n individuals; and there are six females at
least to one male. This disparity is maintained, in more or less marked
proportions, whatever the species of the bee invaded. In the cocoons of
the Mason bee of the Sheds, I discover the average proportion to be six
females to one male; in those of the Mason bee of the Walls, I find one
male to fifteen females.

These facts, which I am unable to state with any greater precision, are
enough to give rise to the suspicion that the males, who are even tinier
dwarfs than the females and who, moreover, like all insects, are injured
by a single act of pairing, must, in most cases, remain strangers to
the females. Can the mothers, in fact, dispense with their assistance,
without being deprived of offspring on that account? I do not say yes,
but I do not say no. The duality of the sexes is a hard problem. Why
two sexes? Why not just one? It would have been much simpler and saved
a great deal of foolery. Why such a thing as sex, when the tuber of the
Jerusalem artichoke can do without it? These are the pregnant questions
suggested to me, in the end, by Monodontomerus cupreus, the insect so
infinitesimal in body and so overpowering in name that I had really
vowed never to speak of it again by its official designation.

CHAPTER IV. LARVAL DIMORPHISM

If the reader has paid any attention to the story of the Anthrax, he
must have perceived that my narrative is incomplete. The fox in the
fable saw how the lion's visitors entered his den, but did not see how
they went out. With us, it is the converse: we know the way out of the
mason bee's fortress, but we do not know the way in. To leave the cell
of which he has eaten the owner, the Anthrax becomes a perforating
machine, a living tool from which our own industry might take a hint if
it required new drills for boring rocks. When the exit tunnel is opened,
this tool splits like a pod bursting in the sun; and from the stout
framework there escapes a dainty fly, a velvety flake, a soft fluff that
astounds us by its contrast with the roughness of the depths whence it
ascends. On this point, we know pretty well what there is to know. There
remains the entrance into the cell, a puzzle that has kept me on the
alert for a quarter of a century.

To begin with, it is evident that the mother cannot lodge her egg in the
cell of the mason bee, which has been long closed and barricaded with
a cement wall by the time that the Anthrax makes her appe