How does a spider construct its web?

Building a spider web is a very complex process. Referring to the stages below, first the spider (at point A) dangles a length of sticky silk, which can be carried in the air until it sticks to an anchor point, such as a branch (see point B). Once the silk is attached to point B, the spider pulls it taut and fixes the original end to anchor point A, creating the ‘bridge thread’ (red).
Now the spider fixes a second strand (blue) to point A and spins this while crossing the bridge. This thread is looser than the first and droops below the bridge thread. At point B the spider attaches this strand but doesn’t pull it taut.
Next the spider travels back halfway along the now anchored loose thread (to point C; the web centre); the weight of the spider bows the thread into a V-shape, and from the bottom of the ‘V’, the spider attaches a third thread, which is spun as the arachnid descends to another branch (anchor point D). This turns the V-shape into a Y-shape, and creates another integral pathway. The spider continues to create more of these structural strands until a basic framework is in place.
With the main frame lines in position, the spider adds radial threads from the centre to surrounding vegetation, much like the spokes of a wheel. These form the non-stick paths upon which the creature can safely navigate its trap.
Next the spider creates a silk spiral across the radial lines from the inside out. Using this as a template, it repeats this stage, except this time the threads are coated in bug-catching adhesive.
Now all the spider needs to do is position itself at the centre of its trap and wait. These creatures are very sensitive to vibrations and, quick as a flash, the spider can expertly traverse its web to confront a haplessly entangled victim.