It is a treat to the eyes to see it revolve.
What is the object of this circular motion?
It is this: the brief contact of the spinnerets has given a starting-point for a thread, which the Spider must now draw from her silk warehouse and gradually roll around the captive, so as to swathe him in a winding-sheet which will overpower any effort made.

It is the exact process employed in our wire-mills: a motor-driven spool revolves and, by its action, draws the wire through the narrow eyelet of a steel plate, making it of the fineness required, and, with the same movement, winds it round and round its collar.
Even so with the Epeira's work.

The Spider's front tarsi are the motor; the revolving spool is the captured insect; the steel eyelet is the aperture of the spinnerets.

To bind the subject with precision and dispatch nothing could be better than this inexpensive and highly effective method.
Less frequently, a second process is employed.

With a quick movement, the Spider herself turns round about the motionless insect, crossing the web first at the top and then at the bottom and gradually placing the fastenings of her line.