And what does the Halictus mother do in this disaster? She is free to visit her grubs at any moment; she has but to put her head into the passage of the house: she cannot fail to be apprised of their distress. The squandered loaf, the swarming mass of vermin tell their own tale. Why does she not take the intruders by the skin of the abdomen? To grind them to powder with her mandibles, to fling them out of doors were the business of a second. And the foolish creature never thinks of it, leaves the ravagers in peace!
She does worse. When the time of the nymphosis comes, the Halictus mother goes to the cells rifled by the parasite and closes them with an earthen plug as carefully as she does the rest. This final barricade, an excellent precaution when the cot is occupied by an Halictus in course of metamorphosis, becomes the height of absurdity when the Gnat has passed that way. Instinct does not hesitate in the face of this ineptitude: it seals up emptiness. I say, emptiness, because the crafty maggot hastens to decamp the instant that the victuals are consumed, as though it foresaw an insuperable obstacle for the coming Fly: it quits the cell before the Bee closes it.
To rascally guile the parasite adds prudence. All, until there is none of them left, abandon the clay homes which would be their undoing once the entrance was plugged up. The earthen niche, so grateful to the tender skin, thanks to its polished coating, so free from humidity, thanks to its waterproof glaze, ought, one would think, to make an excellent waiting-place. The maggots will have none of it. Lest they should find themselves walled in when they become frail Gnats, they go away and disperse in the neighbourhood of the ascending shaft.
My digging operations, in fact, always reveal the pupae outside the cells, never inside. I find them enshrined, one by one, in the body of the clayey earth, in a narrow recess which the emigrant worm has contrived to make for itself. Next spring, when the hour comes for leaving, the adult insect has but to creep through the rubbish, which is easy work.
Another and no less imperative reason compels this change of abode on the parasite's part. In July, a second generation of the Halictus is procreated. The Gnat, reduced on her side to a single brood, remains in the pupa state and awaits the spring of the following year before effecting her transformation. The honey-gather resumes her work in her native village; she avails herself of the pits and cells constructed in the spring, saving no little time thereby. The whole elaborate structure has remained in good condition. It needs but a few repairs to make the old house habitable.
Now what would happen if the Bee, so scrupulous in matters of cleanliness, were to find a pupa in the cell which she is sweeping?
She would treat the cumbersome object as she would a piece of old plaster. It would be no more to her than any other refuse, a bit of gravel, which, seized with the mandibles, crushed perhaps, would be sent to join the rubbish-heap outside. Once removed from the soil and exposed to the inclemencies of the weather, the pupa would inevitably perish.
I admire this intelligent foresight of the maggot, which forgoes the comfort of the moment for the security of the future. Two dangers threaten it: to be immured in a casket whence the Fly can never issue; or else to die out of doors, in the unkindly air, when the Bee sweeps out the restored cells. To avoid this twofold peril, it decamps before the door is closed, before the July Halictus sets her house in order.
