Having said this, let us experiment a little. In the web of the House Spider, I make a round hole, two fingers wide. The hole remains yawning all day long; but next morning it is invariably closed. An extremely thin gauze covers the breach, the dark appearance of which contrasts with the dense whiteness of the surrounding fabric. The gauze is so delicate that, to make sure of its presence, I use a straw rather than my eyes. The movement of the web, when this part is touched, proves the presence of an obstacle. Here, the matter would appear obvious. The House Spider has mended her work during the night; she has put a patch in the torn stuff, a talent unknown to the Garden Spiders. It would be greatly to her credit, if a mere attentive study did not lead to another conclusion. The web of the House Spider is, as we were saying, a platform for watching and exploring; it is also a sheet into which the insects caught in the overhead rigging fall. This surface, a domain subject to unlimited shocks, is never strong enough, especially as it is exposed to the additional burden of little bits of plaster loosened from the wall. The owner is constantly working at it; she adds a new layer nightly. Every time that she issues from her tubular retreat or returns to it, she fixes the thread that hangs behind her upon the road covered. As evidence of this work, we have the direction of the surface-lines, all of which, whether straight or winding, according to the fancies that guide the Spider's path, converge upon the entrance of the tube. Each step taken, beyond a doubt, adds a filament to the web. We have here the story of the Processionary of the Pine, {30} whose habits I have related elsewhere. When the caterpillars leave the silk pouch, to go and browse at night, and also when they enter it again, they never fail to spin a little on the surface of their nest. Each expedition adds to the thickness of the wall. When moving this way or that upon the purse which I have split from top to bottom with my scissors, the Processionaries upholster the breach even as they upholster the untouched part, without paying more attention to it than to the rest of the wall. Caring nothing about the accident, they behave in the same way as on a non-gutted dwelling. The crevice is closed, in course of time, not intentionally, but solely by the action of the usual spinning. We arrive at the same conclusion on the subject of the House Spider. Walking about her platform every night, she lays fresh courses without drawing a distinction between the solid and the hollow. She has not deliberately put a patch in the torn texture; she has simply gone on with her ordinary business. If it happen that the hole is eventually closed, this fortunate result is the outcome not of a special purpose, but of an unvarying method of work.