What does "indusial" mean?

Indusial: Of, pertaining to, or containing, the petrified cases of the larvæ of certain insects. Indusial limestone (Geol.), a fresh-water limestone, largely composed of the agglomerated cases of caddice worms, or larvæ of caddice flies (Phryganea). It is found in Miocene strata of Auvergne, France, and some other localities.