arance. To
penetrate it, she would have to become an excavating tool once more and
resume the cast-off rags which she left behind in the exit window; she
would have to retrace her steps, to be reborn a pupa; and life knows
none of these retrogressions. The full grown insect, if endowed with
claws, mandibles and plenty of perseverance, might at a pinch force the
mortar casket; but the fly is not so endowed. Her slender legs would be
strained and deformed by merely sweeping away a little dust; her mouth
is a sucker for gathering the sugary exudations of the flowers and not
the solid pincers needed for the crumbling of cement. There is no auger
either, no bore copied from that of the Leucospis, no implement of any
kind that can work its way into the thickness of the wall and dispatch
the egg to its destination. In short, the mother is absolutely incapable
of settling her eggs in the chamber of the Mason bee.

Can it be the grub that makes its own way into the storeroom, that same
grub which we have seen draining the Chalicodoma with its leech-like
kisses? Let us call the creature to mind: a little oily sausage, which
stretches and curls up just where it lies, without being able to shift
its position. Its body is a smooth cylinder; its mouth simply a
circular lip. Not one ambulatory organ does it possess; not even hairs,
protuberances or wrinkles to enable it to crawl. The animal is made
for digestion and immobility. Its organization is incompatible with
movement; everything tells us so in the clearest fashion. No, this
grub is even less able than the mother to make its way unaided into the
mason's dwelling. And yet the provisions are there; those provisions
must be reached: it is a matter of life or death; to be or not to be.
Then how does the fly set about it? It would be vain for me to question
probabilities, too often illusory; to obtain a reply of any value, I
have but one resource; I must attempt the nearly impossible and watch
the Anthrax from the egg onwards.

Although Anthrax flies are fairly common, in the sense of there being
several different species, they are not plentiful when it is a case of
wanting a colony populous enough to admit of continuous observation.
I see them, now here, now there, in the fiercely sun-scorched places,
flitting hither and thither on the old walls, the slopes and the sand,
sometimes in small platoons, most often singly. I can expect nothing
of those vagabonds, who are here today and