Book-lice

Definition

Common name for psocid insects (order Psocodea), small, soft-bodied, often wingless or short-winged insects that feed on molds, fungi, detritus, and organic debris. The name derives from their frequent occurrence in old books, where they consume starch-based glues, sizing, and microscopic molds on paper and bindings. Book-lice include both free-living species in leaf litter and bark (family Psocidae) and domestic species associated with stored products and human habitations (families Liposcelididae, Trogiidae). Despite the name, they are true insects unrelated to parasitic lice (Phthiraptera).

Etymology

From their association with old books and paper products; 'lice' reflects superficial resemblance to true lice in small size and flattened body form, not phylogenetic relationship.

Example

Liposcelis bostrychophila (family Liposcelididae), a common domestic book-louse, infests grain stores and herbarium collections, causing damage to dried plant specimens and stored food products.

Synonyms

• Psocids
• barklice (when referring to outdoor species)
• paper lice

Related Terms

• Psocodea
• Psocoptera
• Liposcelididae
• Trogiidae
• stored-product insects
• museum pests
• Phthiraptera
• dermestids

Usage Notes

The term 'book-lice' is applied inconsistently: some specialists restrict it to domestic psocids (Liposcelididae, Trogiidae), while others use it broadly for all Psocodea. The outdoor relatives of book-lice are often called 'barklice' or 'barkflies.' Book-lice are frequently confused with true lice (Phthiraptera) by non-specialists, but they are not parasitic and do not bite humans or animals. In pest management contexts, 'book-louse' typically signals humidity problems, as these insects require moist conditions and die in dry environments.