Ephippigers become putrid and the Scoliae die at the same time.

This result is eloquent. Had I left the egg of the Sphex to hatch, the
larva coming out of it would have fed upon the Ephippiger; and for the
hundredth time I should have witnessed an incomprehensible spectacle, that
of an animal which, devoured piecemeal for nearly a fortnight, grows thin
and empty, shrivels up and yet retains to the very end the freshness
peculiar to living flesh. Substitute for this Sphex-larva a Scolia-larva of
almost the same size; let the dish be the same though the guest is
different; and healthy live flesh is promptly replaced by pestilent rotten
flesh. That which under the mandibles of the Sphex would for a long while
have remained wholesome food promptly becomes a poisonous liquescence under
the mandibles of the Scolia.

It is impossible to explain the preservation of the victuals until finally
consumed by supposing that the venom injected by the Wasp when she delivers
her paralysing stings possesses antiseptic properties. The three
Ephippigers were operated on by the Sphex. Able to keep fresh under the
mandibles of the Sphex-larvae, why did they promptly go bad under the
mandibles of the Scolia-larvae? Any idea of an antiseptic must needs be
rejected: a liquid preservative which would act in the first case could not
fail to act in the second, as its virtues would not depend on the teeth of
the consumer.

Those of you who are versed in the knowledge attaching to this problem,
investigate, I beg you, search, sift, see if you can discover the reason
why the victuals keep fresh when consumed by a Sphex, whereas they promptly
become putrid when consumed by a Scolia. For me, I see only one reason; and
I very much doubt whether any one can suggest another.