s and males only,
but in short series, between one and five. The mother is here so much
hampered in her work that they are rarely occupied from end to end; the
Osmia seems in a hurry to leave them and to go and colonize the front
tube, whose ample space will leave her the liberty of movement necessary
for her operations. The other rear tubes, the minority, whose diameter
is about 6 millimetres (.234 inch.--Translator's Note.), contain
sometimes only females and sometimes females at the back and males
towards the opening. One can see that a tube a trifle wider and a mother
slightly smaller would account for this difference in the results.
Nevertheless, as the necessary space for a female is barely provided
in this case, we see that the mother avoids as far as she can a two-sex
arrangement beginning with males and that she adopts it only in the
last extremity. Finally, whatever the contents of the small tube may
be, those of the large one, following upon it, never vary and consist of
females at the back and males in front.

Though incomplete, because of circumstances very difficult to control,
the result of the experiment is none the less very striking. Twenty-five
apparatus contain only males in their narrow gallery, in numbers varying
from a minimum of one to a maximum of five. After these comes the colony
of the large gallery, beginning with females and ending with males. And
the layings in these apparatus do not always belong to late summer or
even to the intermediate period: a few small tubes contain the earliest
eggs of the Osmiae. 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. Would it be possible, provided that the tube were
long enough, to obtain a complete inv