The door can no longer be closed; and the assailant is henceforth master of the fortress.

Our first impression is that the muscle moving the lid has been cut with a quick-acting pair of shears.

This idea must be dismissed.

The Drilus is not well enough equipped with jaws to gnaw through a fleshy mass so promptly.

The operation has to succeed at once, at the first touch: if not, the animal attacked would retreat, still in full vigour, and the siege must be recommenced, as arduous as ever, exposing the insect to fasts indefinitely prolonged.