Free of impediment, the line runs straight from the centre of the net to the ambush-tent.

Its length averages twenty-two inches.

The Angular Epeira, settled high up in the trees, has shown me some as long as eight or nine feet.
There is no doubt that this slanting line is a foot-bridge which allows the Spider to repair hurriedly to the web, when summoned by urgent business, and then, when her round is finished, to return to her hut.
In fact, it is the road which I see her follow, in going and coming.
But is that all?
No; for, if the Epeira had no aim in view but a means of rapid transit between her tent and the net, the foot-bridge would be fastened to the upper edge of the web.

The journey would be shorter and the slope less steep.
Why, moreover, does this line always start in the centre of the sticky network and nowhere else?
Because that is the point where the spokes meet and, therefore, the common centre of vibration.

Anything that moves upon the web sets it shaking.