Pseudoscorpions

Overview

[1]

Female Gymnobisium species-size reference.[3]

Pseudoscorpions, also known as false scorpions, are very small arachnids with pincer-like appendages resembling those of scorpions. These pedipalp appendages function similarly to claws and are relatively large in comparison to their overall size. Generally reaching about 2-8 millimeters in length, pseudoscorpions often go unnoticed or are commonly mistaken as ticks. Pseudoscorpions are not regarded to be harmful. In fact, they prey upon many small arthropods, aiding with pest control. [1] There are over 3,300 identified species of Pseudoscorpions, 200 of which inhabit North America. [4]

Classification

• Kingdom- Animalia (Animals)
  • Phylum- Arthropoda (Arthropods)
    • Subphylum- Chelicerata (Chelicerates)
      • Class- Arachnida (Arachnids)
        • Order- Pseudoscorpiones (Pseudoscorpions)

Characteristics and Morphology

• A common house pseudoscorpion is usually between three and four millimeters.
  • Color: yellowish to a brown
  • Body: 12- segment abdomen, which only 10 are visible. These segments are protected by plates made of chitin.
    • Shape: flat teardrop or pear like shaped body
  • Pedipalps: Claw like. over twice the length of their legs. If they were completely extended, they would measure about seven to nine millimeters across. [1]
    • Making up their pedipalps is an immobile hand and a finger. Separate moveable fingers are controlled by the adductor muscles. A venom gland and venom duct are usually also located in the mobile finger. This venom is used during hunting. The pseudoscorpion uses this venom to immobilize and and capture their prey. While digesting, they pour their semi-corrosive saliva over their prey to aid in a smooth digestion, then they eat the liquid remains. This mechanism helps them feed, but it is not harmful to humans or other pets. [4]
  • When they move, they walk crab like. Interestingly, they can move as fast backwards as they can forwards.
  • They have a gland in their jaw that spins silk. This silk makes cocoons for mating, molting, or to keep warm in cold weather.

[7]

Pseudoscorpions superficially resemble true scorpions, but, they lack the elongated metasoma (tail). [3] Also unlike scorpions, pseudoscorpions have no sting on the end of their flat and oval-shaped abdomens. [6] A big difference between the two is also size. Pseusoscorpions are so small, that they usually go unnoticed. Scorpions are recognizable when seen. One of the most important features for these creatures are their pedipalps, which both of these creatures have.

Reproduction

The males produce sperm, which is then packaged and planted for the female. Males of most families that have been studied just deposit a spermatophore without engaging or even in the presence of a female. The females find this and draw it in. Males of Serianus do deposit in front of the female, but there is no physical connection between the two. The members of the Cheliferoidea perform an elaborate mating dance, where males actively call to females, taking the female using his pedipalps. He then deposits a spermatophore and assists the female to move over the spermatophore, where she will draw it in. Later on, the eggs then mature internally. [5]

Distribution

Pseudoscorpions are found worldwide. These organisms range from the tropical regions of the globe, where the densest and most diverse populations are found, to the temperate cold regions. Pseudoscorpions have spread to island territories as well, with endemic species being recorded in the Canary Islands and the Maltese Islands. These arachnids can be located dwelling in many different types of habitats and environments. Species are found under tree bark or within tree hollows, in the soil and leaf litter, under stones, inside caves, on ocean shores, and within buildings and homes.

[7] Drawings of a pseudoscorpion and a scorpion from JH Comstock’s book. Note that the scale is different for each drawing.

References

[1] Jacobs, S., Sr. (2013). Pseudoscorpions (Department of Entomology). Retrieved from http://ento.psu.edu/extension/factsheets/pseudoscorpions

[2] Mosco, R., & Wicks, M. (n.d.). Book Scorpion [Cartoon]. In Your Wild City.

[3] Neethling, J. A. (n.d.). Pseudoscorpions: Cryptic Predators of the Soil. Retrieved from http://sergsa.org/pseudoscorpions-cryptic-predators-soil/

[4] Hahn, J., & Kells, S. (2018). Pseudoscorpions in homes. Retrieved from https://www.extension.umn.edu/garden/insects/find/pseudoscorpions/

[5] Government of Western Australia. (n.d.). What are pseudoscorpions? Retrieved from http://www.museum.wa.gov.au/catalogues/pseudoscorpions/what-are-pseudoscorpions

[6] Lewis, D. (n.d.). The Benefits of Pseudoscorpions. Retrieved from https://www.extension.iastate.edu/news/2008/mar/071001.htm

[7] Comstock, J. H., & Gertsch, W. J. (1980). The spider book: A manual for the study of the spiders and their near relatives, the scorpions, pseudoscorpions, whip-scorpions, harvestmen, and other members of the class arachnida, found in America North of Mexico, with analytical keys for their classification and popular accounts of their habits. Ithaca: Comstock.