A couple of Osmiae, more forward than the others, set to work on the 23rd of April.
Both of them started their laying by placing males in the narrow tubes.
The meagre supply of provisions was enough in itself to show the sex, which proved later to be in accordance with my anticipations.

We see then that, by my artifices, the whole swarm starts with the converse of the normal order.

This inversion is continued, at no matter what period, from the beginning to the end of the operations.

The series which, according to rule, would begin with females now begins with males.

Once the larger gallery is reached, the laying is pursued in the usual order.
We have advanced one step and that no small one: we have seen that the Osmia, when circumstances require it, is capable of reversing the sequence of the sexes.