portation of the
geranium. Where again did the Silvery Megachile, for whom I created an
exotic shrubbery, make the acquaintance of the lopezia, which comes from
Mexico? She certainly is making a first start. Never did her village or
mine possess a stalk of that chilly denizen of our hot-houses. She is
making a first start; and behold her straightway a graduate, versed in
the art of carving unfamiliar foliage.

People often talk of the long apprenticeships served by instinct, of its
gradual acquirements, of its talents, the laborious work of the ages.
The Megachiles affirm the exact opposite. They tell me that the animal,
though invariable in the essence of its art, is capable of innovation
in the details; but at the same time they assure me that any such
innovation is sudden and not gradual. Nothing prepares the innovations,
nothing improves them or hands them down; otherwise a selection would
long ago have been made amid the diversity of foliage; and the
shrub recognized as the most serviceable, especially when it is also
plentiful, would alone supply all the building-materials needed. If
heredity transmitted industrial discoveries, a Megachile who thought of
cutting her disks out of pomegranate-leaves and found them satisfactory
ought to have instilled a liking for similar materials into her
descendants; and we should this day find Leaf-cutters faithful to the
pomegranate-leaves, workers who remained exclusive in their choice of
the raw material. The facts refute these theories.

People also say:

'Grant us a variation, however small, in the insect's industry; and
that variation, accentuated more and more, will produce a new race and
finally a fixed species.'

This trifling variation is the fulcrum for which Archimedes clamoured in
order to lift the world with his system of levers. The Megachiles
offer us one and a very great one: the indefinite variation of their
materials. What will the theorists' levers lift with this fulcrum? Why,
nothing at all! Whether they cut the delicate petals of the geranium or
the tough leaves of the lilac-bushes, the Leaf-cutters are and will
be what they were. This is what we learn from the persistence of each
species in its structural details, despite the great variety of the
foliage employed.

CHAPTER 9. THE COTTON-BEES.

The evidence of the Leaf-cutters proves that a certain latitude is
left to the insect in its choice of materials for the nest; and this is
confirmed by