Yesterday, I needed to make a label for a hat I'd knitted from some 1980's-vintage silk yarn. The search engines showed me this excellent (but not new) article: Silk is the Bomb[yx] (Knitty, Spring 2006) by Michael Cook. Here's what I needed to know:
Species silks, or "wild" (actually semi-domesticated) silks, used to be very hard to find. Nowadays, hand knitters and spinners can get Tussah fibers and yarns in a wide range of colors and preparations, and some vendors even offer Eri and Muga yarns and fibers. Each of these is produced by a different species of moth. In India, which is where most of the wild silks are produced, they are called "vanya" silks; these silks each have a distinctive feel and color, and they are a treat for the hand spinner.