Certain hunting Hymenoptera, the Bembex-wasps, for instance, are accustomed to furnish the provisions in instalments: so that the grub may have fresh though dead game, they fill the platter each day. The Halictus mother has not these domestic necessities, as her provisions keep more easily; but still she might well distribute a second portion of flour to the larvae, when their appetite attains its height. I can see nothing else to explain the open doors of the cells during the feeding-period.
At last the grubs, close-watched and fed to repletion, have achieved the requisite degree of fatness; they are on the eve of being transformed into pupae. Then and not till then the cells are closed: a big clay stopper is built by the mother into the spreading mouth of the jug. Henceforth the maternal cares are over. The rest will come of itself.
Hitherto we have witnessed only the peaceful details of the housekeeping. Let us go back a little and we shall be witnesses of rampant brigandage. In May, I visit my most populous village daily, at about ten o'clock in the morning, when the victualling-operations are in full swing. Seated on a low chair in the sun, with my back bent and my arms upon my knees, I watch, without moving, until dinner-time. What attracts me is a parasite, a trumpery Gnat, the bold despoiler of the Halictus.
Has the jade a name? I trust so, without, however, caring to waste my time in enquiries that can have no interest for the reader. Facts clearly stated are preferable to the dry minutiae of nomenclature. Let me content myself with giving a brief description of the culprit. She is a Dipteron, or Fly, five millimetres long. (.195 inch.—Translator's Note.) Eyes, dark-red; face, white. Corselet, pearl-grey, with five rows of fine black dots, which are the roots of stiff bristles pointing backwards. Greyish belly, pale below. Black legs.
She abounds in the colony under observation. Crouching in the sun, near a burrow, she waits. As soon as the Halictus arrives from her harvesting, her legs yellow with pollen, the Gnat darts forth and pursues her, keeping behind her in all the turns of her oscillating flight. At last, the Bee suddenly dives indoors. No less suddenly the other settles on the mole-hill, quite close to the entrance. Motionless, with her head turned towards the door of the house, she waits for the Bee to finish her business. The latter reappears at last and, for a few seconds, stands on the threshold, with her head and thorax outside the hole. The Gnat, on her side, does not stir.
Often, they are face to face, separated by a space no wider than a finger's breadth. Neither of them shows the least excitement. The Halictus—judging, at least, by her tranquillity—takes no notice of the parasite lying in wait for her; the parasite, on the other hand, displays no fear of being punished for her audacity. She remains imperturbable, she, the dwarf, in the presence of the colossus who could crush her with one blow.
In vain I watch anxiously for some sign of apprehension on either side: nothing in the Halictus points to a knowledge of the danger run by her family; nor does the Gnat betray any dread of swift retribution. Plunderer and plundered stare at each other for a moment; and that is all.
If she liked, the amiable giantess could rip up with her claw the tiny bandit who ruins her home; she could crunch her with her mandibles, run her through with her stiletto. She does nothing of the sort, but leaves the robber in peace, to sit quite close, motionless, with her red eyes fixed on the threshold of the house. Why this fatuous clemency?
The Bee flies off. Forthwith, the Gnat walks in, with no more ceremony than if she were entering her own place. She now chooses among the victualled cells at her ease, for they are all open, as I have said; she leisurely deposits her eggs. No one will disturb her until the Bee's return. To flour one's legs with pollen, to distend one's crop with syrup is a task that takes long a-doing; and the intruder, therefore, has time and to spare wherein to commit her felony. Moreover, her chronometer is well-regulated and gives the exact measure of the Bee's length of absence. When the Halictus comes back from the fields, the Gnat has decamped. In some favourable spot, not far from the burrow, she awaits the opportunity for a fresh misdeed.
What would happen if a parasite were surprised at her work by the Bee? Nothing serious. I see them, greatly daring, follow the Halictus right into the cave and remain there for some time while the mixture of pollen and honey is being prepared. Unable to make use of the paste so long as the harvester is kneading it, they go back to the open air and wait on the threshold for the Bee to come out. They return to the sunlight, calmly, with unhurried steps: a clear proof that nothing untoward has occurred in the depths where the Halictus works.