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The most practical system of controlling evaporation is a system of forced ventilation, in which the air is heated around the lamp-flue and passes through the egg-chamber at a rate determined by ventilators in the bottom of the machine. With the outside air cold and dry only slight current is required, but as the outer air becomes warmer or damper more circulation is needed.
At the orifice of the egg-chamber, among the torn fibres of the bark, a little cone-shaped body is visible, with two black eye-spots; in appearance it is precisely like the fore portion of the butter-coloured egg; or, as I have said, like the fore portion of a tiny fish. You would think that an egg had been somehow displaced, had been removed from the bottom of the chamber to its aperture.
Counting ten minutes for each egg-chamber, the full series of forty would represent a period of six or seven hours. The sun will of course move through a considerable distance before the Cigale can finish her work. In such cases the series of apertures follows a spiral curve. The insect turns round the stalk as the sun turns.
Remember the magnificent oval guard-room, running into a vestibule at either end; the egg-chamber slung in the centre and isolated on every side by half a score of pillars; the front-hall expanding into a wide mouth and surmounted by a network of taut threads forming a trap. The semi-transparency of the walls allows us to see the Spider engaged in her household affairs.
There are certain cast-off articles of clothing, certain rags and tatters, left on the threshold of the egg-chamber by the new-born grubs as they leave it and hurry in search of a new lodging. We shall see in a moment what these vestiges mean. But in spite of my visits, which were so assiduous as to deserve success, I had never contrived to see the young Cigales emerge from their egg-chambers.
The egg-chamber closes of its own accord as the woody fibres which have been displaced return to their position, and the Cigale climbs a little higher, moving upwards in a straight line, by about the length of its ovipositor. It then makes another puncture and a fresh chamber for another ten or twelve eggs. In this way it scales the twig from bottom to top.
The insect is motionless, and hardly ten minutes elapse between the first cut of the ovipositor and the filling of the egg-chamber with eggs. The ovipositor is then withdrawn with methodical deliberation, in order that it may not be strained or bent.
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