Thus whatever opinion we may hold as to the nature of instinct, the accomplishments and habits of insects are not, properly speaking, connected with the external and visible form of their organs, and their acts do not necessarily presuppose the instruments which would be appropriate to them.
We know that with most organisms, and particularly with plants, an almost imperceptible variation in material circumstances is often enough to modify their character and to produce fresh aptitudes. Nevertheless, we can but wonder, with Fabre, that physical modifications, which, when they do exist, are so slight always as to have escaped the most perfect observation, should have sufficed to determine the appearance of profoundly dissimilar faculties. Inexplicable abilities, unexpected habits, unforeseen physical aptitudes, and unheard-of industries are exercised by means of organs which are here and there practically identical. "The same tools are equally good for any purpose. Talent alone is able to adapt them to manifold ends."
The Anthidia have two particular industries; "those which felt cotton and card the soft down of hairy plants have the same claws, the same mandibles, composed of the same portions as those which knead resin and mix it with fine gravel." [(8/21.)]
The sloe-weevil "bores the hard stone of the sloe with the same rostrum as that which its congeners, so like it in conformation, employ to roll the leaves of the vine and the poplar into tiny cigars."
The implement of the Megachile, the rose-fly, is by no means appropriate to its industry; "yet the perfectly circular fragments of leaves have the precise perfection of form that a punch would give."
The Xylocopa, in order to pierce wood and to bore its galleries in an old rafter, employs "the same utensils which in others are transformed into picks and mattocks to attack clay and gravel, and it is only a predisposition of talent that holds each worker to his speciality."
Moreover, have not the superior animals the same senses and the same structure, yet what inequality there is among them, in the matter of aptitudes and degrees of intelligence!
Habits are no more determined by anatomical peculiarities than are aptitudes or industries.
The two Goat-moth caterpillars, of similar structure, have entirely different stomachic aptitudes; "the exclusive portion of the one is the oak and of the other the hawthorn or the cherry-laurel."
"Whence does the Mantis derive its excessive hunger, its pugnacity, its cannibalism, and the Empusa its sobriety, its peaceableness, when their almost identical organization would seem to indicate an identity of needs, instincts, and habits?"