belly uppermost and the young Scolia on top. I might utilise the
subjects of my previous experiments; but, as I have to take precautions
against the disturbance which may have been caused by the test already
undergone, I prefer to operate on new patients, a luxury in which the
richness of my menagerie allows me to indulge. I move the Scolia from
its position, extract its head from the entrails of the Cetonia-larva
and leave it to its own resources on its victim's belly. Betraying every
symptom of uneasiness, the grub gropes, hesitates, casts about and does
not insert its mandibles anywhere, though it is now the ventral surface
which it is exploring. It would not display greater hesitation if placed
on the back of the larva. I repeat, who knows? On this side it might
perhaps injure the nervous plexus, which is even more essential than the
dorsal vessel. The inexperienced grub must not drive in its mandibles at
random; its future is jeopardized if it gives a single ill-judged bite.
If it gnaws at the spot where I myself operated with my needle wrought
into a scalpel, its victuals will very soon turn putrid. Once more,
then, we witness an absolute refusal to perforate the skin of the victim
elsewhere than at the very point where the egg was fixed.

The mother selects this point, which is undoubtedly that most favourable
to the future prosperity of the larva, though I am not able clearly to
discern the reasons for her choice; she fixes the egg to it; and the
place where the opening is to be made is henceforth determined. It is
here that the grub must bite: only here, never elsewhere. Its invincible
refusal to tackle the Cetonia in any other part, even though it should
die of starvation, shews us how rigorous is the rule of conduct with
which its instinct is inspired.

As it gropes about, the grub laid on the victim's ventral surface sooner
or later rediscovers the gaping wound from which I have removed it. If
this takes too long for my patience, I can myself guide its head to the
place with the point of a paint-brush. The grub then recognizes the hole
of its own making, slips its neck into it and little by little dives
into the Cetonia's belly, so that the original state of affairs appears
to be exactly restored. And yet its successful rearing is henceforth
highly problematical. It is possible that the larva will prosper,
complete its development and spin its cocoon; it is also possible--and
the case is not unusual--that