The facility with which the worker turns as soon as she reaches the wide tube, her liberty of action, which is now as great as in a doorway communicating with the outer air, might well be misleading and cause the Osmia to treat the narrow passage at the back as though the wide passage in front did not exist.

This would account for the placing of the female in the large tube above the males in the small tube, an arrangement contrary to her custom.
I will not undertake to decide whether the mother really appreciates the danger of my snares, or whether she makes a mistake in considering only the space at her disposal and beginning with males, who are liable to remain imprisoned.

At any rate, I perceive a tendency to deviate as little as possible from the order which safeguards the emergence of both sexes.

This tendency is demonstrated by her repugnance to colonizing my narrow tubes with long series of males.

However, so far as we are concerned, it does not matter much what passes at such times in the Osmia's little brain.