A similar state of affairs is visible in front of the neck, and probably under the entire surface of the yielding carapace.

The fineness of the membrane at the articulations enables us to perceive it at these unarmoured points, but the cuirass of the corselet conceals it in the central portion.
At these points the circulatory reserves of the insect are pulsing in tidal onsets.

Their gradual increase is betrayed by pulsations like those of a hydraulic ram.

Distended by this rush of humours, by this injection in which the organism concentrates all its forces, the outer skin finally splits along the line of least resistance which the subtle previsions of life have prepared.

The fissure extends the whole length of the corselet, opening precisely along the ridge of the keel, as though the two symmetrical halves had been soldered together.
Unbreakable elsewhere, the envelope has yielded at this median point, which had remained weaker than the rest of the sheath.