Hidden Britain
REVEALING A FASCINATING WORLD OF WILDLIFE THAT WE OFTEN OVERLOOK.
Everything you need to know about pseudoscorpions
My first encounter with pseudoscorpions was a revelation. On the edge of my compost bin, apparently engaged in remote-controlled manoeuvres, were armour-plated miniature scorpions – just minus the stinging tail. Sedate forward progress was broken by sudden reversing or sideways swerves. One look and I was hooked!
In Britain we have 27 species of these immensely engaging invertebrates – varying in length from an impressive 4mm in the large tree chernes to just 1.3mm in the book scorpion. Like spiders and true scorpions they are arachnids, with four pairs of jointed legs and another pair of jointed appendages (pedipalps) each side of their jaws (chelicerae). They usually have one or two pairs of eyes but these are sensitive only to changing light levels; navigation relies on long, sensitive hairs (trichobothria), and on tastes and scents that guide them to good habitats and sources of prey.
Armed and venomous
Relative to the size of the animal, the pedipalps are huge, and end in scorpion-like pincers which give rise to their name. This formidable weaponry is, unsurprisingly, used for defence and prey capture, as well as for grooming. Displaying their arachnid credentials, some species produce venom, ejected from glands at the tips of the pedipalps and capable of subduing prey substantially larger than themselves.
Lying between the pedipalps, the tooth-edged chelicerae are also pincer-like – they provide a powerful bite and filter food. In bizarre contrast to spiders, which produce silk from spinnerets at the rear of the abdomen, some pseudoscorpions produce it from a tiny projection (the galea) at the tip of the chelicera.
Pseudoscorpion silk is restricted to peaceful uses; food is captured by stealth rather than entrapment in silken webs. The all-important pedipalps vary in shape and size depending on the favoured prey, which could include beetles or insect larvae.
Their sex lives are discreet in the extreme to avoid conflict between well-armed parties. The male often has no contact with the female, instead leaving her to collect a tiny, silk-wrapped packet of sperm (a spermatophore) deposited on the ground on a silken stalk just a millimetre high. In some species spermatophore production follows a courtship ‘dance’, sometimes holding ‘hands’ – the pincers.
Motherhood is a serious commitment. Pseudoscorpion eggs mature internally and the embryos are ‘laid’ into a brood-sac under the female’s body where they are protected and nourished. They emerge as perfect miniatures of the adults, undergoing several moults before they mature. In some species the mother continues to feed the free-living nymphal stages with secretions from her mouth. In others she shares a silk chamber with her brood until they mature.
Helpful house guests
Despite their low profile in every sense, pseudoscorpions are found in most terrestrial habitats. Some species exploit transient places such as rotting wood, compost heaps and bird nests, while others prefer the relative permanence of soil, leaf litter and grass tussocks. Some live dangerously, in crevices on the shore, coming out to feed as the tide recedes, while others enjoy the comfort of our homes, feeding on less welcome guests such as carpet beetle larvae, booklice and house dust mites.
Once you’ve focused down and been charmed by your first pseudoscorpion, identification can be challenging. But help is at hand from a new, illustrated key from the Field Studies Council (FSC). You can find out more at http://bit.ly/2gOItLH.