Introduction

Pseudoscorpions are tiny, short-bodied arthropods in the Class Arachnida. Like other arachnids (e.g. spiders and harvestmen), they have four pairs of legs and a pair of sensory pedipalps, one either side of the chelicerae or jaws. The pedipalps of pseudoscorpions are greatly enlarged and modified to terminate in large scorpion-like pincers. Unlike scorpions, the pseudoscorpions have no tail with a poisonous sting at the end although some species do have poison glands in their claws.

Not all species have eyes and in those that do, the eyes are only sensitive to light levels. All pseudoscorpions have sensitive hair-like structures on various parts of their bodies called tricobothria with which they detect their surroundings and find prey.

Pseudoscorpions have a silk gland and spin a silken cocoon in which to moult, mate and where the female retreats ready for when her eggs hatch. The baby pseudoscorpions (called protonymphs) stay with their mother in her silken nest and she feeds them on ‘milk’ produced from her ovaries. Pseudoscorpions go through two further nymphal stages (deutonymph and tritonymph) before their final moult into adulthood. They can live for two or three years.

Where to find Pseudoscorpions

Pseudoscorpions are active predators which feed on a variety of invertebrates. They can be found in leaf litter, compost heaps, under logs and stones and beneath tree bark. Some are found amongst mosses while others inhabit the nests of birds. Several are synanthropic, associated with barns and buildings and a few are restricted to the seashore where they can be found under driftwood or at the base of vegetation.

Their tiny size (most are barely 2 or 3 mm long) allows them to hitch a ride on other animals including invertebrates such as flies and harvestmen to move around, known as phoresy. This enables them to exploit ‘temporary’ habitats like bird’s nests, hitching a ride out at the end of the nesting season.

Most species of pseudoscorpion freeze when first found making them difficult to spot even when you are actively looking for them. When they do move, it is extremely rapidly and they can run just as fast backwards as forwards in order to escape danger.

So far, twenty-seven species have been found in Britain. A number of species can be identified with a hand lens but a microscope is needed for most.

The FSC fold-out chart by Gerald Legg and Francis Farr-Cox has a key to the British species. More information can be found on Chelifer.com and on the British Arachnological Society website.