can quite easily, without arming the eye with a lens, perceive the mouth-apparatus–and particularly the mandibles–of either a honey-eater, such as an Osmia, Chalicodoma or Megachile, or a game-eater, such as a Scolia, Ammophila or Bembex. All these possess stout pincers, capable of gripping, grinding and tearing. Then what is the purpose of the Leucopsis’ invisible implements? His method of consuming will tell us.
Like his prototype, the Anthrax, the Leucopsis does not eat the Chalicodoma-grub, that is to say, he does not break it up into mouthfuls; he drains it without opening it and digging into its vitals. In him again we see exemplified that marvellous art which consists in feeding on the victim without killing it until the meal is over, so as always to have a portion of fresh meat. With its mouth assiduously applied to the unhappy creature’s skin, the lethal grub fills itself and waxes fat, while the fostering larva collapses and shrivels, retaining just enough life, however, to resist decomposition. All that remains of the decanted corpse is the skin, which, when softened in water and blown out, swells into a balloon without the least escape of gas, thus proving the continuity of the integument. All the same, the apparently unpunctured bladder has lost its contents. It is a repetition of what the Anthrax has shown us, with this difference, that the Leucopsis seems not so well skilled in the delicate work of absorbing the victim. Instead of the clean white granule which is the sole residue when the Fly has finished her joint, the insect with the long probe has a plateful of leavings, not seldom soiled with the brownish tinge of food that has gone bad. It would seem that, towards the end, the act of consumption becomes more savage and does not disdain dead meat. I also notice that the Leucopsis is not able to get up from dinner or to sit down to it again as readily as the Anthrax. I have sometimes to tease him with the point of a hair-pencil in order to make him let go; and, once he has left the joint, he hesitates a little before putting his mouth to it again. His adhesion is not the mere result of a kiss like that of a cupping- glass; it can only be explained by hooks that need releasing.
I now see the use of the microscopic mandibles. Those two delicate spikes are incapable of chewing anything, but they may very well serve to pierce the epidermis with an aperture smaller than that made by the finest needle; and it is through this puncture that the Leucopsis sucks the juices of his prey. They are instruments made to perforate the bag of fat which slowly, without suffering any internal injury, is emptied through an opening repeated here and there. The Anthrax’ cupping-glass is here replaced by piercers of exceeding sharpness and so short that they cannot hurt anything beyond the skin. Thus do we see in operation, with a different sort of implements, that wise system which keeps the provisions fresh for the consumer.
It is hardly necessary to say, to those who have read the story of the Anthrax, that this kind of feeding would be impossible with a victim whose tissues possessed their final hardness. The Mason-bee’s grub is therefore emptied by the Leucopsis’ larva while it is in a semifluid state and deep in the torpor of the nymphosis. The last fortnight in July and the first fortnight in August are the best times to witness the repast, which I have seen going on for twelve and fourteen days. Later, we find nothing in the Mason-bee’s cocoon except the Leucopsis’ larva, gloriously fat, and, by its side, a sort of thin, rancid rasher, the remains of the deceased wet-nurse. Things then remain as they are until the hot part of the following summer or at least until the end of June.
Then appears the nymph, which teaches us nothing striking; and at last the perfect insect, whose hatching may be delayed until August. Its exit from the Mason’s fortress has no likeness to the strange method employed by the Anthrax. Endowed with stout mandibles, the perfect insect splits the ceiling of its abode by itself without much difficulty. At the time of its deliverance, the Mason-bees, who work in May, have long disappeared. The nests on the pebbles are all closed, the provisioning is finished, the larvae are sleeping in their yellow cocoons. As the old nests are utilized by the Mason so long as they are not too much dilapidated, the dome which has just been vacated by the Leucopsis, now more than a year old, has its other cells occupied by the Bee’s children. There is here, without seeking farther, a fat living for the Leucopsis’ offspring which she well knows how to turn to profit. It depends but on herself to make the house in which she was born into the residence of her family. Besides, if she has a fancy for distant exploration, clay domes abound in the harmas. The inoculation of the eggs through the walls will begin shortly. Before witnessing this curious performance, let us examine the needle that is to effect it.
The insect’s abdomen is hollowed, at the top, into a furrow that runs up to the base of the thorax; the end, which is broader and rounded, has a narrow slit, which seems to divide this region into two. The whole thing suggests a pulley with a fine groove. When at rest, the inoculating-needle or ovipositor remains packed in the slit and the furrow. The delicate instrument thus almost completely encircles the abdomen. Underneath, on the median line, we see a long, dark-brown scale, pointed, keel-shaped, fixed by its base to the first abdominal segment, with its sides prolonged into membranous wings which are fastened tightly to the insect’s flanks. Its function is to protect the underlying region, a soft-walled region in which the probe has its source. It is a cuirass, a lid which protects the delicate motor- machinery during periods of inactivity but swings from back to front and lifts when the implement has to be unsheathed and used.
We will now remove this lid with the scissors, so as to have the whole apparatus before our eyes, and then raise the ovipositor with the point of a needle. The part that runs along the back comes loose without the slightest difficulty, but the part embedded in the groove at the end of the abdomen offers a resistance that warns us of a complication which we did not notice at first. The tool, in fact, consists of three pieces, a central piece, or inoculating-filament, and two side-pieces, which together constitute a scabbard. The two latter are more substantial, are hollowed out like the sides of a groove and, when uniting, form a complete groove in which the filament is sheathed. This bivalvular scabbard adheres loosely to the dorsal part; but, farther on, at the tip of the abdomen and under the belly, it can no longer be detached, as its valves are welded to the abdominal wall. Here, therefore, we find, between the two joined protecting parts, a simple trench in which the filament lies covered up. As for this filament, it is easily extracted from its sheath and released down to its base, under the shield formed by the scale.
Seen under the magnifying-glass, it is a round, stiff, horny thread, midway in thickness between a human hair and a horse-hair. Its tip is a little rough, pointed and bevelled to some length down. The microscope becomes necessary if we would see its real structure, which is much less simple than it at first appears. We perceive that the bevelled end-part consists of a series of truncated cones, fitting one into the other, with their wide base slightly projecting. This arrangement produces a sort of file, a sort of rasp with very much blunted teeth. When pressed on the slide, the thread divides into four pieces of unequal length. The two longer end in the toothed bevel. They come together in a very narrow groove, which receives the two other, rather shorter pieces. These both end in a point, which, however, is not toothed and does not project as far as the final rasp. They also unite to form a groove, which fits into the groove of the other two, the whole constituting a complete channel or duct. Moreover, the two shorter pieces, considered together, can move, lengthwise, in the groove that receives them; they can also move one over the other, always lengthwise, so much so that, on the slide of the microscope, their terminal points are seldom situated on the same level.
If with our scissors we cut a piece of the inoculating-thread from the living insect and examine the section under the magnifying-glass, we shall see the inner groove lengthen out and project beyond the outer groove and then go in again in turn, while from the wound there oozes a tiny albimunous drop, doubtless proceeding from the liquid that gives the egg the singular appendage to which we shall come presently. By means of these longitudinal movements of the inner trench inside the outer trench and of the sliding, one over the other, of the two portions of the former, the egg can be despatched to the end of the ovipositor notwithstanding the absence of any muscular contraction, which is impossible in a horny conduit.
We have only to press the upper surface of the abdomen to see it disjoint itself from the first segment, as though the insect had been cut almost in two at that point. A wide gap or hiatus appears between the first and second rings; and, under a thin membrane, the base of the ovipositor bulges out, bent back into a stout hook. Here the filament passes through the insect from end to end and emerges underneath. Its issue is therefore near the base of the abdomen, instead of at the tip, as usual. This curious arrangement has the effect of shortening the lever-arm of the ovipositor and bringing the starting-point of the filament nearer to the fulcrum, namely, the legs of the insect, and of thus assisting the difficult task of inoculation by making the most of the effort expended.
To sum up, the ovipositor when at rest goes round the abdomen. Starting at the base, on the lower surface, it runs round the belly from front to back and then returns from back to front on the upper surface, where it ends at almost the same level as its starting-point. Its length is 14 millimetres. (.546 inch–Translator’s Note.) This fixes the limit of the depth which the probe is able to reach in the Mason-bee’s nests.
One last word on the Leucopsis’ weapon. In the dying insect, beheaded, stripped of legs and wings, with a pin stuck through its body, the sides of the fissure containing the inoculating-thread quiver violently, as if the belly were going to open, divide in two along the median line and then reunite its two halves. The thread itself gives convulsive tremblings; it comes out of its scabbard, goes back and slips out again. It is as though the laying-implement could not persuade itself to die before accomplishing its mission. The insect’s supreme aim is the egg; and, so long as the least spark of life remains, it makes dying efforts to lay.
Leucopsis gigas exploits the nests of the Mason-bee of the Pebbles and the Mason-bee of the Sheds with equal zest. To observe the insertion of the egg at my ease and to watch the operator at work over and over again, I gave the preference to the last-named Mason, whose nests, removed from the neighbouring roofs by my orders, have hung for some years in the arch of my basement. These clay hives fastened to tiles supply me with fresh records each summer. I am much indebted to them in the matter of the Leucopsis’ life-history.
By way of comparison with what took place under my roof, I used to observe the same scenes on the pebbles of the surrounding wastelands. My excursions, alas, did not all reward my zeal, which zeal was not without merit in the merciless sunshine; but still, at rare intervals, I succeeded in seeing some Leucopsis digging her probe into the mortar dome. Lying flat on the ground, from the beginning to the end of the operation, which sometimes lasted for hours, I closely watched the insect in its every movement, while my Dog, weary of being out of doors in that scorching heat, would discreetly retire from the fray and, with his tail between his legs and his tongue hanging out, go home and stretch himself at full length on the cool tiles of the hall. How wise he was to scorn this pebble-gazing! I would come in half- roasted, as brown as a berry, to find my friend Bull wedged into a corner, his back to the wall, sprawling on all fours, while, with heaving sides, he panted forth the last sprays of steam from his overheated interior. Yes, he was much better-advised to return as fast as he could to the shade of the house. Why does man want to know things? Why is he not indifferent to them, with the lofty philosophy of the animals? What interest can anything have for us that does not fill our stomachs? What is the use of learning? What is the use of truth, when profit is all that matters? Why am I–the descendant, so they tell me, of some tertiary Baboon–afflicted with the passion for knowledge from which Bull, my friend and companion, is exempt? Why…oh, where have I got to? I was going in, wasn’t I, with a splitting headache? Quick, let us get back to our subject!
It was in the first week of July that I saw the inoculation begin on my Chalicodoma sicula nests. The parasite is at her task in the hottest part of the day, close on three o’clock in the afternoon; and work goes on almost to the end of the month, decreasing gradually in activity. I count as many as twelve Leucopses at a time on the most thickly-populated pair of tiles. The insect slowly and awkwardly explores the nests. It feels the surface with its antennae, which are bent at a right angle after the first joint. Then, motionless, with lowered head, it seems to meditate and to debate within itself on the fitness of the spot. Is it here or somewhere else that the coveted larva lies? There is nothing outside, absolutely nothing, to tell us. It is a stony expanse, bumpy but yet very uniform in appearance, for the cells have disappeared under a layer of plaster, a work of public interest to which the whole swarm devotes its last days. If I myself, with my long experience, had to decide upon the suitable point, even if I were at liberty to make use of a lens for examining the mortar grain by grain and to auscultate the surface in order to gather information from the sound emitted, I should decline the job, persuaded in advance that I should fail nine times out of ten and only succeed by chance.
Where my discernment, aided by reason and my optical contrivances, fails, the insect, guided by the wands of its antennae, never blunders. Its choice is made. See it unsheathing its long instrument. The probe points normally towards the surface and occupies nearly the central spot between the two middle-legs. A wide dislocation appears on the back, between the first and second segments of the abdomen; and the base of the instrument swells like a bladder through this opening; while the point strives to penetrate the hard clay. The amount of energy expended is shown by the way in which the bladder quivers. At every moment we expect to see the frail membrane burst with the violence of the effort. But it does not give way; and the wire goes deeper and deeper.
Raising itself high on its legs, to give free play to its apparatus, the insect remains motionless, the only sign of its arduous labours being a slight vibration. I see some perforators who have finished operating in a quarter of an hour. These are the quickest at the business. They have been lucky enough to come across a wall which is less thick and less hard than usual. I see others who spend as many as three hours on a single operation, three long hours of patient watching for me, in my anxiety to follow the whole performance to the end, three long hours of immobility for the insect, which is even more anxious to make sure of board and lodging for its egg. But then is it not a task of the utmost difficulty to introduce a hair into the thickness of a stone? To us, with all the dexterity of our fingers, it would be impossible; to the insect, which simply pushes with its belly, it is just hard work.
Notwithstanding the resistance of the substance traversed, the Leucopsis perseveres, certain of succeeding; and she does succeed, although I am still unable to understand her success. The material through which the probe has to penetrate is not a porous substance; it is homogeneous and compact, like our hardened cement. In vain do I direct my attention to the exact point where the instrument is at work; I see no fissure, no opening that can facilitate access. A miner’s drill penetrates the rock only by pulverizing it. This method is not admissible here; the extreme delicacy of the implement is opposed to it. The frail stem requires, so it seems to me, a ready- made way, a crevice through which it can slip; but this crevice I have never been able to discover. What about a dissolving fluid which would soften the mortar under the point of the ovipositor? No, for I see not a trace of humidity around the point where the thread is at work. I fall back upon a fissure, a lack of continuity somewhere, although my examination fails to discover any on the Mason-bee’s nest. I was better served in another case. Leucopsis dorsigera, FAB., settles her eggs on the larva of the Diadem Anthidium, who sometimes makes her nest in reed-stumps. I have repeatedly seen her insert her auger through a slight rupture in the side of the reed. As the wall was different, wood in the latter case and mortar in the former, perhaps it will be best to look upon the matter as a mystery.
My sedulous attendance, during the best part of July, in front of the tiles hanging from the walls of the arch, allowed me to reckon the inoculations. Each time that the insect, on finishing the operation, removed its probe, I marked in pencil the exact point at which the instrument was withdrawn; and I wrote down the date beside it. This information was to be utilized when the Leucopsis finished her labours.
When the perforators are gone, I proceed with my examination of the nests, covered with my hieroglyphics, the pencilled notes. One result, one which I fully expected, compensates me straightway for all my weary waitings. Under each spot marked in black, under each spot whence I saw the ovipositor withdrawn, I always find a cell, with not a single exception. And yet there are intervals of solid stone between the cells: the partition-walls alone would account for some. Moreover, the compartments, which are very irregularly disposed by a swarm of toilers who all work in their own sweet way, have great irregular cavities between them, which end by being filled up with the general plastering of the nest. The result of this arrangement is that the massive portions cover almost the same space as the hollow portions. There is nothing outside to show whether the underlying regions are full or empty. It is quite impossible for me to decide if, by digging straight down, I shall come to a hollow cell or to a solid wall.
But the insect makes no mistake: the excavations under my pencil-marks bear witness to that; it always directs its apparatus towards the hollow of a cell. How is it apprised whether the part below is empty or full? Its organs of information are undoubtedly the antennae, which feel the ground. They are two fingers of unparalleled delicacy, which pry into the basement by tapping on the part above it. Then what do those puzzling organs perceive? A smell? Not at all; I always had my doubts of that and now I am certain of the contrary, after what I shall describe in a moment. Do they perceive a sound? Are we to treat them as a superior kind of microphone, capable of collecting the infinitesimal echoes of what is full and the reverberations of what is empty? It is an attractive idea, but unfortunately the antennae play their part equally well on a host of occasions when there are no vaults to reverberate. We know nothing and are perhaps destined never to know anything of the real value of the antennal sense, to which we have nothing analogous; but, though it is impossible for us to say what it does perceive, we are at least able to recognize to some extent what it does not perceive and, in particular, to deny it the faculty of smell.
As a matter of fact, I notice, with extreme surprise, that the great majority of the cells visited by the Leucopsis’ probe do not contain the one thing which the insect is seeking, namely, the young larva of the Mason-bee enclosed in its cocoon. Their contents consist of the refuse so often met with in old Chalicodoma-nests: liquid honey left unemployed, because the egg has perished; spoilt provisions, sometimes mildewed, or sometimes a tarry mass; a dead larva, stiffened into a brown cylinder; the shrivelled corpse of a perfect insect, which lacked the strength to effect its deliverance; dust and rubbish which has come from the exit-window afterwards closed up by the outer coating of plaster. The odoriferous effluvia that can emanate from these relics certainly possess very diverse characters. A sense of smell with any subtlety at all would not be deceived by this stuff, sour, ‘high,’ musty or tarry as the case may be; each compartment, according to its contents, has a special aroma, which we might or might not be able to perceive; and this aroma most certainly bears no resemblance to that which we may assume the much-desired fresh larva to possess. If nevertheless the Leucopsis does not distinguish between these various cells and drives the probe into all of them indifferently, is this not an evident proof that smell is no guide whatever to her in her search? Other considerations, when I was treating of the Hairy Ammophila, enabled me to assert that the antennae have no olfactory powers. To-day, the frequent mistakes of the Leucopsis, whose antennae are nevertheless constantly exploring the surface, make this conclusion absolutely certain.
The perforator of clay nests has, so it seems to me, delivered us from an old physiological fallacy. She would deserve studying, if for no other result than this; but her interest is far from being exhausted. Let us look at her from another point of view, whose full importance will not be apparent until the end; let us speak of something which I was very far from suspecting when I was so assiduously watching the nests of my Mason-bees.
The same cell can receive the Leucopsis’ probe a number of times, at intervals of several days. I have said how I used to mark in black the exact place at which the laying-implement had entered and how I wrote the date of the operation beside it. Well, at many of these already visited spots, concerning which I possessed the most authentic documents, I saw the insect return a second, a third and even a fourth time, either on the same day or some while after, and drive its inoculating-thread in again, at precisely the same place, as though nothing had happened. Was it the same individual repeating her operation in a cell which she had visited before but forgotten, or different individuals coming one after the other to lay an egg in a compartment thought to be unoccupied? I cannot say, having neglected to mark the operators, for fear of disturbing them.
As there is nothing, except the mark of my pencil, a mark devoid of meaning to the insect, to indicate that the auger has already been at work there, it may easily happen that the same operator, finding under her feet a spot already exploited by herself but effaced from her memory, repeats the thrust of her tool in a compartment which she believes herself to be discovering for the first time. However retentive its memory for places may be, we cannot admit that the insect remembers for weeks on end, as well as point by point, the topography of a nest covering a surface of some square yards. Its recollections, if it have any, serve it badly; the outward appearance gives it no information; and its drill enters wherever it may happen to discover a cell, at points that have already perhaps been pierced several times over.
It may also happen–and this appears to me the most frequent case– that one exploiter of a cell is succeeded by a second, a third, a fourth and others still, all fired with the newcomer’s zeal because their predecessors have left no trace of their passage. In one way or another, the same cell is exposed to manifold layings, though its contents, the Chalicodoma-grub, be only the bare ration of a single Leucopsis-grub.
These reiterated borings are not at all rare: I noted a score of them on my tiles; and, in the case of some cells, the operation was repeated before my eyes as often as four times. Nothing tells us that this number was not exceeded in my absence. The little that I observed prevents me from fixing any limit. And now a momentous question arises: is the egg really laid each time that the probe enters a cell? I can see not the slightest excuse for supposing the contrary. The ovipositor, because of its horny nature, can have but a very dull sense of touch. The insect is apprised of the contents of the cell only by the end of that long horse-hair, a not very trustworthy witness, I should imagine. The absence of resistance tells it that it has reached an empty space; and this is probably the only information that the insensible implement can supply. The drill boring through the rock cannot tell the miner anything about the contents of the cavern which it has entered; and the case must be the same with the rigid filament of the Leucopses.
Now that the thread has reached its goal, what does the cell contain? Mildewed honey, dust and rubbish, a shrivelled larva, or a larva in good condition? Above all, does it already contain an egg? This last question calls for a definite answer, but as a matter of fact it is impossible for the insect to learn anything from a horse-hair on that most delicate matter, the presence or absence of an egg, a mere atom of a thing, in that vast apartment. Even admitting some sense of touch at the end of the drill, one insuperable difficulty would always remain: that of finding the exact spot where the tiny speck lies in those spacious and mysterious regions. I go so far as to believe that the ovipositor tells the insect nothing, or at any rate very little, of the inside of the cell, whether propitious or not to the development of the germ. Perhaps each thrust of the instrument, provided that it meets with no resistance from solid matter, lays the egg, to whose lot there falls at one time good, wholesome food, at another mere refuse.
These anomalies call for more conclusive proofs than the rough deductions drawn from the nature of the horny ovipositor. We must ascertain in a direct fashion whether the cell into which the auger has been driven several times over actually contains several occupants in addition to the larva of the Mason-bee. When the Leucopses had finished their borings, I waited a few days longer so as to give the young grubs time to develop a little, which would make my examination easier. I then moved the tiles to the table in my study, in order to investigate their secrets with the most scrupulous care. And here such a disappointment as I have rarely known awaited me. The cells which I had seen, actually seen, with my own eyes, pierced by the probe two or three or even four times, contained but one Leucopsis-grub, one alone, eating away at its Chalicodoma. Others, which had also been repeatedly probed, contained spoilt remnants, but never a Leucopsis. O holy patience, give me the courage to begin again! Dispel the darkness and deliver me from doubt!
I begin again. The Leucopsis-grub is familiar to me; I can recognize it, without the possibility of a mistake, in the nests of both the Chalicodoma of the Pebbles and the Chalicodoma of the Sheds. All through the winter, I rush about, getting my nests from the roofs of old sheds and the pebbles of the waste-lands; I stuff my pockets with them, fill my box, load Favier’s knapsack; I collect enough to litter all the tables in my study; and, when it is too cold out of doors, when the biting mistral blows, I tear open the fine silk of the cocoons to discover the inhabitant. Most of them contain the Mason in the perfect state; others give me the larva of the Anthrax; others– very numerous, these–give me the larva of the Leucopsis. And this last is alone, always alone, invariably alone. The whole thing is utterly incomprehensible when one knows, as I know, how many times the probe entered those cells.
My perplexity only increases when, on the return of summer, I witness for the second time the Leucopsis’ repeated operations on the same cells and for the second time find a single larva in the compartments which have been bored several times over. Shall I then be forced to accept that the auger is able to recognize the cells already containing an egg and that it thenceforth refrains from laying there? Must I admit an extraordinary sense of touch in that bit of horse- hair, or even better, a sort of divination which declares where the egg lies without having to touch it? But I am raving! There is certainly something that escapes me; and the obscurity of the problem is simply due to my incomplete information. O patience, supreme virtue of the observer, come to my aid once more! I must begin all over again for the third time.
Until now, my investigations have been made some time after the laying, at a period when the larva is at least fairly developed. Who knows? Something perhaps happens, at the very commencement of infancy, that may mislead me afterwards. I must apply to the egg itself if I would learn the secret which the grub will not reveal. I therefore resume my observations in the first fortnight of July, when the Leucopses are beginning to visit busily both Mason-bee’s nests. The pebbles in the waste-lands supply me with plenty of buildings of the Chalicodoma of the Walls; the byres scattered here and there in the fields give me, under their dilapidated roofs, in fragments broken off with the chisel, the edifices of the Chalicodoma of the Sheds. I am anxious not to complete the destruction of my home hives, already so sorely tried by my experiments; they have taught me much and can teach me more. Alien colonies, picked up more or less everywhere, provide me with my booty. With my lens in one hand and my forceps in the other, I go through my collection on the same day, with the prudence and care which only the laboratory-table permits. The results at first fall far short of my expectations. I see nothing that I have not seen before. I make fresh expeditions, after a few days’ interval; I bring back fresh loads of lumps of mortar, until at last fortune smiles upon me.
Reason was not at fault. Each thrust means the laying of an egg when the probe reaches the cell. Here is a cocoon of the Mason-bee of the Pebbles with an egg side by side with the Chalicodoma-grub. But what a curious egg! Never have my eyes beheld the like; and then is it really the egg of the Leucopsis? Great was my apprehension. But I breathed again when I found, a couple of weeks later, that the egg had become the larva with which I was familiar. Those cocoons with a single egg are as numerous as I can wish; they exceed my wishes: my little glass receptacles are too few to hold them.
And here are others, more precious ones still, with manifold layings. I find plenty with two eggs; I find some with three or four; the best- colonised offer me as many as five. And, to crown my delight, the joy of the seeker to whom success comes at the last moment, when he is on the verge of despair, here again, duly furnished with an egg, is a sterile cocoon, that is to say, one containing only a shrivelled and decaying larva. All my suspicions are confirmed, down to the most inconsequent: the egg housed with a mass of putrefaction.
The nests of the Mason-bee of the Walls are the more regular in structure and are easier to examine, because their base is wide open once it is separated from the supporting pebble; and it was these which supplied me with by far the greater part of my information. Those of the Mason-bee of the Sheds have to be chipped away with a hammer before one can inspect their cells, which are heaped up anyhow; and they do not lend themselves anything like so well to delicate investigations, as they suffer both from the shock and the ill- treatment.
And now the thing is done: it remains certain that the Leucopsis’ laying is exposed to very exceptional dangers. She can entrust the egg to sterile cells, without provisions fit to use; she can establish several in the same cell, though this cell contains nourishment for one only. Whether they proceed from a single individual returning several times, by inadvertence, to the same place, or are the work of different individuals unaware of the previous borings, those multiple layings are very frequent, almost as much so as the normal layings. The largest which I have noticed consisted of five eggs, but we have no authority for looking upon this number as an outside limit. Who could say, when the perforators are numerous, to what lengths this accumulation can go? I will set forth on some future occasion how the ration of one egg remains in reality the ration of one egg, despite the multiplicity of banqueters.
I will end by describing the egg, which is a white, opaque object, shaped like a much-elongated oval. One of the ends is lengthened out into a neck or pedicle, which is as long as the egg proper. This neck is somewhat wrinkled, sinuous and as a rule considerably curved. The whole thing is not at all unlike certain gourds with an elongated paunch and a snake-like neck. The total length, pedicle and all, is about 3 millimetres. (About one-eighth of an inch.–Translator’s Note.) It is needless to say, after recognizing the grub’s manner of feeding, that this egg is not laid inside the fostering larva. Yet, before I knew the habits of the Leucopsis, I would readily have believed that every Hymenopteron armed with a long probe inserts her eggs into the victim’s sides, as the Ichneumon-flies do to the Caterpillars. I mention this for the benefit of any who may be under the same erroneous impression.
The Leucopsis’ egg is not even laid upon the Mason-bee’s larva; it is hung by its bent pedicle to the fibrous wall of the cocoon. When I go to work very delicately, so as not to disturb the arrangement in knocking the nest off its support, and then extract and open the cocoon, I see the egg swinging from the silken vault. But it takes very little to make it fall. And so, most often, even though it be merely the effect of the shock sustained when the nest is removed from its pebble, I find the egg detached from its suspension-point and lying beside the larva, to which it never adheres in any circumstances. The Leucopsis’ probe does not penetrate beyond the cocoon traversed; and the egg remains fastened to the ceiling, in the crook of some silky thread, by means of its hooked pedicle.
INDEX.
Amazon Ant (see Red Ant).
Ammophila.
Ammophila hirsuta (see Hairy Ammophila).
Ant (see also Black Ant, Red Ant).
Anthidium (see also Cotton-bee, Diadem Anthidium).
Anthophora (see also Hairy-footed Anthophora).
Anthrax (see also Anthrax sinuata).
Anthrax sinuata.
Anthrenus.
Ape.
Aphis.
Baboon.
Bastien.
Bee.
Bembex (see also Bembex rostrata).
Bembex rostrata.
Black Ant.
Blanchard, Emile.
Blue Osmia.
Bombylius.
Bumble-bee.
Butterfly.
Cabbage-caterpillar.
Cagliostro.
Carrier-pigeon.
Castelnau de la Porte, Francis Comte de.
Cat.
Caterpillar (see also Cabbage-caterpillar, Grey Worm, Processionary Caterpillar, Spurge-caterpillar).
Cerceris (see also Great Cerceris).
Cerceris tuberculata (see Great Cerceris).
Cetonia.
Chalcis.
Chalicodoma (see Mason-bee).
Chalicodoma muraria (see Mason-bee of the Walls).
Chalicodoma pyrenaica, C. pyrrhopeza, C. rufitarsis, C. sicula (see Mason-bee of the Sheds).