Pseudoscorpions

Published by Utah State University Extension and Utah Plant Pest Diagnostic Laboratory ENT-127-08 July 2008 

Erin W. Hodgson 

Extension Entomology Specialist 

What You Should Know 

• Pseudoscorpions are harmless to people and pets. 

• They “hitchhike” on flies and beetles, and sometimes 

can accidentally enter the home. 

• Pseudoscorpions are considered beneficial to humans 

because they feed on clothes moth larvae, carpet 

beetle larvae, booklice, ants, and mites. 

Pseudoscorpions, also known as false scorpions 

or book scorpions, are arachnids in the order 

Pseudoscorpionida. There are more than 3,300 

different species of pseudoscorpions throughout the 

world, with the most dense populations found in the 

tropics and subtropics. They can be found throughout 

Utah. As the name suggests, pseudoscorpions look 

very similar to scorpions except they do not have a 

stinger at the end of the abdomen like true scorpions. In 

general, pseudoscorpion adults range from 2 to 8 mm in 

length, and have flattened, pear-shaped bodies (Figs. 

1-5). They have four pairs of legs and a pair of large 

pedipalps, that protrude forward from the front of the 

body. The pedipalps 

have venoms glands 

used for subduing 

prey. Pseudoscorpions 

also have mouthparts 

called chelicerae 

that help break down 

food and spin silk. 

The body color varies 

from yellowish-tan to 

dark-brown; however, 

the pedipalps are 

typically black. Some 

species have two to 

four eyes while others 

have none. 

Fig. . A pseudoscorpion 

collected from a home in 

northern Utah in 2007. 

Pseudoscorpions 

Brooke Lambert 

Alan H. Roe 

Insect Diagnostician 

Fig. 2. A pseudoscorpion, Chelifer cancroides, 

note the enlarged pedipalps for grasping prey. 2 

Life Cycle 

Pseudoscorpions have an extended life cycle of 1 to 3 

years, depending on the location and temperature. The 

mating ritual for pseudosporpions is similar to the dance 

of true scorpions. The male pseudoscorpion produces a 

spermatophore, or sperm packet, and pulls the female 

over it during the mating dance. The female carries a 

silken egg pouch of 12 to 24 eggs on her belly for about 

3 weeks. The hatched 

brood ride on the 

females back until they 

get older. The young 

look like the adults 

except smaller; they 

will molt three times 

over several years 

before becoming 

adults. Adults live 

for 2 to 3 years and 

females may produce 

several broods a year. 

Pseudoscorpions 

overwinter in silken 

cocoons. 

Fig. 3. Pseudoscorpion. 3 

page

UPPDL, 5305 Old Main Hill, Logan UT 84322-5305 T: 435.797.2435 F: 435.797.8197 www.utahpests.usu.edu 

Habitat Description 

Pseudoscorpions are harmless to people and animals. 

They normally occur where moisture is present, such 

as in sinks, bathtubs, and drains. They have also 

been found between book pages and in stacks of 

newspapers. Outdoors they have been found in mulch, 

moss, leaf litter, under stones, under tree bark, in 

manure, and between boards in buildings. 

Pseudoscorpions are most active during warm days 

in the spring, summer, and fall. Pseudoscorpions are 

common, but not seen or recognized often due to their 

size. These arachnids are not very mobile, but they will 

attach themselves to the legs of flies, beetles, and other 

insects. As they “hitchhike” to new habitat, they can be 

accidentally introduced inside structures. 

Pseudoscorpions cannot bite people or pets and should 

be considered beneficial. The young and adults feed 

on clothes moth larvae, carpet beetle larvae, booklice, 

ants, mites, small flies, and small earthworms. Like true 

scorpions, pseudoscorpions inject venom into prey and 

ingest the liquefied remains. 

Fig. 4. Pseudoscorpion. 4 

Image courtesy of Erin Hodgson, Utah State University Extension (www.utahpests.usu.edu). 

2 Image courtesy of Chris Buddle (www.biology.ualberta.ca/bsc/news24_1/pseudoscorpions.htm). 

3 Image courtesy of Key Gray collection at Oregon State University (www.uidaho.edu/so-id/entomology/Spiders.htm). 

4 Images courtesy of the Backyard Arthropod Project (http://somethingscrawlinginmyhair.com/category/arthropods/arachnids/pseudoscorpions/). 

5 Image courtesy of Bill Capman (http://www.augsburg.edu/biology/photoofmonth/pseudoscorpion.html). 

Management 

Control methods for pseudoscorpions are usually not 

warranted; however, exclusion of insects and arachnids 

in structures is generally encouraged. Efforts should be 

made to reduce accidental migration inside the home. 

Minimizing pseudoscorpion prey availability will also 

discourage infestations. 

• Eliminate places where pseudoscorpions live will also 

help. Dry out damp areas in the house (e.g., laundry 

room, furnace, bathroom, etc.), and around the exterior 

perimeter. 

• Caulk or seal openings or foundation cracks, windows, 

and around plumbing, gas, or electrical conduits. 

Use weather stripping around doors and windows. 

Expanding-foam sealants may be of value in protecting 

hidden recesses and other areas not readily visible. 

• Completely sealing any structure may be impossible. 

If needed, collect individuals with a broom and dustpan 

and discard or simply vacuum any pseudoscorpions 

found in the home. 

Fig. 5. Size comparison of a dime 

and a pseudoscorpion. 5 

Precautionary Statement: All pesticides have benefits and risks, however following the label will maximize the benefits and reduce risks. Pay attention to the 

directions for use and follow precautionary statements. Pesticide labels are considered legal documents containing instructions and limitations. Inconsistent 

use of the product or disregarding the label is a violation of both federal and state laws. The pesticide applicator is legally responsible for proper use. 

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age (40 and older), disability, and veteran’s status. USU’s policy also prohibits discrimination on the basis of sexual orientation in employment and academic related practices and 

decisions. USU employees and students cannot, because of race, color, religion, sex, national origin, age, disability, or veteran’s status, refuse to hire; discharge; promote; demote; 

terminate; discriminate in compensation; or discriminate regarding terms, privileges, or conditions of employment, against any person otherwise qualified. Employees and students 

also cannot discriminate in the classroom, residence halls, or in on/off campus, USU-sponsored events and activities. This publication is issued in furtherance of Cooperative Extension 

work, acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, Noelle E. Cockett, Vice President for Extension and Agriculture, Utah State University. 

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Pseudoscorpions

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