Why do we have spiders according to Greek mythology?

According to Greek mythology, the origin of the spider
came about as the result of a lost contest and the resulting suicide. In the story of
Athena and Arachne, Arachne
was a talented weaver who believed that her skill was even greater than that of the
Goddess Athena. So, Arachne (which means "spider" in Greek) challenged Athena to a
weaving contest. Both works were magnificent: Athena wove an image of her victory over
Poseidon; Arachne's tapestry displayed 21 examples of infidelity among the gods.
Arachne's finished product was deemed perfect by Athena, but the subject matter
infuriated the goddess. Athena destroyed Arachne's tapestry and cursed her to live out
the rest of her life in overwhelming guilt. Arachne eventually hanged herself. In
response, Athena--using the juice of wolfsbane--reincarnated Arachne as a spider which
retained Arachne's weaving abilities.