Page:Popular Science Monthly Volume 6.djvu/670
THE POPULAR SCIENCE MONTHLY.
as in Nature. The remaining interradials are formed in like manner, their number varying from six to fifteen.
It will be seen that, by first making the double line nearest the base-line, and afterward the others in their order, the spider avails herself of the fact that a less and less distance is to be successively gone over before crossing from one radius to the next; whereas, if she made the shortest double line first, then she would either be liable to entangle the other if she crossed at the, apex, or, if she went around by the base-line, the distances to be gone over would constantly decrease inversely to the lengths of the double lines themselves, causing either waste or entanglement.
It is not yet certain just how long a time is required for making the entire net; but, in one case, the spinning of the five lesser viscid lines occupied the spider ten minutes; the other and longer ones may have taken twice as long; and, as the return-movements are rapidly executed, we may say that, for at least half an hour, the little spider is moving her hinder legs together and with great precision at the rate of 300 times per minute, making the total number of movements 9,000!
How is the Net used?—If the making of the net is peculiar, its use is even more remarkable; and here, fortunately, few points remain to be cleared up; for the spider's response to a disturbance of her net by a fly is so prompt that one may, at any time, witness the operation.
At the close of what to the observer seems a pretty energetic exercise of all her faculties and powers, the spider, without a moment's rest, goes to a point upon the apex-line about an inch from the origin (O), and, firmly grasping the line between the first and second pairs of feet, she walks backward, foot over foot, until her hinder feet are caught in the attachment itself, or in the thickened line near it; in so doing, a certain amount of slack-line has been furled up between the two points held by her hinder legs and the front ones; this slack is kept away from her body by means of the third pair, which are shorter than the others. Evidently the effect of the above operation is to draw the net toward the apex, the two middle radii being most affected, and with them the central portion of the base-line to which they are attached; and the whole net assumes the appearance shown in Fig. 1.
It is now upon the stretch; and the degree of tension is very considerable, judging from the violence of the snap when it is let go; the exact amount has not yet been measured, but, when it is borne in mind that the spider remains motionless for hours, perhaps for days, constantly holding her net ready for action, we may conclude that, as is the case with other insects, her powers and her endurance are, in proportion to her size, quite beyond what we are familiar with among the higher animals. But our spider's ability to keep still is fully