The subterranean climate varies too little, changes too slowly, and would not afford it the precise information required for the most important action of its life--the escape into the sunshine at the time of metamorphosis.
Patiently, for weeks, perhaps for months, it digs, clears, and strengthens a vertical shaft, leaving only a layer of earth a finger's breadth in thickness to isolate it from the outer world.

At the bottom it prepares a carefully built recess.

This is its refuge, its place of waiting, where it reposes in peace if its observations decide it to postpone its final departure.

At the least sign of fine weather it climbs to the top of its burrow, sounds the outer world through the thin layer of earth which covers the shaft, and informs itself of the temperature and humidity of the outer air.
If things are not going well--if there are threats of a flood or the dreaded _bise_--events of mortal gravity when the delicate insect issues from its cerements--the prudent creature re-descends to the bottom of its burrow for a longer wait.

If, on the contrary, the state of the atmosphere is favourable, the roof is broken through by a few strokes of its claws, and the larva emerges from its tunnel.
Everything seems to prove that the burrow of the Cigale is a waiting-room, a meteorological station, in which the larva makes a prolonged stay; sometimes hoisting itself to the neighbourhood of the surface in order to ascertain the external climate; sometimes retiring to the depths the better to shelter itself.