self more readily to laboratory experiments, both because she
is stronger and because the same stalk will contain a goodly number of
her cells. The first fact to be ascertained is the order of hatching.
I take a glass tube, closed at one end, open at the other and of a
diameter similar to that of the Osmia's tunnel. In this I place, one
above the other, exactly in their natural order, the ten cocoons, or
thereabouts, which I extract from a stump of bramble. The operation is
performed in winter. The larvae, at that time, have long been enveloped
in their silken case. To separate the cocoons from one another, I employ
artificial partitions consisting of little round disks of sorghum, or
Indian millet, about half a centimetre thick. (About one-fifth of an
inch.--Translator's Note.) This is a white pith, divested of its fibrous
wrapper and easy for the Osmia's mandibles to attack. My diaphragms are
much thicker than the natural partitions; this is an advantage, as we
shall see. In any case, I could not well use thinner ones, for these
disks must be able to withstand the pressure of the rammer which places
them in position in the tube. On the other hand, the experiment showed
me that the Osmia makes short work of the material when it is a case of
drilling a hole through it.

To keep out the light, which would disturb my insects destined to spend
their larval life in complete darkness, I cover the tube with a thick
paper sheath, easy to remove and replace when the time comes for
observation. Lastly, the tubes thus prepared and containing either
Osmiae or other bramble-dwellers are hung vertically, with the opening
at the top, in a snug corner of my study. Each of these appliances
fulfils the natural conditions pretty satisfactorily: the cocoons from
the same bramble-stick are stacked in the same order which they occupied
in the native shaft, the oldest at the bottom of the tube and the
youngest close to the orifice; they are isolated by means of partitions;
they are placed vertically, head upwards; moreover, my device has
the advantage of substituting for the opaque wall of the bramble a
transparent wall which will enable me to follow the hatching day by day,
at any moment which I think opportune.

The male Osmia splits his cocoon at the end of June and the female at
the beginning of July. When this time comes, we must redouble our watch
and inspect the tubes several times a day if we would obtain exact
statistics of the bir