To this rule I have not yet found an exception, at least in galleries of normal diameter.

In each new abode the mother busies herself first of all with the more important sex.

Bearing this point in mind, would it be possible for me, by manoeuvring, to obtain an inversion of this order and make the laying begin with males?
I think so, from the results already ascertained and the irresistible conclusions to be drawn from them.

The double-galleried tubes are installed in order to put my conjectures to the proof.
The back gallery, 5 or 6 millimetres wide (.195 to .234 inch .-- Translator's Note.), is too narrow to serve as a lodging for normally developed females.

If, therefore, the Osmia, who is very economical of her space, wishes to occupy them, she will be obliged to establish males there.