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Insects and other arthropods

Pseudoscorpions

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Pseudoscorpions are close relatives of the true scorpions, but smaller in size, with dissimilarity in the extremities of the abdomen.
Photo: Insectarium de Montréal (René Limoges)

Pseudoscorpions look like tiny scorpions with a flat, oval body. Like scorpions, they have a pair of large pedipalps with claws at the ends. However, they have no spur at the end of their abdomen, and the back end of their body is short and rounded (it is elongated and forms a telson on scorpions). They measure 2 to 4 mm long on average. No known species measures more than 8 mm.

Pseudoscorpions have two or four eyes, sometimes none. Their colour varies from yellowish-beige to dark brown. Their claws are sometimes black. The male and female are similar.

Small and effective claws

A well-developed venom gland is located at the end of the claws of pseudoscorpions (usually the mobile end). This gland may be found on both claws or only one of them. Pseudoscorpions use their pedipalps to catch their prey, which are then paralyzed or killed by the venom.

Once its prey has been paralyzed, the pseudoscorpion seizes it with its chellicerae, two hooks on each side of its mouth that destroy the exoskeleton of its prey. Like spiders, pseudoscorpions sucks up pre-digested substances, and part of its digestion takes place in the body of its prey. When it sucks out the inside of its prey, small hairs filter out solid particles so that only liquid passes through. When there are too many accumulated particles, the pseudoscorpion ejects them. After the meal, it cleans its complex mouthparts with comb-shaped structures on its chellicerae.

Pseudoscorpions carry their pedipalps in front of their head when moving. If they are disturbed, they place their claws above their shell and stay still. They are able to move backward.

Pseudoscorpions have glands that produce silk threads used to spin their cocoons. The opening of the silk glands is located on the chelicerae.

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