Though the males do not come to visit the environs of the burrows, they might be elsewhere, particularly on the flowers where the females go plundering. I did not fail to explore the fields, insect-net in hand. My search was invariably fruitless. On the other hand, those males, now nowhere to be found, are plentiful later, in September, along the borders of the paths, on the close-set flowers of the eringo. This singular colony, reduced exclusively to mothers, made me suspect the existence of several generations a year, whereof one at least must possess the other sex. I continued therefore, when the building-who was over, to keep a daily watch on the establishment of the Cylindrical Halictus, in order to seize the favourable moment that would verify my suspicions. For six weeks, solitude reigned above the burrows: not a single Halictus appeared; and the path, trodden by the wayfarers, lost its little heaps of rubbish, the only signs of the excavations. There was nothing outside to show that the warmth down below was hatching populous swarms. July comes and already a few little mounds of fresh earth betoken work going on underground in preparation for an exodus in the near future. As the males, among the Hymenoptera, are generally further advanced than the females and quit their natal cells earlier, it was important that I should witness the first exits made, so as to dispel the least shadow of a doubt. A violent exhumation would have a great advantage over the natural exit: it would place the population of the burrows immediately under my eyes, before the departure of either sex. In this way, nothing could escape from me and I was dispensed from a watch which, for all its attentiveness, was not to be relied upon absolutely. I therefore resolve upon a reconnaissance with the spade. I dig down to the full depth of the galleries and remove large lumps of earth which I take in my hands and break very carefully so as to examine all the parts that may contain cells. Halicti in the perfect state predominate, most of them still lodged in their unbroken chambers. Though they are not quite so numerous, there are also plenty of pupae. I collect them of every shade of colour, from dead-white, the sign of a recent transformation, to smoky-brown, the mark of an approaching metamorphosis. Larvae, in small quantities, complete the harvest. They are in the state of torpor that precedes the appearance of the pupa. I prepare boxes with a bed of fresh, sifted earth to receive the larvae and the pupae, which I lodge each in a sort of half-cell formed by the imprint of my finger. I will await the transformation to decide to which sex they belong. As for the perfect insects, they are inspected, counted and at once released.