Ohio State University Extension Fact Sheet

Entomology

1991 Kenny Road, Columbus, Ohio 43210-1000

Pseudoscorpions

HYG-2062-98

Common Name	Scientific Name
Pseudoscorpion	Dactylochelifer copiosus Hoff
False Scorpion	Lara granulata (Banks)
Book Scorpion	Pselaphochernes parvus Hoff

Homeowners sometimes become alarmed when discovering tiny scorpion-like creatures with large pincerlike claws, but no long tail and stinger. Some believe they could be tiny, true scorpions, but they are actually pseudoscorpions, which are quite harmless to humans and animals. They can walk backward as well as forward, and normally occur where moisture is present such as in sinks, bathtubs, drains, between book pages, in stacks of newspapers, etc. Occasionally, they become stranded or trapped in sinks or bathtubs unable to climb out over the smooth surface. Others may be found outdoors in mulch, moss, leaf litter, under stones, under tree bark, in manure, between boards in buildings, etc.

Identification

Pseudoscorpions are between 1/16 to 1/8 inch (2 to 8 mm) long, flat-bodied arachnids with a short, usually oval abdomen (11 or 12 segmented) rounded posteriorly. They have a pair of large pincerlike claws (pedipalps) that project forward from the front of the body. There is no curved upward stinger from the rear tip of the abdomen as found in true scorpions. The body color ranges from yellowish-tan to dark-brown, with the paired claws sometimes black. Some have 2 or 4 eyes while others have none. Legs are 5-segmented.

Life Cycle and Habits

Pseudoscorpions are rather common but rarely seen due to their secretive habits and small size. They have the habit of attaching themselves (not as parasites) to the legs and appendages of flies, beetles and other insects, which permits them to "hitchhike" into the home. Some are found under the wing covers of long-horned beetles, where they prey on mites found on the beetles' bodies. The pincerlike pedipalps contain well-developed venom glands and ducts in the movable part of the pincer, which are usually absent in the fixed part. The poison is used solely to capture small insects (their prey). They do not bite. They have silk gland openings on their jaws, and use silk to make chambers for overwintering, molting or brooding.

Males produce a spermatophore (packets of sperm), and the female is pulled over it during the mating dance. Eggs, in a little sac or brood pouch, stay attached to the female's abdomen and after young hatch, they ride on the mother for a short time. Usually there are fewer than two dozen young, but there may be more than one brood per year. Young molt three times, taking one to several years to reach adulthood. Adults may live for 2 to 3 years and are active in the spring, summer and autumn, overwintering in silken cocoons.

Pseudoscorpions are considered beneficial to humans since they are aggressive feeders (predators) on clothes moth larvae, carpet beetle larvae, booklice, ants, mites, small flies and even small earthworms.

Control Measures

Usually no control measures are needed. Simply collect individual pseudoscorpions with a broom and dustpan or by some other mechanical means and discard. Outdoors, these creatures are an important part of the micropredator fauna of soil, leaf litter and bark. Effort should be made to eliminate their prey such as clothes moth larvae, carpet beetle larvae, booklice, ants, mites and flies, which will discourage pseudoscorpion infestations. Usually only 1 to 2 pseudoscorpions are detected in the home over long periods of time (months, years). Again, they cause no harm to the homeowner, but may be a nuisance by their presence.

NOTE: Disclaimer - This publication may contain pesticide recommendations that are subject to change at any time. These recommendations are provided only as a guide. It is always the pesticide applicator's responsibility, by law, to read and follow all current label directions for the specific pesticide being used. Due to constantly changing labels and product registrations, some of the recommendations given in this writing may no longer be legal by the time you read them. If any information in these recommendations disagrees with the label, the recommendation must be disregarded. No endorsement is intended for products mentioned, nor is criticism meant for products not mentioned. The author and Ohio State University Extension assume no liability resulting from the use of these recommendations.