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Extension > Garden > Insects > Pseudoscorpions

Pseudoscorpions in homes

Jeffrey Hahn, Asst. Extension Entomologist
Stephen Kells, Assoc. Professor, Dept. of Entomology

Pseudoscorpions, sometimes called book scorpions, are a type of arachnid related to spiders, ticks, mites, and scorpions. Also known as false scorpions, there are over 3,300 species known in the world and about 200 species in North America. Although they are common, they are not usually noticed by people.

Identification

Pseudoscorpion

Typical pseudoscorpion. Note the conspicuous, pincher-like pedipalps

These arachnids have oval or teardrop shaped, flattened bodies with two conspicuous pedipalps (pincer-like appendages). They are reddish or brown and small, with a body length of about 1/5 inch long (about 3/8 inch long when the pedipalps are extended). When they walk, they often appear crab-like and can move as quickly backward as they move forward. Without their large pedipalps, pseudoscorpions look like ticks. Pseudoscorpions are also similar to scorpions but lack the long ‘tail’ and stinger that are common to scorpions.

Biology

Pseudoscorpions live in many habitats and are often found in cracks, crevices and similar spaces. They typically like high humidity and are found in leaf litter, moss, under tree bark and stones, in bird and mammal nests, and in buildings. They commonly enter homes by hitching rides on larger insects, e.g. flies and beetles (this is habit is known as phoresy), or on firewood. When found indoors, pseudoscorpions can be found in any room in a home, although they are usually more common in relatively damp areas, such as laundry rooms, basements, and bathrooms.

Pseudoscorpions are predaceous, feeding on many types of small insects and other arthropods, including springtails, psocids (barklice and booklice), thrips, beetle larvae, flies, ants, and mites. Many aggressively stalk their prey while others prefer to hide and ambush insects. They generally have poor vision and use sensory hairs on their pedipalps to find prey.

When a small insect brushes against these sensory hairs, it triggers a reaction by the pseudoscorpion to seize the insect. Most pseudoscorpions have poison glands in their pincer-like claws which they use to paralyze prey. They inject saliva into the victim; the pseudoscorpion feeds on the liquefied contents, like a spider or scorpion. The poison gland helps the pseudoscorpions feed but is not harmful to humans or pets.

Pseudoscorpions usually live two to three years. There may be one or two generations in a year.

Importance

Despite their appearance, pseudoscorpions are harmless to people and pets, they cannot bite or sting. They also are not destructive to food, clothes, or property. Pseudoscorpions are mostly commonly seen during spring and summer when it is warm.

Management

In most cases, people do not see more than just a few pseudoscorpions at a time indoors. Physical removal is the only necessary control. If possible, capture them (just slide a piece of paper underneath of it) and release them outdoors.

In the unlikely case that persistent numbers are present, control pseudoscorpions by drying out damp areas with fans or dehumidifiers to make areas less hospitable for pseudoscorpions and their prey.

Because pseudoscorpions are uncommon indoors and are harmless, insecticides are not necessary or recommended.

 

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