k, facing the south
to a length of some hundreds of yards and riddled with holes like a
monstrous sponge, is the time-honored dwelling place of the hairy-footed
Anthophora and of her rent free tenant, the three-horned Osmia. Here
also swarm their exterminators: the Sitaris beetle, the parasite of the
Anthophora; the Anthrax fly, the murderer of the Osmia. Ill informed as
to the proper period, I have come rather late, on the 10th of September.
I should have been here a month ago, or even by the end of July, to
watch the fly's operations. My journey threatens to be fruitless: I see
but a few rare Anthrax flies, hovering round the face of the cliff. We
will not despair, however, and we will begin by consulting the locality.

The Anthophora's cells contain this bee in the larval stage. Some of
them provide me with the oil beetle and the Sitaris, rare finds at one
time, today of no use to me. Others contain the Melecta [a parasitic
bee] in the form of a highly colored pupa, or even in that of the full
grown insect. The Osmia, still more precocious, though dating from the
same period, shows herself exclusively in the adult form, a bad omen for
my investigations, for what the Anthrax demands is the larva and not the
perfect insect. The fly's grub doubles my apprehensions. Its development
is complete, the larva on which it feeds is consumed, perhaps several
weeks ago. I no longer doubt but that I have come too late to see what
happens in the Osmia's cocoons.

Is the game lost? Not yet. My notes contain evidence of Anthrax flies
hatching in the latter half of September. Besides, those whom I now see
exploring the rock are not there to take exercise: their preoccupation
is the settling of the family. These belated ones cannot tackle the
Osmia, who, with her firm, adult flesh, would not suit the nursling's
delicate needs and who, moreover, powerful as she is, would offer
resistance. But in autumn a less numerous colony of honey gatherers
takes the place, upon the slope, of the spring colony, from which
it differs in species. In particular, I see the Diadem Anthidium [a
clothier bee who lines her nest with wool and cotton] at work, entering
her galleries at one time with her harvest of pollen dust and at
another with her little bale of cotton. Might not these autumnal Bees be
themselves exploited by the Anthrax, the same that selected the Osmia as
her victim a couple of months earlier? This would explain the presence
of the Anthra