Question

how does mythoogy explain spiders?

Answer 1

I depends on what form of mythology you are referring to.
The best type of mythology I know is Greek mythology. They explain spiders using the story of how the goddess Athena turned Arachne, a mortal maiden who had attained such skill in the arts of weaving and embroidery, into a spider. Arachne had challenged Athena at weaving, mostly to prove to the goddess that she would be better. Athena won regardless, and turned Arachne into a spider, or, an arachnid, so she would do nothing but weave webs the rest of her life.
It is truly an interesting tale; look it up! :)