I Discovered these larvae in shelf fungus I had broken off a recently fallen dead birch. I had examined some of these shelf fungi at the time, finding nothing inside them, and discarded them in a plastic grocery bag. Yesterday during a household trash roundup I decided to have another look before setting them out for trash pickup.

Yuck! They were a ghastly, moldy mess. I began tearing them apart anyway and soon found these long-bristled larvae. Several crawled up out of the fungus like ants, as if to explore and find out what was happening to their home.

The two tail hooks make me think these are tenebri*onid larvae, which of course is what Bolito*therus are.

Perhaps I didn't see them at once because they were so tiny at the time, or even unhatched. But the warmth inside the house might have speeded their hatching or development. At any rate, I'm hanging onto the fungus to see what they become.