Pseudoscorpion

Pseudoscorpions have a flat, pear-shaped body. They have 4 pairs of legs, so they belong to the Class Arachnida. They look like scorpions but have no tail or stinger. The short rounded abdomen has twelve segments. Each segment is protected by a tergite (plate above) and a sternite (plate below).

Because of their very small size—usually less than ¼ inch long—pseudoscorpions are rarely seen. Members of the largest species, Garypus titanius, grow to about ½ inch long.

Most pseudoscorpions have 2 to 4 simple eyes. Albiorix anophthalmus is reported to be the only eyeless species.

Their legs have 5 to 7 segments. Their long pedipalps (pincer-like claws) are similar to the pincers on a scorpion. There are no “teeth” on the pedipalps. Most species have venom glands and release venom from the pedipalps.

The body colors of most pseudoscorpions vary from yellowish-tan to dark brown. Sometimes red or olive tinges and dark markings can be seen. Adults of the eyeless species A. anophthalmus are light brown to tan with a gray area across the upper abdomen.

Members of the Chernetidae family are very small ranging from 1/16 inch to 1/8 inch long. They have 5 segments on their legs and are usually tan to dark brown.

Like spiders, pseudoscorpions have silk glands. The duct openings are located on the chelicerae (jaws).

In North America there are over 350 pseudoscorpion species. About 2,500 species are known worldwide. They live in cold regions like Northern Ontario and above the timberline in the Rocky Mountains. They are most abundant and diverse in warm tropical regions. They are found beneath tree bark, in tree hollows, and in leaf litter. Some species live in the soil. Others live under stones, in cracks of rocks, and in caves. A few species live at the seashore.

Members of the species Chelifer cancroides are commonly found in homes, where they live in between pages of books. They are sometimes found trapped in bathtubs and sinks.

The largest species, Garypus titanius, lives in the middle of the southern Atlantic Ocean on Ascension Island.

Members of the rare eyeless species A. anophthalmus live in areas of complete darkness inside caves where temperature and humidity remain constant. They hide under small pieces of broken limestone scattered throughout the interior of the cave. This species has so far been discovered only in Arkenstone Cave in Pima County, Arizona.

Many pseudoscorpion species eat insects and small invertebrates. The cave-dwelling A. anophthalmus is part of a complex food chain. It eats small invertebrates which feed on mold that grows on cricket guano.

The common household species C. cancroids eats booklice and dust mites. It sometimes feeds on mites that live underneath wing covers of certain beetles.

Most species in the Family Chernetidae have a varied diet. They feed on small flies, bark lice, caterpillars, butterflies, ants, mites, and small earthworms .

In the growing stages, a silken cocoon provides good protection from enemies. As adults, pseudoscorpions can move quickly and easily in all directions to escape predators. Most species have venom glands and release venom from the claw-like pedipalps.

A pseudoscorpion goes through 3 molts over the course of several years before it becomes an adult. The young usually grow inside a small, protective, silken cocoon. They live 2 to 3 years after reaching adulthood. Members of some species can live up to 4 years.

In most species, the female has a brood pouch that remains attached to her abdomen. Hatchlings stay in the pouch and feed on a milk-like liquid from her ovaries. In some species, the female abandons the pouch leaving her embryos to develop unattended.

Pseudoscorpions can clamp onto the leg of a fly or beetle to hitch a ride from habitat to habitat. Hitching a ride on a larger insect is known as phoresy.

They have silk glands and use silk to spin cocoons in which to molt. Silken cocoons also provide shelter during the cold winter months.

Because of their secretive nature and very small size, pseudoscorpions are rarely noticed by people. They are often mistaken for either ticks or small spiders. Pseudoscorpions are neither dangerous nor destructive. They pose no hazard for homeowners.