Bookworm is a popular simplification for any insect which allegedly bores through books. Definite book-borers are rare. Both the larvae of the death watch beetle (Xestobium rufovillosum) and the general furniture beetle (Anobium punctatum) will tunnel through wood and if paper is close by they will go by into that.

A main book-feeding insect is the booklouse (or book louse). A tiny (under 1 mm), soft-bodied wingless psocoptera (generally Trogium pulsatorium), that truly feeds on molds and other crude matter found in ill-maintained works, although they will as well attack bindings and other parts. It is not really a true louse. Lots of other insects, like the silverfish (Lepisma saccharina) or cockroach (various Blattodea), will use these molds and as well degraded paper or else the starch-based binding pastes – warmth and moisture or high dampness are prerequisites, as a result damage is more common in the tropics. Current glues and paper are less striking to insects.