PSEUDOSCORPIONS | False Scorpions

Pseudoscorpions are tiny predatory arachnids commonly known as false scorpions as they lack the tail and stinger of a true scorpion. Although pseudoscorpions have been recorded from a surprisingly wide range of habitats, including seashores, coastal strandlines and sand dunes; salt marsh and bogs; grassland; heathland; and from bird's nests, manure and compost; or even inside buildings; the more likely place you'll find them is in woodland. Whether broadleaved or coniferous, there are a number of species that could be found at ground level living in the soil and leaf-litter or under stones and deadwood, and others that are arboreal living beneath the bark of old or rotting trees.

Twenty-six species are known to exist in Britain and although quite a number of these are rare or poorly recorded there's sufficient distribution data available to have a pretty good idea where each species could be found. The association with both the broader and, more importantly, the actual microhabitat is useful, but it's also worth remembering that some species are phoretic and, consequently, could turn up pretty much anywhere.

So, with all that information, you'd think that pseudoscorpions would be relatively easy to find, but unfortunately they're not as they are so easy to overlook. Their small size allows them to hide in plain sight as their first line of defence when disturbed is

to remain motionless with their legs and pedipalps held tight to their body. You really need to spot them at this stage before they become active again, because even though they will probably move off slowly to find somewhere to hide, they can also disappear remarkably quickly, which can be incredibly frustrating if you're trying to photograph them. Although it will seem somewhat counterproductive at the time when you're struggling to see them, remember that they live in the dark, so try to keep your shadow over them if you can as they will definitely react if exposed to sunlight. I mentioned their first line of defence, but the second is that they have a reverse gear that can rapidly propel them backwards if they feel threatened, often flipping themselves through 180 degrees at the same time. It's the quickest exit you'll ever see - there one minute, gone the next.

Many people have never seen one of these fascinating creatures, but with a bit of patience they can be found. And, for what it's worth, it becomes easier once you've seen your first individual as you then have a much better appreciation of their size.

Our largest species, Dendrochernes cyrneus [Large tree chernes] may well grow to around 4mm, but they're very rare and only found in a few locations. The species you're more likely to see will typically have a body length of around 1.5 - 3mm, but identifying the ones to target is another matter as rather a large number are either rarely recorded or have only been found in certain areas of the country.

It all depends where you live, but unless you specifically want to look for species such as Pselaphochernes scorpioides [Compost chernes] which is primarily associated with decaying organic matter, or Allochernes powelli [Powell's chernes] for example which is only likely to be found in barn and stable refuse, your focus will probably be limited to a handful of species.

Obviously, some areas of the country will fare better than others, which is why I always like to do as much research as I can checking local distribution records before making any assumptions. And I'm glad I did, as I believe that within my local area

of East Dorset and the New Forest there are probably only five ground-dwelling pseudoscorpions that I could find in typical woodland habitat, plus a further two arboreal species if I was to start looking under bark.

I hope to be able to find all of these at some point, but at present I can only feature the species detailed below.

Bearing in mind that I've only photographed around 20-25 different individuals the situation may change but, at the moment, the most common species I've encountered is Chthonius ischnocheles [Common chthonid], which I've found at a couple of local woodland sites as well as in the garden.

This species is in the Chthoniidae family, characterised in part by having particularly large jaws (chelicerae) that are typically more than two-thirds the length of the cephalothorax.

The sexes vary in terms of size, with the females having a body length averaging 2.5mm, whereas the males are only 1.6mm. Cephalothorax brownish olive-green, chelicerae and pedipalps reddish to reddish-brown; abdomen reddish-brown with an undivided single dorsal plate; palpal hand with long, slender fingers; two pairs of large eyes.

Widespread and locally common, primarily found in woodland soil and litter, but also under stones and other ground laying debris.

I've also had quite a bit of success in finding the closely related Chthonius tenuis [Dark-clawed chthonid] and on at least

two occasions have found three or more of this species on the same piece of deadwood. Most of the sightings have been in Ringwood Forest which is mainly dry coniferous woodland, but I've also found a couple of individuals at one of my favourite sites in the New Forest which is open broadleaved, predominantly oak and beech, woodland.

Chthonius tenuis is in the same genus as the previous species so obviously shares the same characteristic feature of the family by having noticeably large jaws.

The females have a body length of around 2.3mm, and the males are around 1.3mm, so rather small, which is why I'm pretty pleased with some of these photos. Cephalothorax dark olive-green, chelicerae and pedipalps reddish-pink apart from the palpal hand which is distinctly darker, much the same colour as the cephalothorax; fingers long and slender; abdomen usually darker and rather glossy; legs pale and pinkish; two pairs of eyes.

Widespread across southern England and Wales, prefers drier habitats and more likely to be found hidden under stones and deadwood than in litter.

Unfortunately, I haven't had much luck though with our most widespread species Neobisium carcinoides [Moss neobisid] which, together with the Common chthonid, account for around 60% of all the Pseudoscorpion records on the NBN Atlas, although interestingly that's not quite the situation locally as in Dorset (VC9) and South Hampshire (VC11) combined it's more like 40% but, even so, it's a high percentage. At present, I've only seen this species at two locations, Horton Wood and in Ringwood Forest, both of which are primarily coniferous woodland.

This species is in the Neobisiidae family, characterised in part by having small jaws that are typically around half the length of the cephalothorax - see the comparison photos below showing Neobisium carcinoides alongside Chthonius ischnocheles.

The body length averages 2.2 to 3mm, with the sexes best determined by checking the genital area. Cephalothorax and abdomen concolourous, dark brownish-olive; pedipalps reddish or reddish-brown; legs pale brown; two pairs of eyes.

Common in all areas and occurring in pretty much any habitat, living in leaf-litter, decaying vegetation or among mosses, under stones and deadwood.

The two remaining species that I've identified, but have not yet seen are Roncus lubricus [Reddish two-eyed chelifer] which, like the Dark-clawed chthonid, favours drier litter. The second is its close relative Roncocreagris cambridgei [Cambridge's two-eyed chelifer] which again favours dry deciduous woodland litter. I initially thought this particular species was out of area, but it appears to be a possibility especially in coastal locations.

All five of these listed species are more likely to be found on the ground in litter or beneath stones or, certainly in respect of most of the individuals featured here, on the underside of lying deadwood.

If I took some time looking under bark on dead or very mature trees, I might be able to find Chernes cimicoides [Common tree chernes] or, although far less likely, possibly Allochernes wideri [Wider's tree chernes]. And, because I'm not sure of the identity of the individual featured below, which I initially assumed was a juvenile Chernes cimicoides, I shall also add the previously mentioned Pselaphochernes scorpioides [Compost chernes] to this small group as it has occasionally been recorded from woodland leaf-litter and deadwood even though it's predominantly associated with decaying organic matter.

Pselaphochernes cf.scorpioides and Proteriulus fuscus

< as noted, this individual is undefined, but it could possibly be Pselaphochernes scorpioides (averages 1.5 - 2mm)

Found in the company of the tiny millipede species Proteroiulus fuscus which measures no more than 10-12mm long and, therefore, provides a very good indication of size.

Members of the Chernetidae family are characterised in part by having a divided dorsal shield and no apparent eyes.

The most likely species to find will be Chernes cimicoides [Common tree chernes]

They have a body length averaging 2.2 to 2.7mm. Cephalothorax reddish olive-brown; pedipalps reddish tawny-brown; abdomen dull, dark yellow brown.

Widespread, occurring in woodland, beneath bark and in rotting wood, preferring dry, dead standing or fallen trees, but also a possibility on larger branches laying on the ground, and on over-mature trees, particularly oak, beech, elm and willow.

The final species that could possibly be found beneath bark on old and dying trees, especially aspen, but also beech and birch, is Lamprochernes chyzeri [Chyzer's shining claw] which is slightly smaller than Chernes cimicoides with an average body length of just 1.8 to 2mm. It can be easily confused with Lamprochernes nodosus [Knotty shining claw], but has marginally larger palpal femora and tibia. I think it's very unlikely that I'm going to find either of these, but they have been recorded locally, albeit very rarely.

Whilst I do not 'collect' species as such, I do occasionally sift litter when I'm out, particularly during the winter months when

I'm having to search for species to photograph. I wouldn't normally take photos on white backgrounds or in collecting trays, but coincidently I did find a couple of shots of our two most common pseudoscorpions Chthonius ischnocheles (left) and Neobisium carcinoides (right) which provide a useful side by side comparison.

Apart from the colour of their body and legs which can be variable, note the relative size of the jaws, which are far more pronounced in Chthonius ischnocheles, but also the difference in the size and shape of the palpal hand and fingers (pincers).

Created Aug.25 | updated - (v.1)