In the very unlikely supposition that the distribution of the sexes might vary in different parts of the colony, I make a second excavation, at a few yards' distance from the other. It supplies me with another collection both of perfect insects and of pupae and larvae. When the metamorphosis of the laggards is completed, which does not take many days, I proceed to take a general census. It gives me two hundred and fifty Halicti. Well, in this number of Bees, collected in the burrow before any have emerged, I perceive none, absolutely none but females; or, to be mathematically accurate, I find just one male, one alone; and he is so small and feeble that he dies without quite succeeding in divesting himself of his nymphal bands. This solitary male is certainly accidental. A female population of two hundred and forty-nine Halicti implies other males than this abortion, or rather implies none at all. I therefore eliminate him as an accident of no value and conclude that, in the Cylindrical Halictus, the July generation consists of females only. The building-operations start again in the second week of July. The galleries are restored and lengthened; new cells are fashioned and the old ones repaired. Follow the provisioning, the laying of the eggs, the closing of the cells; and, before July is over, there is solitude again. Let me also say that, during the building-period, not a male appears in sight, a fact which adds further proof to that already supplied by my excavations. With the high temperature of this time of the year, the development of the larvae makes rapid progress: a month is sufficient for the various stages of the metamorphosis. On the 24th of August there are once more signs of life above the burrows of the Cylindrical Halictus, but under very different conditions. For the first time, both sexes are present. Males, so easily recognized by their black livery and their slim abdomen adorned with a red ring, hover backwards and forwards, almost level with the ground. They fuss about from burrow to burrow. A few rare females come out for a moment and then go in again. I proceed to make an excavation with my spade; I gather indiscriminately whatever I come across. Larvae are very scarce; pupae abound, as do perfect insects. The list of my captures amounts to eighty males and fifty-eight females. The males, therefore, hitherto impossible to discover, either on the flowers around or in the neighbourhood of the burrows, could be picked up to-day by the hundred, if I wished. They outnumber the females by about four to three; they are also further developed, in accordance with the general rule, for most of the backward pupae give me only females.