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8. Essential Pseudoscorpion Info

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8. Essential Pseudoscorpion Info FACTSHEET 8 Essential pseudoscorpion info Advancing Arachnology Gerald Legg Gerald Common Chthonid (Chthonius ischnocheles) Pseudoscorpions, or false scorpions, are formidable but tiny and rarely seen predators that hide away in soil, leaf-litter, compost, rotting wood and old nests. Pedipalps – for catching prey, preening and defence In Britain we have 26 known Cephalothorax – a hard body part with the eyes species (a 27th is listed, but (if present), pedipalps with scorpion-like pincers, hasn’t been found for decades). chelicerae and legs Not spiders but closely related Chelicerae – jaws Pseudoscorpions are arachnids. Like spiders, they have four pairs of jointed walking legs and another pair of jointed appendages (pedipalps) either side of a pair of powerful jaws (chelicerae). Unlike spiders though, the pedipalps are huge, with scorpion-like pincers; Abdomen – a hence the name ‘pseudoscorpion’. Some soft body part species have poison glands in their pedipalps which expands and contracts and inject venom to subdue their prey. according to how Different species catch different prey. Those well-fed the with stout, muscular pedipalps prefer insects pseudoscorpion is and, in females, that have a hard body and move slowly, whether she contains eggs. Large Tree Chernes (Dendrochernes cyrneus) species produce silk, used to make FACT chambers in which to including some kinds of beetle. Species with moult, hibernate or long, delicate pedipalps catch soft-bodied look after their young. insect larvae, tiny worms and other similar FILE These chambers can Size: Our largest creatures. They are also excellent mothers, sometimes be found pseudoscorpion, the taking care of their young and feeding them beneath tree bark. In Large Tree Chernes (see Life History, right). contrast to spiders, (Dendrochernes which produce silk Where they live cyrneus) measures from spinnerets at the Most terrestrial habitats will have over 4 mm long rear of the abdomen, pseudoscorpions. They even live on the whilst our smallest, pseudoscorpion silk seashore, hiding in rock crevices and under the Book Scorpion comes from a special stones down to the mid-shore level, and (Cheiridium knob or tube (the coming out to feed when the tide recedes. museorum), is only galea) on the tip of a They exploit two types of habitat. Permanent 1.3 mm long. moveable ‘finger’ on habitats used include woodland leaf litter, soil Escape: Touch a the jaw (chelicera). and Sphagnum bogs. They also live among pseudoscorpion and it Breathing: Oxygen is Legg Gerald is likely to run as fast taken into the Book Scorpion backwards as it does abdomen through (Cheiridium forwards. The long museorum) tiny holes (spiracles) sensory hairs that connect to a (trichobothria) on the network of fine tubes rear-end enable it to (trachea) distributed know what is lurking throughout the body. behind. A similar system is Silk: Some found in insects. pseudoscorpion Gerald Legg Gerald mosses and lichens, in grass tussocks, and beneath stones. More transient or temporary habitats include under tree bark, and in rotting wood, manure and Mature male genital area Mature female genital area compost heaps, buildings (thatch and old debris), and in bird and mammal nests. Life history They may also live among stored Adult males can be distinguished from females products in barns, warehouses and old by their more complex and distinctive genital buildings. Aristotle found these living in area on the underside of the abdomen; his library more than 2000 years ago. St ev immature pseudoscorpions have no visible Hitchhiking e Woodward structures in this region. To move around, those in soil and leaf Mating involves no direct sexual contact; the litter just walk, but those in transient male would be a nice meal for the female so he habitats, like compost heaps, keeps away or stays at arm’s length! Instead, hitchhike! They attach themselves sperm are transferred to the female indirectly. to flies, beetles, parasitic wasps The male produces a silk-wrapped ‘packet’ of (see right, pseudoscorpions Gerald Legg Gerald sperm on a stalk (a spermatophore) that he arrowed) and harvestmen deposits on the ground. and get a lift to a new The female picks up the habitat, a process sperm packet from the known as phoresy (from the top of the stalk with her Greek word for ‘being carried’). genitalia. Food and feeding Some species fertilise As aggressive hunters, pseudoscorpions their eggs soon after catch their prey using their formidable mating whilst others pedipalps and chelicerae, which vary in store the sperm for shape and size depending on their future use. By storing favoured prey. Once caught, the prey is sperm these species chewed and digestive juices are poured can exploit temporary onto it. The resulting soup is then sucked habitats such as a up into the mouth. rotting log, compost heap or bird’s nest, Senses allowing a single Although many species have eyes, these Spermatophore (just over 1mm high) of Book female carrying eggs are only sensitive to varying light levels. Scorpion (Cheiridium and sperm to start a For pseudoscorpions to navigate museorum) new population. accurately, and to find prey and mates, The female does not abandon her eggs but they feel their way using long sensitive instead keeps them glued together attached to hairs (trichobothria), many of which are her genital opening. They hatch as minute on the pedipalps. Thin pits sensitive to replicas of the adults (protonymphs) which chemicals are scattered over the body remain attached to the mother and are fed with and provide a sense of ‘taste’. These are ‘milk’ produced by the ovaries. known as the lyriform organs. Pseudoscorpions can detect the acids The young pass through two more, usually free- and sugars produced by the microbial living, nymphal stages before becoming adult. decay of leaf litter and wood. They use In some species the protonymphs remain with these tastes/scents to guide them to their mother inside a silken chamber, and good habitats and likely sources of prey. therefore have never been seen in the wild. Gerald Legg Gerald Common Tree Chernes (Chernes cimicoides) n For more information Weygoldt, P. (1969) The Biology of Pseudoscorpions. Harvard University Press, Cambridge. Legg, G. (1988) Pseudoscorpions. Synopses of the British Fauna (New Series) No. 40, Linnean Society, London. Legg, G. and Farr-Cox, F. (2016) Illustrated key to the British False Scorpions (Pseudoscorpions). AIDGAP/FSC Publications, Telford. UK species: www.chelifer.com/?page_id=81 The British Arachnological Society The BAS is Britain’s only charity devoted exclusively to spiders and their relatives. We use science and education to advance the wider understanding and appreciation of arachnids, and to promote their conservation. Find us at: www.britishspiders.org.uk, www.facebook.com/BritishSpiders or on Twitter @BritishSpiders actsheet text by Gerald Legg, Geoff Oxford and Helen Smith, edited by Nicky Rowbottom, designed by Colin Edwards Graphic Desig Graphic Edwards Colin designed by Nicky Rowbottom, by and Helen Smith, edited Legg, Geoff Oxford Gerald by actsheet text Registered Charity - England and Wales No. 260346, Scotland No. SC044090 F.
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