her leaves; the second
her wadding; the third her resin. None of these guilds has ever changed
trades with another; and none ever will. There you have instinct,
keeping the workers to their specialities. There are no innovations
in their workshops, no recipes resulting from experiment, no ingenious
devices, no progress from indifferent to good, from good to excellent.
To-day's method is the facsimile of yesterday's; and to-morrow will know
no other.

But, though the manufacturing-process is invariable, the raw material is
subject to change. The plant that supplies the cotton differs in species
according to the locality; the bush out of whose leaves the pieces will
be cut is not the same in the various fields of operation; the tree that
provides the resinous putty may be a pine, a cypress, a juniper, a
cedar or a spruce, all very different in appearance. What will guide the
insect in its gleaning? Discernment.

These, I think, are sufficient details of the fundamental distinction
to be drawn in the insect's mentality; the distinction, that is, between
instinct and discernment. If people confuse these two provinces, as they
nearly always do, any understanding becomes impossible; the last glimmer
of light disappears behind the clouds of interminable discussions. From
an industrial point of view, let us look upon the insect as a worker
thoroughly versed from birth in a craft whose essential principles never
vary; let us grant that unconscious worker a gleam of intelligence
which will permit it to extricate itself from the inevitable conflict of
attendant circumstances; and I think that we shall have come as near to
the truth as the state of our knowledge will allow for the moment.

Having thus assigned a due share both to instinct and the aberrations
of instinct when the course of its different phases is disturbed, let
us see what discernment is able to do in the selection of a site for
the nest and materials for building it; and, leaving the Pelopaeus, upon
whom it is useless to dwell any longer, let us consider other examples,
picked from among those richest in variations.

The Mason-bee of the Sheds (Chalicodoma rufitarsis, PEREZ) well deserves
the name which I have felt justified in giving her from her habits: she
settles in numerous colonies in our sheds, on the lower surface of the
tiles, where she builds huge nests which endanger the solidity of the
roof. Nowhere does the insect display a greater zeal for work th