Whether for lack of sufficient room, or for other reasons which escape me, the larva of the Sisyphus, having employed a certain amount in the smoothing of the interior, ejects the rest of its digestive products from its dwelling.
Let us examine one of these "pears" when the inmate is already partly grown.

Sooner or later we shall see a spot of moisture appear at some point on the surface; the wall softens, becomes thinner, and then, through the softened shell, a jet of dark green excreta rises and falls back upon itself in corkscrew convolutions.

One excrescence the more has been formed; as it dries it becomes black.
What has occurred?
The larva has opened a temporary breach in the wall of its shell; and through this orifice, in which a slight thickness of the outer glaze still remains, it has expelled the excess of mortar which it could not employ within.

This practice of forming oubliettes in the shell of its prison does not endanger the grub, as they are immediately closed, and hermetically sealed by the base of the jet, which is compressed as by a stroke of a trowel.

The stopper is so quickly put in place that the contents remain moist in spite of the frequent breaches made in the shell of the "pear." There is no danger of an influx of the dry outer air.
The Sisyphus seems to be aware of the peril which later on, in the dog-days, will threaten its "pear," small as it is, and so near the surface of the ground.