Has the jade a name? I like to think so, without, however, caring to waste my time in enquiries that can have little interest for the reader. Facts clearly stated are preferable to the dry minutiæ of nomenclature. Let me content myself with giving a brief description of the culprit. She is a Dipteron five millimetres long. [34] Eyes, dark red; face, white. Corselet, ashy 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 the harvest, her legs yellow with pollen, she darts forth and pursues her, keeping behind her in all the turns of her wavering flight. At last, the Hymenopteron 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 front-door, she waits for the Bee to finish her business. The latter reappears at last and, for a few seconds, stands on the threshold of her dwelling, 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 a blow of one of her legs. In vain I peer to discover some sign of apprehension on either side: nothing in the Halictus points to a knowledge of the danger run by her family; nor does anything in the Dipteron betray the dread of a severe correction. Plunderer and plundered stare at each other for a moment; and that is all. If she liked, the genial giantess could rip up with her claw the little bandit that ruins her home; she could crunch her with her mandibles, pink her with her stiletto. She does nothing of the sort, but leaves the brigand in peace, to sit quite close, motionless, with her red eyes fixed on the threshold of the house. Why this fatuous clemency? The Bee departs. 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; she leisurely settles her eggs. No one will disturb her until the Bee’s return. To dust one’s legs with pollen, to distend one’s crop with syrup is a work that takes long a-doing; and the intruder, therefore, has time to spare wherein to commit her felony. Moreover, her chronometer is well-regulated and gives the exact measure of the 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.