That idea we must abandon at once; the passage is extremely narrow and encumbered with shavings, so that such a thing would be impossible.  Moreover, according to the direction of the stem, accordingly as it pointed upwards or downwards, the egg would have to fall downwards in one acorn and upwards in another.

A second explanation suggests itself, not less perilous.  It might be said:  “The cuckoo lays her egg on the grass, no matter where; she lifts it in her beak and places it in the nearest appropriate nest.”  Might not the Balaninus follow an analogous method?  Does she employ the rostrum to place the egg in its position at the base of the acorn?  I cannot see that the insect has any other implement capable of reaching this remote hiding-place.

Nevertheless, we must hastily reject such an absurd explanation as a last, desperate resort.  The elephant-beetle certainly does not lay its egg in the open and seize it in its beak.  If it did so the delicate ovum would certainly be destroyed, crushed in the attempt to thrust it down a narrow passage half choked with debris.

This is very perplexing.  My embarrassment will be shared by all readers who are acquainted with the structure of the elephant-beetle.  The grasshopper has a sabre, an oviscapt which plunges into the earth and sows the eggs at the desired depth; the Leuscopis has a probe which finds its way through the masonry of the mason-bee and lays the egg in the cocoon of the great somnolent larva; but the Balaninus has none of these swords, daggers, or pikes; she has nothing but the tip of her abdomen.  Yet she has only to apply that abdominal extremity to the opening of the passage, and the egg is immediately lodged at the very bottom.

Anatomy will give us the answer to the riddle, which is otherwise indecipherable.  I open the body of a gravid female.  There, before my eyes, is something that takes my breath away.  There, occupying the whole length of the body, is an extraordinary device; a red, horny, rigid rod; I had almost said a rostrum, so greatly does it resemble the implement which the insect carries on his head.  It is a tube, fine as a horsehair, slightly enlarged at the free extremity, like an old-fashioned blunderbuss, and expanding to form an egg-shaped capsule at the point of origin.

This is the oviduct, and its dimensions are the same as those of the rostrum.  As far as the perforating beak can plunge, so far the oviscapt, the interior rostrum, will reach.  When working upon her acorn the female chooses the point of attack so that the two complementary instruments can each of them reach the desired point at the base of the acorn.

The matter now explains itself.  The work of drilling completed, the gallery ready, the mother turns and places the tip of the abdomen against the orifice.  She extrudes the internal mechanism, which easily passes through the loose debris of the boring.  No sign of the probe appears, so quickly and discreetly does it work; nor is any trace of it to be seen when, the egg having been properly deposited, the implement ascends and returns to the abdomen.  It is over, and the mother departs, and we have not caught a glimpse of her internal mechanism.