So far all would be well, were it not that a grave difficulty arises. However active may be the mother-nurse, it is clear that she cannot meet such a consumption of food. She has to be incessantly on the wing to feed one larva: what must happen if there are a dozen gluttons to provide for? The result of this enormous increase of family can only be want, or even famine, not for the larvæ of the Dipteron (which develop more rapidly than that of the Bembex, profiting by the days when abundance still reigns, their host being yet in early youth), but for the latter, who reaches the moment of metamorphosis without being able to make up for lost time. Besides, when the first guests become pupæ and leave the table free to it, others come, as long as the mother visits the nest, and complete its starvation. In burrows invaded by numerous parasites the Bembex larva is undoubtedly much smaller than one would expect from the heap of food consumed, the remains of which encumber the cell. Limp, emaciated,—only half or a third of its proper size,—it vainly tries to spin a cocoon, the silk for which it has not got, and it perishes in a corner of the cell, amid the pupæ of guests more fortunate than itself. Or its end may be yet more tragic. Should provender fail, or the mother delay too long in returning with food, the Diptera devour it. I ascertained this black deed by bringing up the brood myself. All went well as long as food was plentiful, but if through neglect, or on purpose, the daily supply failed, next day or the day after I was sure to find the Diptera larvæ greedily rending that of the Bembex. Thus, when the nest is invaded by parasites, the legitimate larva is fated to perish either by hunger or a violent death, and this it is which makes the sight of Miltogramma prowling round the nest so odious to the Bembex. The Bembex is not the only victim of these parasites: the burrows of one and all of the mining Hymenoptera are invaded by Tachinids, especially by the Miltogramma. Various observers—notably Lepeletier de Saint Fargeau—have spoken of the manœuvres of these impudent Diptera; but as far as I know none have perceived the very curious case of parasitism at the expense of the Bembex—very curious, because the conditions are quite different. Nests of other Fossors are stored beforehand, and the Miltogramma drops an egg on the prey just as it is being carried in. The provender stored and her egg laid, the Hymenopteron closes up the cell where thenceforward live the legitimate larva and the strangers, unvisited in their prison. Thus, the robbery committed by the parasite is unknown to the mother, and must consequently remain unpunished.