Silkworms

I was thinking about silkworms the other day. How do they work exactly? Does a person have a silkworm farm? Do you hunt for silkworms in the wild or buy them from a breeder? How is the silk harvested? How many silkworms do you need to own to actually make a profit? Are there different species of silkworm that produce different grades of silk, or is that part based on how the silk is harvested? What's done to silk to transform it from it's raw state? Is there a way to suspend them in the silk producing stage, or do you just have to accept the fact that eventually you'll have an ass load of moths flying around? Some research is in order.