The silk mycostrum evolved alongside the silk knightworm, together colonizing the mountains of Barlowe. The silk mycostrum's biggest changes came as they adapted their reproductive strategy. They already formed networks of strands, which could form into thicker fur-like fibers. In its new environment, with frequent precipices and channels, it was useful to be able to spread across such gaps. As a result, they adapted to be able to shoot out these strands, dense and strong like spider silk and similarly able to extend their network. This became their primary means of dispersal, as they could spread far and wide when caught in the wind, and strands could easily detach and grow into a separate organism. They form fruiting bodies much less frequently: only where they've grown to maximum size or have formed a stable nest. They also frequently exchange genetic material by conjugation when coming in contact with other bits of silk mycostrum, which happens more frequently now that they're frequently spreading to new areas via exploratory offshoots.

A "bridge" of silk mycostrum.

They continue to live in close association with silk knightworms, though this is not necessary for their survival. They'll cover the knightworm in their symbiote form, in insulating wooly fibers. They also form nests that their symbiotes can rest in, usually in the middle of bladebushes. This is seen in the main illustration, where it has formed fruiting bodies and is host to some silk knightworm eggs. In their symbiote form, they'll often brush against other symbiotes or nests or free strands, which increases chances to exchange genetic material. Silk mycostrum benefits from the association as they can feed off of excess exoskeletal material and feces. They've also been selected for increased tensile strength so they can support silk knightworms when using the strands to cross from location to location.