Which insects are also called book lice because they feed on the mold that grows on book sizing?

Psocids are commonly referred to as "book lice" because they thrive in environments where mold grows, including on book materials that may have been sized with starches or other substances. These insects are small, soft-bodied, and typically found in damp places where mold can flourish. Their dietary preference for organic matter, particularly the mold that can develop on paper or cardboard, links them directly to libraries and homes where books are stored.

In contrast, the other options do not share this specific dietary habit or association. Grain mites, for example, are known to infest stored grains and are primarily a concern in food storage rather than in relation to books. Dust mites are more prevalent in areas where organic debris accumulates, such as bedding and carpets, rather than specifically feeding on mold on books. Firebrats, on the other hand, are associated with warm, humid environments but do not feed on mold in the same manner as psocids do. Therefore, the designation of psocids as book lice underscores their unique ecological niche and feeding behavior.