Spiders have several spinnerets at the base of their abdomen. Every
gland produces a thread for a special purpose. There are seven
different known glands. Each spider possesses only some of these
glands and not all seven together.
Normally a spider has three pairs of spinnerets, but
there are spiders with just one pair or as many as
four pairs of spinnerets, with each spinneret having
its own function.
To create the initial base line, the spider uses
the wind to carry its initial sticky thread. The
silk is released from its spinnerets and carried by
the wind to a suitable surface. When it sticks to a
surface the spider will carefully walk over the
thread and strengthen it with a second thread. This
process is repeated until the primary thread is
strong enough to support the rest of the netting.
After strengthening the first thread, the spider
will continue to make a Y shaped netting. The first
three radials of the web are now constructed. More
radials are added making sure that the distance
between each radial is small enough to cross. This
means that the number of radials in a web directly
depends on the size of the spider plus the size of
the web.
After the radials are complete the spider will strengthen the centre of the web with about five circular threads.
Then a spiral of non-sticky, evenly spaced, circular threads are made for the spider to easily move around its own web during construction. Then, beginning from the outside in, the spider will methodically create the adhesive spiral threads. It will use the initial radiating lines as well as the non-sticky spirals as guide lines. The spaces between each spiral will be directly proportional to the distance from the tip of its back legs to its spinners. The spider uses its own body as a measuring/spacing device. While the sticky spirals are formed, the non-adhesive spirals are removed as they are not needed any more.
After the spider has completed its web, it will chew off the initial three centre spiral threads then sit and wait with its head down, in the web for its prey to come along. If the web is broken without any structural damage during the construction, the spider does not try to remake it as this would use up too much energy and it will probably be taken down in the morning or repaired the next night.
During
World War II the threads of Araneus diadematus, Zilla atrica,
Argiope aurantia and other orb weavers were used as hairs in
measuring equipment. The Americans used the threads of the black
widow (Latrodectus) in their telescopic gun sights.
