fecal material and/or wood shavings produced by insects.

Merriam-Webster Online Dictionary
frass (noun)
debris or excrement produced by insects
frass (Wikipedia)
Frass in the oak leaf mine of a final instar larva of the moth Ectoedemia heckfordi
The frass of dampwood termites may be a useful sign of an infestation
Galleries of various species of wood-boring beetles typically are stuffed with frass
Typical frass dust from Bostrichid shot hole borer beetles
Typical sculpting of a frass pellet of a large caterpillar
A golden tortoise beetle larva carrying a mass of its own frass as a repugnatorial defence.

Frass refers loosely to the more or less solid excreta of insects, and to certain other related matter.

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