House False-scorpion

• It is known as the book scorpion because it turns up between the pages of old volumes, where it hunts the mites that feed on the paper and the glue.
• It travels long distances by gripping the legs of flies and other insects with its pincers, a form of hitchhiking called phoresy.
• It produces silk, but not from the abdomen as spiders do — from glands in the pincers themselves — and weaves with it a retreat in which to moult and overwinter.
• It is a pseudoscorpion: it has a scorpion's pincers but neither its tail nor its sting, and it is entirely harmless.
• It travels by hitch-hiking. It grips a fly, a wasp or even a bat with its pincers and lets itself be carried elsewhere, a phenomenon called phoresy. That is how it gets into houses, along with the firewood.
• It is called the book scorpion because it turns up in rooms with dusty books, where it hunts exactly what abounds there: booklice and dust mites.
• It has a venom system of its own, in the pincers of its pedipalps, evolved independently of those of scorpions and spiders. Analysis of it has identified peptides with antimicrobial activity.
• It weaves silk chambers in which it moults and overwinters, and the male deposits a spermatophore that the female picks up from the ground.

Habitat & environment

Interiors of houses, libraries, granaries and birds' nests

Gestation / incubation

From egg to adult takes 10 to 24 months, with three moults

Litter / clutch size

From 20 to 40 eggs, which the female carries in a pouch under her abdomen

Sources consulted: Linneo (1758); Krämer et al. (2019 y 2022), Toxicon y Toxins; Bugwood Wiki