by Piter Kehoma Boll
Spiders, mites, harvestmen and scorpions are the best known arachnids among the general public. However, another group that has a lot of species, even more than scorpions, is that of the pseudoscorpions. There is a very good chance that some of them are living very close to you, especially if we think of Chelifer cancroides, the house pseudoscorpion.
The name pseudoscorpion comes from the fact that these arachnids resemble scorpions, except for the lack of the tail. They are also much smaller. The house pseudoscorpion is brown and measures only about 0.5 cm in length and, as its name suggests, likes to live in human residences.
Male house pseudoscorpions defend a small territory with a radius of only a few centimeters. They allow females to enter their territory and, during the mating period, begin the courtship behavior, by which they initiate a dance and lead the female to a sperm sac (spermatophore) deposited on the ground. The female picks the spermatophore with her genital orifice and use the sperm to ferilize her eggs.
When the eggs are laid, they remain attached to the female genital pore and are covered collectively by a membrane. When the young hatch from the eggs, they are still larvae and remain inside the sac formed by the membrane covering the eggs. The female then secretes a milk-like substance from her uterus and the larvae feed on it. After molting for the first time, the larvae, now first-instar nymphs, leave the mother and, after three more moltings, reach the adult state.
Although it can pass unnoticed most of the time, the house pseudoscorpion is a cosmopolitan and common species living near and insie houses. Its pedipalps, which resemble those of scorpions, are very long and can reach almost 1 cm in length when extended. As most arachnids, they are predators, and their presence in human dwellings can be quite useful as they feed on smaller, annoying creatures, such as mites, bed bugs and booklice.
If you ever find one in your house, be kind and thank them for their service.
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Harvey MS (2014) A review and redescription of the cosmopolitan pseudoscorpion Chelifer cancroides (Pseudoscorpiones: Cheliferidae). Journal of Arachnology 42: 86–104.
Levi HW (1948) Notes on the life history of the pseudoscorpion Chelifer cancroides (Linn.) (Chelonethida). Transactions of the American Microscopical Society 67(3): 290–298. doi: 10.2307/3223197
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