Social Life in the Insect World

by Jean-Henri Fabre

Every one will understand the vagueness which fills the observer's mind in respect of such a question as this. The reader has the right to be doubtful. I will spare him my suspicions, my gropings for the truth, and the checks encountered in the search, and give him the results of my long inquiry. Everything has its appropriate and harmonious reason. I am too fully persuaded of this to believe that the Philanthus commits her profanation of corpses merely to satisfy her appetite. What does the empty stomach mean? May it not—Yes!—But, after all, who knows? Well, let us follow up the scent.

The first care of the mothers is the welfare of the family. So far all we know of the Philanthus concerns her talent for murder. Let us consider her as a mother. We have seen her hunt on her own account; let us now watch her hunt for her offspring, for the race. Nothing is simpler than to distinguish between the two kinds of hunting. When the insect wants a few good mouthfuls of honey and nothing else, she abandons the bee contemptuously when she has emptied its stomach. It is so much valueless waste, which will shrivel where it lies and be dissected by ants. If, on the other hand, she intends to place it in the larder as a provision for her larvæ, she clasps it with her two intermediate legs, and, walking on the other four, drags it to and fro along the edge of the bell-glass in search of an exit so that she may fly off with her prey. Having recognised the circular wall as impassable, she climbs its sides, now holding the bee in her mandibles by the antennæ, clinging as she climbs to the vertical polished surface with all six feet. She gains the summit of the glass, stays for a little while in the flask-like cavity of the terminal button or handle, returns to the ground, and resumes her circuit of the glass and her climbing, relinquishing the bee only after an obstinate attempt to escape with it. The persistence with which the Philanthus retains her clasp upon the encumbering burden shows plainly that the game would go straight to the larder were the insect at liberty.

Those bees intended for the larvæ are stung under the chin like the others; they are true corpses; they are manipulated, squeezed, exhausted of their honey, just as the others. There is no difference in the method of capture nor in their after-treatment.

As captivity might possibly result in a few anomalies of action, I decided to inquire how matters went forward in the open. In the neighbourhood of some colonies of Philanthidæ I lay in wait, watching for perhaps a longer time than the question justified, as it was already settled by what occurred in captivity. My scrupulous watching at various times was rewarded. The majority of the hunters immediately entered their nests, carrying the bees pressed against their bodies; some halted on the neighbouring undergrowth; and these I saw treating the bee in the usual manner, and lapping the honey from its mouth. After these preparations the corpse was placed in the larder. All doubt was thus destroyed: the bees provided for the larvæ are previously carefully emptied of their honey.

Since we are dealing with the subject, let us take the opportunity of inquiring into the customs of the Philanthus in a state of freedom. Making use of her victims when absolutely lifeless, so that they would putrefy in the course of a few days, this hunter of bees cannot adopt the customs of certain insects which paralyse their prey, and fill their cellars before laying an egg. She must surely be obliged to follow the method of the Bembex, whose larva receives, at intervals, the necessary nourishment; the amount increasing as the larva grows. The facts confirm this deduction. I spoke just now of the tediousness of my watching when watching the colonies of the Philanthus. It was perhaps even more tedious than when I was keeping an eye upon the Bembex. Before the burrows of Cerceris tuberculus and other devourers of the weevil, and before that of the yellow-winged Sphex, the slayer of crickets, there is plenty of distraction, owing to the busy movements of the community. The mothers have scarcely entered the nest before they are off again, returning quickly with fresh prey, only to set out once more. The going and coming is almost continuous until the storehouse is full.

The burrows of the Philanthus know nothing of such animation, even in a populous colony. In vain my vigils prolonged themselves into whole mornings or afternoons, and only very rarely does the mother who has entered with a bee set forth upon a second expedition. Two captures by the same huntress is the most that I have seen in my long watches. Once the family is provided with sufficient food for the moment the mother postpones further hunting trips until hunting becomes necessary, and busies herself with digging and burrowing in her underground dwelling. Little cells are excavated, and I see the rubbish from them gradually pushed up to the surface. With that exception there is no sign of activity; it is as though the burrow were deserted.

To lay the nest bare is not easy. The burrow penetrates to a depth of about three feet in a compact soil; sometimes in a vertical, sometimes in a horizontal direction. The spade and pick, wielded by hands more vigorous but less expert than my own, are indispensable; but the conduct of the excavation is anything but satisfactory. At the extremity of the long gallery—it seems as though the straw I use for sounding would never reach the end—we finally discover the cells, egg-shaped cavities with the longer axis horizontal. Their number and their mutual disposition escape me.

Some already contain the cocoon—slender and translucid, like that of the Cerceris, and, like it, recalling the shape of certain homœopathic phials, with oval bodies surmounted by a tapering neck. By the extremity of the neck, which is blackened and hardened by the dejecta of the larvæ, the cocoon is fixed to the end of the cell without any other support. It reminds one of a short club, planted by the end of the handle, in a line with the horizontal axis of the cell. Other cells contain the larva in a stage more or less advanced. The grub is eating the last victim proffered; around it lie the remains of food already consumed. Others, again, show me a bee, a single bee, still intact, and having an egg deposited on the under-side of the thorax. This bee represents the first instalment of rations; others will follow as the grub matures. My expectations are thus confirmed; as with Bembex, slayer of Diptera, so Philanthus, killer of bees, lays her egg upon the first body stored, and completes, at intervals, the provisioning of the cells.

The problem of the dead bee is elucidated; there remains the other problem, of incomparable interest—Why, before they are given over to the larvæ, are the bees robbed of their honey? I have said, and I repeat, that the killing and emptying of the bee cannot be explained solely by the gluttony of the Philanthus. To rob the worker of its booty is nothing; such things are seen every day; but to slaughter it in order to empty its stomach—no, gluttony cannot be the only motive. And as the bees placed in the cells are squeezed dry no less than the others, the idea occurs to me that as a beefsteak garnished with confitures is not to every one's taste, so the bee sweetened with honey may well be distasteful or even harmful to the larvæ of the Philanthus. What would the grub do if, replete with blood and flesh, it were to find under its mandibles the honey-bag of the bee?—if, gnawing at random, it were to open the bees stomach and so drench its game with syrup? Would it approve of the mixture? Would the little ogre pass without repugnance from the gamey flavour of a corpse to the scent of flowers? To affirm or deny is useless. We must see. Let us see.

I take the young larvæ of the Philanthus, already well matured, but instead of serving them with the provisions buried in their cells I offer them game of my own catching—bees that have filled themselves with nectar among the rosemary bushes. My bees, killed by crushing the head, are thankfully accepted, and at first I see nothing to justify my suspicions. Then my nurslings languish, show themselves disdainful of their food, give a negligent bite here and there, and finally, one and all, die beside their uncompleted meal. All my attempts miscarry; not once do I succeed in rearing my larvæ as far as the stage of spinning the cocoon. Yet I am no novice in my duties as dry-nurse. How many pupils have passed through my hands and have reached the final stage in my old sardine-boxes as well as in their native burrows! I shall draw no conclusions from this check, which my scruples may attribute to some unknown cause. Perhaps the atmosphere of my cabinet and the dryness of the sand serving them for a bed have been too much for my nurslings, whose tender skins are used to the warm moisture of the subsoil. Let us try another method.