Fibroin is an insoluble
protein present in
silk created by spiders, the larvae of
Bombyx mori, other moth genera such as
Antheraea,
Cricula,
Samia and
Gonometa, and numerous other insects. Silk in its raw state consists of two main proteins,
sericin and fibroin, with a glue-like layer of sericin coating two singular filaments of fibroin called brins.