The Volucella, that sanitary inspector of the Vespian city, fulfils a double office: she gives the Wasp’s children a wipe down; and she rids the Wasps’-nest of its dead. For this reason, she is peacefully received, as an assistant, when she enters the burrow to lay her eggs there; for this reason, her grub is tolerated, nay more, respected, in the very heart of the dwelling, where none might stray with impunity. I remember the brutal welcome accorded to the Saperda- and Hylotoma-larvæ when I place them upon a comb. Forthwith grabbed, bruised and riddled with stings, the poor wretches perish. It is quite a different matter with the offspring of the Volucella. They come and go as they please, poke about in the cells, elbow the inhabitants and remain unmolested. Let us give some instances of this clemency, which is very strange in the irascible Wasp. For a couple of hours, I fix my attention on a Volucella-grub established in a cell, side by side with the Wasp-grub, the mistress of the house. The hind-quarters emerge, displaying their papillæ. Sometimes also the pointed fore-part, the head, appears, bending from side to side with sudden, Snake-like motions. The Wasps have just filled their crops at the honey-puddle; they are dispensing the rations, are very busily at work; and these things are taking place in broad daylight, on my table, by the window. As they pass from cell to cell, the nurses repeatedly brush against and stride across the Volucella-grub. There is no doubt that they see it. The intruder does not budge, or, if trodden on, retires inside, only to reappear the next moment. Some of the Wasps stop, bend their heads over the opening, seem to be making enquiries and then go off, without troubling further about the state of things. One of them does something even more remarkable: she tries to give a mouthful to the lawful occupant of the cell; but the larva, which is being squeezed by its visitor, has no appetite and refuses. Without the least sign of anxiety on behalf of the nurseling which she has seen in awkward company, the Wasp retires and goes to distribute her ration elsewhere. In vain I prolong my examination: there is no fluster of any kind. The Volucella-grub is treated as a friend, or at least as a visitor that does not matter. There is no attempt to dislodge it, to worry it, to put it to flight. Nor does the grub seem to trouble greatly about those who come and go. Its tranquillity tells us that it feels at home. Here is some further evidence: the grub has plunged, head downwards, into an empty cell, which is too small to contain the whole of it. Its hind-quarters stick out, very visibly. For long hours it remains motionless in this position. At every moment Wasps pass and repass close by. Three of them, at one time together, at another separately, come and nibble at the edges of the cell; they break off particles which they reduce to paste for a new piece of work.