spiders are orb weavers, known for their intricate orb-shaped webs. Web building
is a complex process: support lines are constructed first; then the radial
lines; and finally the spiraling strands are spun from the center outward.
Without training from adults, even the tiniest just-hatched spiderlings are able
to spin silk and weave webs. Another orb weaver, nephila, builds an
extremely thick and strong web, up to eight feet in diameter. People in
Southeast Asia have found an interesting use for this spider's web -- they bend
a pliable stick into a loop and pass it through the large web, resulting in a
surprisingly strong and effective fishing net!|
Spiders produce silk from glands called spinnerets. Orb weavers can have
three or four pairs of these glands, each producing different textures of silk:
non-stick silk for the radial web lines, and sticky silk for the spiraling
strands. Some spiders even produce an ultraviolet silk to attract insects.
Spider silk, a super protein that hardens as it is stretched from the
spinnerets, may look delicate but it is unbelievably tough. The relative tension
necessary to break it is far greater than for steel.
When finished with the construction of its web, the garden spider will often
go to the center, hang upside down, and wait for a flying or jumping insect to
become ensnared. Having poor eyesight, orb weavers rely on a highly-developed
sense of touch. When an insect becomes caught in the web and struggles, the
spider is alerted by the vibrations. It rushes out to secure its prey, usually
wrapping it in silk. A poison is injected into the victim, paralyzing it and
converting the contents of its body to liquid. The spider returns later to
insert its tube-like fangs and suck up its meal.
The garden spider's profound sense of touch has another purpose: it provides
male spiders with a channel to communicate with females. Before climbing onto
the female's web, the male taps out a special message. Then he cautiously crawls
toward his mate -- a perilous task, for he is always in danger of being mistaken
for prey. It is commonly thought that the female spider kills and eats the male
after mating, but this is an exaggeration. The male, who stops eating during his
mate-hunting ordeal, generally dies of malnourishment and exhaustion.
Spiders are similar to, but not the same as insects. They belong to the class
Arachnida, named after Arachne, a maiden in Greek mythology. She defeated
the goddess Athena in a weaving contest. In a fury of anger, Athena destroyed
Arachne's weaving and beat the girl about the head. In utter disgrace, Arachne
hanged herself. A regretful Athena changed Arachne into a spider so that she
could weave forever.
While they are certainly not going to win any popularity contests, spiders'
insect-eating habits are extremely helpful to humans. Every year, billions of
spiders do away with a large number of disease-carrying and crop-destroying
insects. If every spider ate just one a day for a year, those insects, piled in
one spot, would weigh as much as 50 million people. Spiders are, by far, the
most important predator of insects in our world.