A superficial operation performed upon the surface of a tender leaf yields them sufficient sustenance.
If the males, the unoccupied males who have leisure to enjoy the pleasures of the palate, ask no more than the sap of the leaf, how should the mothers, busied with the affairs of the breeding-season, find time to waste upon such dearly bought pleasures as the inner juices of the acorn?
No, the acorn is not perforated for the purpose of drinking its juices.

It is possible that once the beak is deeply sunk, the female may take a mouthful or two, but it is certain that food and drink are not the objects in view.
At last I begin to foresee the solution of the problem.

The egg, as I have said, is always at the base of the acorn, in the midst of a soft cottony layer which is moistened by the sap which oozes from the stalk.
The grub, upon hatching out, being as yet incapable of attacking the firm substance of the cotyledons, masticates the delicate felt-like layer at the base of the cup and is nourished by its juices.
But as the acorn matures this layer becomes more solid in its consistency.

The soft tissues harden; the moist tissues dry up.

There is a period during which the acorn fulfils to perfection the conditions most conducive to the welfare of the grub.