On this occasion all goes well, but so slowly that the descent of the drill, even when amplified by the magnifying-glass, cannot be perceived.  The insect veers round perpetually, rests, and resumes her work.  An hour passes, two hours, wearying the observer by their sustained attention; for I wish to witness the precise moment when the beetle withdraws her drill, turns round, and deposits her egg in the mouth of the orifice.  This, at least, is how I foresee the event.

Two hours go by, exhausting my patience.  I call the household to my aid.  Three of us take turns, keeping an uninterrupted watch upon the persevering creature whose secret I intend at any cost to discover.

[Illustration:  1.  THE GREY LOCUST.

1’.  THE NERVATURES OF THE WING.

2.  THE BALANINUS FALLEN A VICTIM TO THE LENGTH OF HER PROBOSCIS.]

It was well that I called in helpers to lend me their eyes and their attention.  After eight hours—­eight interminable hours, when it was nearly night, the sentinel on the watch calls me.  The insect appears to have finished.  She does, in fact, very cautiously withdraw her beak, as though fearing to slip.  Once the tool is withdrawn she holds it pointing directly in front of her.

The moment has come....  Alas, no!  Once more I am cheated; my eight hours of observation have been fruitless.  The Balaninus decamps; abandons her acorn without laying her eggs.  I was certainly right to distrust the result of observation in the open woods.  Such concentration among the oaks, exposed to the sun, wind, and rain would have been an intolerable task.

During the whole of October, with the aid of such helpers as are needed, I remark a number of borings, not followed by the laying of eggs.  The duration of the observer’s task varies greatly.  It usually amounts to a couple of hours; sometimes it exceeds half the day.

With what object are these perforations made, so laborious and yet so often unused?  Let us first of all discover the position of the egg, and the first mouthfuls taken by the grub, and perhaps the reply will be found.

The peopled acorns remain on the oak, held in their cups as though nothing had occurred to the detriment of the cotyledons.  With a little attention they may be readily recognised.  Not far from the cup, on the smooth, still green envelope of the acorn a little point is visible; a tiny needle-prick.  A narrow brown aureole, the product of mortification, is not long in appearing.  This marks the opening of the hole.  Sometimes, but more rarely, the hole is drilled through the cup itself.

Let us select those acorns which have been recently perforated:  that is to say, those in which the perforation is not yet surrounded by the brown ring which appears in course of time.  Let us shell them.  Many contain nothing out of the way; the Balaninus has bored them but has not laid her eggs in them.  They resemble the acorns which for hours and hours were drilled in my laboratory but not utilised.  Many, on the contrary, contain an egg.