issue from the cocoon a little earlier than the females. In the case
of the Three-pronged Osmia, the male has about a week's start.
Consequently, in a populous gallery, there is always a certain number
of males, who are hatched seven or eight days before the females and
who are distributed here and there over the series. This would be
enough to make any regular hatching-sequence impossible in either
direction.

These surmises accord with the facts: the chronological sequence of
the cells tells us nothing about the chronological sequence of the
hatchings, which take place without any definite order. There is,
therefore, no surrender of rights of primogeniture, as Leon Dufour
thought: each insect, regardless of the others, bursts its cocoon
when its time comes; and this time is determined by causes which
escape our notice and which, no doubt, depend upon the potentialities
of the egg itself. It is the case with the other bramble-dwellers
which I have subjected to the same test (Osmia detrita, Anthidium
scapulare, Solenius vagus, etc.); and it must also be the case with
Odynerus rubicola: so the most striking analogies inform us.
Therefore the singular exception which made such an impression on
Dufour's mind is a sheer logical illusion.

An error removed is tantamount to a truth gained; and yet, if it were
to end here, the result of my experiment would possess but slight
value. After destruction, let us turn to construction; and perhaps we
shall find the wherewithal to compensate us for an illusion lost. Let
us begin by watching the exit.

The first Osmia to leave her cocoon, no matter what place she
occupies in the series, forthwith attacks the ceiling separating her