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The two species adopted are Solenius vagus, which quits the bramble at the end of June, and Osmia detrita, which comes a little earlier, in the first fortnight of the same month. I therefore alternate Osmia-cocoons and Solenius-cocoons, with the latter at the top of the series, either in glass tubes or between two bramble-troughs joined into a cylinder. The result of this promiscuity is striking.

Here, instead of the lack of order in the distribution of the sexes which we find with O. tridentata, we have an order remarkable for consistency and simplicity. I have before me the list of the series of O. detrita collected last winter. Here are some of them: 1. A series of twelve: seven females, beginning with the bottom of the tunnel, and then five males.

Ab opposito autem praedicti fontis natatorij habetur imago lapidea, rudi et vetusto opere sculpta, deformiterque detrita, quae manus Absalon nuncupatur, cuius ratio lib. 2. Regum monstratur.

Even if these interpretations should be open to doubt, one result at least is certain: with O. detrita, the laying is divided into two groups, with no intermingling of the sexes; the first group laid yields nothing but females, the second, or more recent, yields nothing but males.

The brambles, in my district, harbour two other Osmiae, both of much smaller size: O. detrita, PEREZ, and O. parvula, DUF. The first is very common, the second very rare; and until now I have found only one of her nests, placed above a nest of O. detrita, in the same bramble.