e Anthophorae, I must not omit to mention one very
remarkable peculiarity. All the Bees invaded by these grubs that have
hitherto been observed have, without one exception, been male
Anthophorae. Those whom I drew from their lurking-places were males;
those whom I caught upon the flowers were males; and, in spite of the
most active search, I failed to find a single female at liberty. The
cause of this total absence of females is easy to understand.

If we remove a few clods from the area occupied by the nests, we see
that, though all the males have already opened and abandoned their
cells, the females, on the contrary, are still enclosed in theirs, but
on the point of soon taking flight. This appearance of the males
almost a month before the emergence of the females is not peculiar to
the Anthophorae; I have observed it in many other Bees and
particularly in the Three-horned Osmia (_O. tricornis_), who inhabits
the same site as the Hairy-footed Anthophora (_A. pilipes_). The males
of the Osmia make their appearance even before those of the Anthophora
and at so early a season that the young Sitaris-larvae are perhaps not
yet aroused by the instinctive impulse which urges them to activity.
It is no doubt to their precocious awakening that the males of the
Osmia owe their ability to traverse with impunity the corridors in
which the young Sitaris-grubs are heaped together, without having the
latter fasten to their fleece; at least, I cannot otherwise explain
the absence of these larvae from the backs of the male Osmiae, since,
when we place them artificially in the presence of these Bees, they
fasten on them as readily as on the Anthophorae.

The emergence from the common site begun by the male Osmiae is
continued by the male Anthophorae and ends with the almost
simultaneous emergence of the female Osmiae and Anthophorae. I was
easily able to verify this sequence by observing at my own place, in
the early spring, the dates at which the cells, collected during the
previous autumn, were broken.

At the moment of their emergence, the male Anthophorae, passing
through the galleries in which the Sitaris-larvae are waiting on the
alert, must pick up a certain number of them; and those among them
who, by entering empty corridors, escape the enemy on this first
occasion will not evade him for long, for the rain, the chilly air and
the darkness bring them back to their former homes, where they take
shelter now in one gallery, now