Booklouse

• It reproduces by parthenogenesis and almost all its populations lack males: each female produces clones of herself, which lets it colonise a whole store from a single individual.
• Its presence indicates high humidity: it disappears if the space is ventilated and dried out, because it depends on fungi that need that moisture.
• It is a serious pest in archives, libraries and natural history collections, and in the food industry too, where it contaminates stored grain.
• For decades only females were known: it reproduces by parthenogenesis and populations are almost entirely female. The first male was not found until 2002, in Hawaii.
• Every parthenogenetic line analysed carries an endosymbiotic bacterium of the genus Rickettsia, absent from those that do reproduce sexually, which points to the bacterium causing the parthenogenesis.
• It is tiny — around a millimetre — and wingless, and goes unnoticed until the population explodes.
• It can cause a 9.7% weight loss in cracked wheat grain over three months, and carries pathogenic micro-organisms and allergenic proteins.
• In 2019 it was identified as a predator of mosquito eggs in an FAO and IAEA laboratory.

Skeleton type

Invertebrate - chitin exoskeleton (insect)

Habitat and environment

Books, herbaria, grain stores and damp corners of houses

Size at birth

The egg measures a third of the length of the adult

Sexual maturity

The nymphs go through four moults and reach maturity at around 40 days

Gestation / incubation

Embryonic development lasts from 6 days at 32.5 °C to 14 days at 20 °C

Litter / clutch size

About 200 eggs per female over her lifetime; most populations are parthenogenetic and made up only of females

Sources consulted: Perlman et al. · Yang et al. (2015), Scientific Reports · Bai et al. (2025), Insects · Ficha de especie de Liposcelis bostrychophila (Wegiriya) · NCBI PMC4444836 · Oklahoma State University, ficha de psocidos de productos almacenados (Wang et al. 2000) · LSU AgCenter · iNaturalist · LSU AgCenter, ficha Liposcelis bostrychophila · Oklahoma State University (Turner 1994)