Pseudoscorpion

Pseudoscorpions make up their own arachnid order, Pseudoscorpiones, with more than 3,000 described species worldwide, ranging from tropical forests to caves, deserts, and temperate woodlands. Chelifer cancroides, sometimes called the house pseudoscorpion or book scorpion, is one of the most widely distributed and commonly encountered species, occasionally found indoors among stored papers, an association that gives it its "book scorpion" nickname.

Despite the resemblance in name and general body plan, pseudoscorpions are not closely related to true scorpions in the sense of sharing a stinging tail; they lack a tail and stinger entirely, relying only on their pincers and, in some species, mild venom delivered through those pincers to subdue very small prey.

• Miniature, flattened, oval body typically only a few millimeters long
• Large, prominent pincer-like pedipalps relative to body size, resembling a tiny scorpion's claws
• No tail and no stinger of any kind
• Brownish to reddish body color
• Eight legs, like all adult arachnids
• Easily overlooked due to small size; often mistaken at a glance for a tick or small spider until the pincers are noticed

Pseudoscorpions are found worldwide in leaf litter, soil, under loose tree bark, in bird and mammal nests, and in caves. Some species also turn up indoors in houses, particularly among old stacks of books, papers, or stored items, where they hunt the tiny insects that live in similar dusty habitats.

These are active predators of even smaller arthropods, including mites, booklice, springtails, and small insect larvae, which they seize with their pincers. Many species produce silk from glands near the mouth, which they use to build small nest-like chambers for molting, overwintering, or waiting out dry conditions. Some pseudoscorpions also practice phoresy, hitching a ride by grasping onto the legs of larger flying insects such as flies or onto harvestmen to disperse to new habitats. As predators of small insects like booklice, they can be considered beneficial in the structures where they occasionally turn up.

Mating in pseudoscorpions often involves an elaborate courtship in which the male deposits a stalked packet of sperm (spermatophore) that the female picks up. She then carries the fertilized eggs, and later the newly hatched young, in a brood sac attached to the underside of her abdomen until they are ready to disperse. Young pseudoscorpions resemble miniature adults and undergo several molts before reaching maturity; adults of some species can live two to three years.