ACARI | Oribatida

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Following on from the general introduction to Oribatida on the previous page, all of the species / genera I'm currently able to feature are represented here in their systematic (hierarchal alphabetic) order in accordance with the official listing used on the Soil Biodiversity UK website. Each family includes a 'header' confirming the full taxonomic classification.

ACARIFORMES > Sarcoptiformes > Oribatida

Desmonomata (=Desmonomatides) > Brachypylina > Poronoticae > Ceratozetoidea > Euzetidae

It's rather appropriate that the first species featured here is Euzetes globulus as it's regularly credited as being one of the most photographed oribatid mites due to its size and shiny appearance that apparently makes it stand out, and the fact that they're supposedly very common.

I'm not sure I'd agree with either of those two reasons because, even if they are common, which I would question, I wouldn't say that they're particularly easy to find despite being in the region of 1-1.2mm long. That might be considered large for a mite, but they're still tiny. Yes, they're shiny, which does make them easier to spot, but the downside of having a hard reflective surface is that they're tricky to photograph with flash. It's fine to have a bit of a highlight, but not a large blown-out patch. You need low flash power, a good diffuser and the right angle and, dare I say, you also need to see them on deadwood or in litter rather than on the ground as you'll struggle to get a decent shot of any dark-coloured mite on soil.

They have a certain look about them that has resulted in various common names, such as the 'black helmet mite' which is a pretty good description, except that that they're not actually black, but rather very dark brown. If you find an individual that's more of a reddish-brown colour it's either freshly moulted or possibly another species. The front rim of the 'helmet' has a distinctive shape and the pronotum, which has a pair of lamellae with setae arising from the ends of free cusps, is rather short and barely visible when viewed from above.

Euzetes globulus is the sole member of the Euzetidae family.

Location / habitat notes: A few different individual featured, photographed at various local sites including Garston Wood (ancient coppiced woodland) on the ground under an old cut log, at South Oakley in the New Forest (mixed woodland)

on decaying deadwood, and from our front garden retrieved from soil under weed-control membrane.

ACARIFORMES > Sarcoptiformes > Oribatida

Desmonomata (=Desmonomatides) > Brachypylina > Poronoticae > Ceratozetoidea > Humerobitidae

Humerobates rostrolamellatus is a medium-sized, 700-850µm long, reddish brown mite, which has a heavily-sclerotized, smoothly rounded, oval body with well-developed lobe-shaped pteromorphs that have a visible hinge line, and with the front pair of legs emerging from behind a protective flange known as a pedotecta. The pronotum lacks a translamellar, but it does have a pair of prolamellar that are longitudinal ridges that run down the lateral margins of the rostrum. The interlamellar setae are very long and straight.

It is a member of the Ceratozetoidea and, in a similar position as the previous species, is the sole British representative of its family, the Humerobatidae. It is a widespread arboreal mite that in some areas is strongly associated with certain types of fruit trees, but also occurs on various broadleaved trees especially in more open, drier locations where it lives on the bark or amongst mosses and lichen feeding on algae and fungi.

Location / habitat notes: The individual featured here was slightly the larger of three of these mites that I found on a large fallen branch in a lightly wooded area of otherwise open wood pasture at Half Moon Common in the New Forest.

ACARIFORMES > Sarcoptiformes > Oribatida

Desmonomata (=Desmonomatides) > Brachypylina > Poronoticae > Galumnoidea > Galumnidae

Although the Galumnidae family only includes eight species in four genera, Acrogalumna (1), Galumna (4), Pergaluma (2) and Pilogalumna (1), they are so similar in appearance that even the genus, let alone the species, cannot be identified from photos with any level of certainty.

They have a relatively smooth, well-rounded body coupled with a shortish triangular-shaped prodorsum with a rounded rostrum, but the primary distinguishing feature is the notably large pteromorphs that extend much further forward than backward from their point of attachment. These bilobed or auriculate ('ear-like') shields which help to protect the mite's legs are quite variable in form from one family to another and, whereas in species such as Euzetes globulus that have fixed pteromorphs which are continuous with the body and barely noticeable, in the Galumnidae they are movable and particularly well-developed. Another feature of the galumnid pteromorphs, although very difficult to see in photos, is that they have an 'alary furrow' or 'pseudo-fissure' (effectively a short bright stripe) located in the middle just below the hinge line.

The prodorsum lacks true lamellae, but may have carina, or narrow lamellar or sub-lamellar ridges that, in combination with the arrangement of the notogastral pores and certain setae, need to be carefully examined to determine the genus and subsequently the species.

They have an overall body length averaging around 550-700µm, apart from Acrogalumna longipluna which is a tad larger at 625-800µm, and Galumna obvia which can be up to 850µm. Obviously, you can't gauge the size in the field, but I'm still of the view that, certainly with the equipment I use, 700µm is just about the smallest size that can be realistically photographed with any level of detail. It's purely an observation, but it's a point worth remembering when checking photos and looking at the possible candidates as some of the smaller species can probably be discounted. I also think that regardless of the previous comments about identification, the general shape and amount of forward projection of the pteromorphs when viewed from above may suggest a possible species!

Location / habitat notes: The individual in the first two photos was a lucky find on damp leaf-litter that had been collected from our front garden and, although I've looked numerous times since, I haven't found another. In fact, the one featured in the other two photos is only the second one that I've managed to find. I spotted that one in Ringwood Forest on a small piece of deadwood along with a few other oribatid species but as far I could see it was the only galumnid.

ACARIFORMES > Sarcoptiformes > Oribatida

Desmonomata (=Desmonomatides) > Brachypylina > Poronoticae > Oribatelloidea > Achipteriidae

The Achipteriidae family includes twelve species in four genera, which are broadly distinguished by having a prodorsum

with lamellae that are either closely adjacent, fused medially and/or linked with well-developed translamella, and a notogaster that includes fixed pteromorphs bearing forward-pointing prongs.

As far as I can ascertain, the individual currently featured here is Achipteria nitens, which is a tad larger than the more common species Achipteria coleoptera, at 600-800µm with a slightly more elongate shape and with much longer notogastral setae. Otherwise described as dark brown, sometimes yellowish, with a smooth, rounded body; notogaster longer than wide with minute granular cerotegument (waxy covering); pteromorphs with a knife-like tip; rostrum pointed when viewed both dorsally and laterally; lamellae fused medially, but with the cusps well separated; interlamellar setae long and thin; rostral setae long and extending beyond the tip of the rostrum.

Location / habitat notes: Three individuals featured that were photographed at different times in different areas of Ringwood Forest (dry coniferous woodland), all solitary, and all found on small pieces of fallen deadwood.

ACARIFORMES > Sarcoptiformes > Oribatida

Desmonomata (=Desmonomatides) > Brachypylina > Poronoticae > Oribatelloidea > Oribatellidae

The Oribatellidae family (not to be confused with the similarly named Oribatulidae) is only represented in Britain by six species which are taxonomically placed alongside Achipteriidae within the Oribatelloidea, whereas in larger systems the Achipteriidae is often separated within its own superfamily Achipterioidea.

All of these species have broad lamellae that cover most of the prodorsum, but in Oribatellidae the cusps are particularly large and may be fused at the base as they are in Ophidiotrichus tectus, or converging with either a single pair of teeth as with Joelia fioril or consisting of an inner and outer pair as present in the four Oribatella species. The pteromorphs are immovable and the notogaster has 10 to 14 pairs of short to long setae.

Oribatella is further defined by having a longer prodorsum, which is around half the length of the notogaster, raised lamellar and the notogaster with well-developed porous areas. Oribatella calcarata is the larger of the four species, averaging 600-700µm, whereas Oribatella litoralis is only around 450µm, and Oribatella berlesei and quadricornuta little more than 500µm.

It is also a distinctive dark reddish-brown to blackish-brown colour with the lamellar slightly separated rather than overlapping as in quadricornuta and with the tip of the inner cusp invariably being very slightly longer than the outer tooth when viewed from directly above.

Location / habitat notes: At present, this is the only individual I've seen - found on a relatively small piece of deadwood at Barrow Moor (primarily Beech and Oak open woodland) in the New Forest.

ACARIFORMES > Sarcoptiformes > Oribatida

Desmonomata (=Desmonomatides) > Brachypylina > Poronoticae > Oripodoidea > Oribatulidae

Oribatulidae includes 15 species in three genera, Oribatula, Phauloppia and Zygoribatula but, as far as I can ascertain, the only member of the family that you're likely to find and be able to photograph is probably Phauloppia lucorum. It's the largest species at around 600-900µm and is reasonably easy to distinguish; having a brown body comprising a well-rounded, finely punctured notogaster covered with fourteen pairs of long, slightly curved setae, and a pronounced prodorsum that has very thin, barely discernable, centrally located lamellae, and short sensillus. They're an arboreal mite, particularly associated with lichens and decaying mosses on trees.

Phauloppia nemoralis and rauschenensis are smaller (>600µm) and have shorter body setae, while Phauloppia pilosa is smaller still (>500µm) with much longer setae.

[Phauloppia lucorum is often cited alongside Lucoppia burrowsi, a similar species that occurs in Europe. It's not listed as being recorded in Britain, but I have seen it mentioned, so whether it's possibly a new species I'm not sure. Alternatively, it

may just be a synonym of another species given that Phauloppia lucorum was formerly named Lucoppia lucorum].

Location / habitat notes: Photographed at a couple of locations in the New Forest (damp and dry woodland), found on decaying deadwood lying in leaf-litter.

Whilst I'm starting to learn a lot more about oribatid mites in general and now feel reasonably confident in identifying certain species, there are some families that are always going to prove difficult and Oribatulidae is certainly one of those. The following individual looks as though it should be represented here and, if so, it could possibly be one of the five Oribatula species, most likely Oribatula tibialis. But, that's no more than a tentative suggestion as there's simply no way of being sure. Unlike Phauloppia, the Oribatula genus have well-developed lamellae that broaden towards the tip. They also lack trans-lamellae and have four pairs of porose areas on the notogaster, which can only be verified with close examination. On that basis alone, this individual is 'undetermined' but, all the same, I thought it was useful to include the photos as a reminder of when to step back and accept that even if a species is just about photographable it doesn't mean that it can be identified or even confidently allocated to a family!

Location / habitat notes: Ringwood Forest (dry coniferous woodland) on moss and algae-covered rotting deadwood.

ACARIFORMES > Sarcoptiformes > Oribatida

Desmonomata (=Desmonomatides) > Brachypylina > Poronoticae > Phenopelopoidea > Phenopeiopidae

The Phenopelopidae family includes 14 species in two genera, that are distinguished in part by having a rounded body with the notogaster mostly covered in a thick, rather granular, waxy cerotegument (often with attached debris), with a variably sized, longitudinal clear spot (lenticulus) anteriorly; and well-developed pteromorphs. The front edge of the notogaster may either have a small projecting ridge known as the tectum that covers the insertion point of the interlamellar setae which are expanded and flattened into long, transparent, leaf-like (phylliform) shapes, being a characteristic feature of the genus Eupelops; or with the anterior border projecting less than the front extension of the pteromorphs, and with the interlamellar setae being small and thin, which are features associated with Peloptulus montanus and Peloptulus phaenotus [small species averaging 500µm or less].

Although the remaining twelve species are listed in the Eupelops genus only nine appear to be properly described and, when you start doing a bit more research, there are probably only five that really need to be considered from a photographer's perspective. The official 'key' splits Eupelops into two groups based on the proximity of notogastral setae lp and h3. The two species of interest where these setae are closely located are Eupelops clavinger [650-750µm] and Eupelops torulosus [600-800µm]. The others in the size range that should be photographable have these setae far more widely spaced. They are Euelops plicatus [500-680m] that could still be a little on the small size, Eupelops acromios [600-840µm], and the largest member of the genus Eupelops hirtus [850-1100µm] which can be easily distinguished by its size and very long notogastral setae.

I'd previously only had one brief encounter with one of these species and the resultant photos were poor and were only included here as 'record shots' so I'm pleased that I subsequently found five individuals on the rim of our garden waste bin. They provided much better photo opportunities which are probably as good as I'm likely to manage for species of this size. I'm pretty sure they're Euelops acromios based on the form and arrangement of the notogastral setae and a couple of other features such as the shape and projection of the tectum and the well rounded pteromorphs.

ACARIFORMES > Sarcoptiformes > Oribatida

Desmonomata (=Desmonomatides) > Brachypylina > Pycnonoticae > Carabodoidea > Carabodidae

Before having a look at the next couple of families, I think that for anyone who hasn't actually tried photographing them it's worth pointing out that they really are tiny and, unless your eyesight is a lot better than mine, they're just tiny black dots until you focus on them. You're never quite sure what you've found until you look through the viewfinder but, to me at least, that's part of the attraction as you're discovering and trying to photograph species that are effectively invisible to the naked eye. Obviously, that applies to most oribatid species, but particularly so in respect of these families.

The Carabodidae family comprises 14 species in two genera, Carabodes and Odontocepheus, with all but one of those species in the former. Although, Odontocepheus elongatus can be distinguished from its elongated body shape and the

four long, forward-pointing setae on the front edge of the notogaster, trying to determine the various Carabodes species is

far more difficult and, in theory, not reliably possible from photos.

They are variable in both size and appearance when viewed closely, but can all be characterised by their large and broad pronotum that is typically about half the length of the notogaster, with a rounded rostrum and wide lamellae with lamellar cusps. Their chunky body form gives the impression that they're relatively large by mite standards, but they're not. They're typically around 500-700µm long, but some species are as small as 300µm. Identifying the actual species requires close examination of the sculpturing of the notogaster and in some cases, the pronotum, coupled with the distribution and form of the notogastral setae.

If these species had antennae and eyes, they could be mistaken for tiny, black carabid ground beetles, hence the scientific names Carabus, and here Carabodes, derived from the Greek 'karabos', which means beetle, but with the added 'odes' suffix, to confirm the similarity.

They can often be found on rotting deadwood in the company of other species, especially Cepheus as featured below, but also on mosses and lichens growing on trees. I've also found them in relatively large numbers feeding on wood fungi.

Odontocepheus elongatus

Carabodes sp. - likely Carabodes rugosior

Carabodes sp. - likely Carabodes coriaceus

Carabodes sp. - likely Carabodes reticulatus

Odontocepheus elongatus

Although I appreciate that you can't expect to identify species this small from details captured in a photograph of a live individual taken in the field, you can certainly see the different sculpturing and, with a bit of time spent reading through the keys and descriptions, you can usually come up with a likely candidate. The biggest problem I've found is that the information available doesn't cover all the British species so has to be pieced together from a number of sources that use different terminology, plus the fact that the best key is in German, which isn't the easiest language to accurately translate.

The other factor, is that records are almost non-existent so it's exceptionally difficult to get an indication regarding the species that are likely to be seen but focusing purely on the larger species in the 600-750µm size range, I believe that there are probably only four that need to be considered:

Carabodes coriaceus - 565-725µm; prodorsum with a wide 'neck cavity' (dorsosejugal groove), in front of which are a pair of elevated humps; central area of notogaster with strong, irregular, tuberculate ridges; notogastral setae quite long and distally widened, but with the posterior marginal setae much shorter and usually difficult to make out in photos.

Carabodes reticulatus - 650-750µm; prodorsum with a conspicuous deep 'neck cavity' and thick interlamellar setae; central area of the notogaster with tubercles forming a contiguous mesh-like networked pattern; notogastral setae prominent, medium length and distally widened and, subject to angle, lighting etc., all ten pairs, including those around the posterior margin, should all be visible in photos.

Carabodes femoralis - 600-715µm; prodorsum shallowly sunk at the back, but without a 'neck cavity'; central area of notogaster with several course, irregular longitudinal ribs that are covered with small raised tubercles; notogastral setae very short and unlikely to be picked up in photos.

Carabodes rugosior - 520-650µm; prodorsum with pronounced raised nodules, and a flat recess at the back rather than an actual 'neck cavity'; notogaster with a prominent longitudinal central rib and irregular ridges to either side; ten pairs of short notogastral bristles including one on each shoulder, that are often barely visible in photos.

Each of these species has a couple of features that should make them relatively easy to distinguish but, in isolation, it can be tricky and also confusing, as it's not unusual to find two different species within the same group. The following photo isn't great as it's been heavily cropped, but the difference in the notogastral sculpture and the visible setae is obvious and, although, both of these species have a very conspicuous 'neck cavity' they are clearly different. However, they're also both featured here on their own prior to this coming together and, at a quick glance, you'd be forgiven for thinking they were the same species.

Carabodes cf.reticulatus and Carabodes cf.coriaceus (see text above)

Carabodes cf.reticulatus (see text below)

The photo on the right shows the deep 'neck cavity', the prominent thick interlamellar setae, most of the notogastral setae and the mesh-like sculpturing, which are all features of Carabodes reticulatus.

I don't believe that I've come across Carobodes femoralis as yet but, if my interpretation of the key features of these particular species are correct, the other three are represented as confirmed by the photo captions. But they must be taken as tentative suggestions as there are a further nine species and, although I'm reasonably sure that these are the four primary contenders, others such as Carabodes affinis, labyrinthicus and marginatus particularly may be encountered. They are smaller, generally in the region of 400-500µm and, in my view, barely of a size that can be seen, let alone photographed. Similarly, with Carabodes willmannii, which is often collected from moss, but is even smaller.

Location / habitat notes: Odontocepheus elongatus - Ringwood Forest (dry coniferous woodland), encountered a few times on small pieces of lying deadwood - sometimes solitary, other times in small numbers - but I've never found Carabodes sp.

in this habitat. Carabodes rugosior photographed at Brockishill (damp woodland) on wood fungi and also at Barrow Moor

(open broadleaved woodland) in the New Forest on an old fallen tree trunk. I've also found Carabodes reticulatus

and Carabodes coriaceus at Barrow Moor, but on rotting deadwood lying in leaf-litter.

ACARIFORMES > Sarcoptiformes > Oribatida

Desmonomata (=Desmonomatides) > Brachypylina > Pycnonoticae > Cepheoidea > Cepheidae

Cepheidae is in its own superfamily Cepheoidea. There are only eight species, but they're spread across five genera; Cepheus, Conoppia, Ommatocepheus, Protocephus and Tritegeus. With the exception of Conoppia palmicinta, which is more rounded with a near enough smooth notogaster, the remaining species are broadly distinguished by having a well-defined dividing line between the prodorsum and notogaster, and a body that has knobbly or densely networked sculpturing on the dorsal surface or rough sculpturing restricted to the sides.

The Cepheus genus includes four superficially similar reddish-brown species that have an almost round, slightly flattened, strongly sculptured notogaster with an edge border, which is typically very dark-brown, near black, in colour, but occasionally much more reddish. The rostrum is covered by large lamellae with the cusps either closely aligned or slightly separated. They are easy to recognise, but can only be identified to species with close examination of the sculpturing and the lamellar cusps.

Cepheus cepheiformes appears to be the more common form, and the 'type species' of the genus that is usually cited when referring to the very distinctive juveniles which carry the exuviae of proceeding moults on their back, best seen at the deutonymph stage as they have both the larvae and protonymph remains radiating out in a leaf-like pattern. They are only 400-600µm long and pretty much colourless and consequently, near impossible to see with the naked eye.

Fortunately, the adults are a tad larger averaging around 600-750µm long and 400-500µm wide. You'll most likely find them in woodland and forest clearings on fallen, rotting deadwood often in the company of other mites. They are slow moving, incredibly difficult to spot on dark wood and, in my opinion, an absolute bugger to photograph.

Having spent some time looking at the different sculpturing and trying to work out whether I've managed to photograph any

of the less common forms, it's worth making a note of the the important distinguishing features:

Cepheus cepheiformis - 520-740µm; lamellar cusps well-developed, and closely aligned; interlamellar setae strong; notogaster sculpture consists of dark, net-like connected ridges with elongated irregular pits between.

Cepheus latus - 670-900µm; lamellar cusps more rounded at the front and clearly separated; interlamellar setae bristle-like; notogaster sculpture has dark irregular ridges that are noticeably isolated from each other.

Cepheus tuberculosus - 640-745µm; lamellar cusps quite widely separated; interlamellar setae stiffly bristle-like; notogaster sculpture tuberculate, consisting solitary nodes in the central area and radial ribs on the lateral margins; lamellar and shoulder corners with a mesh structure; notogastral setae strong, distally thickened and partly projecting beyond the margin.

Cepheus dentatus 750-840µm; similar to Cepheus latus in many respects, except that the lamellar are angular (toothed),

and the notogaster sculpture consists of larger isolated net-like ridges.

Cepheus sp. - different colour form or different species to the others?

Cepheus sp. - almost certainly Cepheus tuberculosus

Location / habitat notes: Photographed at various locations in the New Forest (broadleaved woodland) and from some other local woodland sites, but also in Ringwood Forest (dry coniferous woodland) - nearly always found on relatively small pieces of fallen deadwood, and very often together with other oribatid species, particularly Carabodes and Hermanniella.

ACARIFORMES > Sarcoptiformes > Oribatida

Desmonomata (=Desmonomatides) > Brachypylina > Pycnonoticae > Cymbaeremoidea > Cymbaeremaeidae

Cymbaeremaeidae comprises a single, easily recognisable species Cymbaeremaeus cymba, which is around 700-800µm long with an oval brownish-grey body that one well-known acarologist describes as looking like a "flat-topped raisin with a wrinkly face".

It is placed within the Cymbaeremoidea superfamily together with another small family Micreremidae with just two species.

It is most often found on trees amongst moss or lichens, but my encounters to date are where I've found an individual within

a mixed community of other mites including the two previously mentioned species.

Location / habitat notes: My few sightings of this particular species have all been in the New Forest at Barrow Moor on reasonably largish pieces of dry deadwood.

ACARIFORMES > Sarcoptiformes > Oribatida

Desmonomata (=Desmonomatides) > Brachypylina > Pycnonoticae > Damaeoidea > Damaeidae

Oribatid mites have many different body forms, but none look like the typical members of this family that you find crawling through leaf-litter or over rotting deadwood on their long, rather spindly legs. Although somewhat variable in size and general appearance to some degree, they're pretty much unmistakeable. The notogaster is well rounded, almost globular, and is well differentiated from the triangular-shaped prodorsum. They're generally dark-coloured in varying shades of brown or grey, to almost black. Smaller species tend to be lighter, but they shouldn't be confused with the many nymphs you'll regularly come across.

The Damaeidae family is represented in Britain by 16 species that are usually placed in eight genera or, sometimes, in a lesser number with sub-genera. They can't be specifically identified without sticking them under a microscope and pain- stakingly counting setae on certain parts of the legs and checking whether they have tiny spines on the front edge of the notogaster, so the common practice, it seems, is to simply refer to photographed individuals as Damaeus / Belba sp.

They are the two primary genera with the others having names such as Epidameous, Kunstidameous or Damaeobelba, Metabelba etc., which I suspect are alternatively regarded as subgenera.

As a consequence of their diet compared with their predacious relatives, most oribatids grow slowly and take a relatively long time to fully develop, which leaves the nymphs particularly at risk of being attacked and eaten as their protective exoskeleton is shed between growth stages. Not to be outdone by the various defence mechanisms that the adults have developed in addition to the protection given by their body plates, such as having pteromorphs to shield their legs or the ability to roll up, nymphs of a number of species, but particularly members of this family, have their own strategy as they are often seen wearing their moulted body parts as armour. It looks bizarre, but it's remarkably effective as it provides a degree of protection as well as acting as camouflage and making the nymph look much larger than it is. Some adults also adopt this tactic by using various bits of debris.

Location / habitat notes: Although I've probably found this species on virtually every occasion I've been out specifically looking for mites, it's interesting to note that for some reason I haven't photographed that many in the New Forest; the individuals currently featured here were photographed in Ringwood Forest (dry coniferous woodland), White Sheet Plantation (mixed woodland) which is on the edge of Holt Heath, Spearywell Wood, Nr. Romsey (mixed woodland), Kitt's Grave (open broadleaved woodland), Garston Wood (coppiced woodland) and Redman's Hill (local mixed woodland) - all on various pieces of mainly rotting deadwood, some dry and some very wet as can be seen, dependant on the time of year.

ACARIFORMES > Sarcoptiformes > Oribatida

Desmonomata (=Desmonomatides) > Brachypylina > Pycnonoticae > Gustavioidea > Liacaridae

Liacaridae includes nine species in four genera, which are characterised in part by having a well-rounded, smooth body form with a small, somewhat pointed prodorsum with converging lamellae that, in respect of the species currently featured here, are fused apically.

The primary genus Liacarus has an unusually high level of variability between individuals, both in terms of size and formation of the lamellae. The variance in size can make you think that you're looking at different species, but fortunately the four different forms that can be found in the UK can be distinguished without too much difficult from features that should be visible in photos.

Liacarus subterraneus [800-1200µm] can be separated from the others simply by its almost circular, rather than ovoid, shape. The notogaster is very shiny and highly water repellent.

Liacarus cf.subterraneus

Location / habitat notes: Photographed at Brockishill, New Forest (broadleaved woodland).

Liacarus nitens [variable, up to 1200µm] is characterised by narrowly fused lamellae bearing small, almost cylindrical cusps with the lamellar setae inserted apically, and with a long, sharply pointed intercuspidal mucro, which usually projects beyond the cusps; front of rostrum with a pair of rounded notches.

Liacarus xylariae [750-1100µm] has broad lamellae that are widely fused at the front, with the lamellar setae inserted apically on small cylindrical cusps. Liacarus coracinus [650-1100µm] differs by having blade-like lamellae that are barely connected at the front, with the cusps always with a medial (inner) tooth that is larger than the lateral (outer) smaller tooth if present and usually, but not always, with a further unpaired small intercuspidal tooth. The lamellar surface is striated, and the interlamellar area between is clearly triangular (as can be seen in the following photos), whereas in Liacarus xylariae it's far shallower as the lamellar are much wider. The front of the rostrum has small rounded notches (difficult to see), but nowhere near as defined as in Liacarus nitens.

Liacarus coracinus

Location / habitat notes: Photographed at Barrowmoor, New Forest (open broadleaved woodland).

A slightly smaller and darker species, Dorycranosus splendens [650-850µm] with long, spindle-shaped sensillus may also be found. It is superficially similar apart from having a dull, weakly sculptured notogaster, and unconnected lamellar cusps that are formed as a triangular tooth. There are also two, even smaller species Adoristes ovatus and Planoristes acuspidatus that I don't expect to record, which have well-separated lamellae.

Xenillus

We then have the two Xenillus species, Xenillus clypeator and Xenillus tegeocranus, which are rather nice mites to photograph as they are a tad larger than most of the other oribatids they often hang out with.

The more common species is Xenillus tegeocranus, which I thought could be distinguished quite easily as they are typically darker than Xenillus clypeator with the notogaster having a slightly rougher and duller texture. The pronotum also looks to have a slightly different shape with the lamellae wider spaced, although that's purely my interpretation, not an official feature of the species. Xenillus clypeator on the other hand has a different appearance to my eyes as the individuals I've seen have been much paler - distinctly mid-brown rather than dark brown - with the notogaster appearing shiny with a smoother texture. They also have shorter, slightly clubbed, sensillus, whereas in Xenillus tegeocraus they're noticeably longer, and never have any conspicuous interlamellar setae.

The problem, is that Xenillus tegeocranus does have interlamellar setae just in front of the dorsal transverse line between the prodorsum and the notogaster which, unlike the sensillus, is very difficult to capture in photos. Personally, I'm not too bothered as the general appearance alone should be sufficient, but it's an important distinguishing feature that would need to be visible for recording purposes.

Xenillus clypeator

Location / habitat notes: The above photos were taken at Barrow Moor (open broadleaved woodland), but I've also found the species in very similar habitat at two other New Forest locations, Eyeworth Wood and Bolderwood.

Xenillus tegeocranus

Location / habitat notes: Although my current encounters with Xenillus clypeator have all been in the New Forest, I've found Xenillus tegeocranus at most of the sites I've vistied. Apart from at Redman's Hill (local mixed woodland) where I've seen them a couple of times in small colonies, I think that most of the others have been pretty much solitary.

ACARIFORMES > Sarcoptiformes > Oribatida

Desmonomata (=Desmonomatides) > Brachypylina > Pycnonoticae > Gustavioidea > Peloppiidae

Closely allied to the Liacaridae, the Peloppiidae family is only represented in Britain by two species, Ceratoppia bipilis and Ceratoppia sexpilosa. They are around 700-900µm long with a reddish to dark-brown colouration, a notogaster that is shiny and rounded posteriorly, and a triangular projecting prodorsum bearing lamellae ridges that extend into long horns, tipped with setae. The sensillus are long, and the interlamellar bothridial setae are very long and bristly.

Although Ceratoppia bipilis (including associated subspecies) appears to be the common form, I believe that the individual featured here is Ceratoppia sexpilosa as it has three pairs of long, conspicuous posterior notogastral setae, whereas Ceratoppia bipilis only has two. Initially I wasn't sure that I was interpreting the arrangement correctly, but I've now seen a diagram showing the location of the additional pair at position h1 which are in addition to the lower pairs at p2 and p3. They are very clearly visible in at least one of these photos.

Unfortunately, my current experience of the species is limited to one short encounter when I found this particular specimen on the underside of a piece of deadwood in a dry, but seasonally wet, area of the New Forest. Despite its tiny size, it managed to scurry away and hide remarkably quickly, giving me very little time to react. Hopefully, I'll get another opportunity at some point, but at least these photos show the important distinguishing features noted above.

Location / habitat notes: Bolderwood, New Forest (open broadleaved woodland)

ACARIFORMES > Sarcoptiformes > Oribatida

Desmonomata (=Desmonomatides) > Brachypylina > Pycnonoticae > Hermannielloidea > Hermanniellidae

Meet Herman, a somewhat variable, but rather distinctive little mite that always seems to be on a mission. When I found my first colony of these foraging on a piece of deadwood, I assumed that there were two species due to quite a distinct colour difference with some of the paler individuals looked rather unkempt compared with their darker relatives.

Subsequent research quickly revealed that there are indeed two species on the British list, Hermanniella granulata and a much rarer form Hermanniella punctulata, so it's pretty safe to assume that they're all the common species. And the reason for the variable appearance is that the remains of the tritonymphal exuvia adheres very closely and takes a while to wear off, which explains why some individuals look as though they're moulting.

They average around 650-850µm long and, from my experience, are extremely difficult to photograph due to a combination of their size and that they're invariably on the move, which never seems to be in a straight line. You work out which way they're headed, then faff around getting in position and, as soon as you think you've acquired focus, they do a U-turn or head off in a completely different direction. But there's no denying the fact that Herman has got real character, so you just need to persevere despite the frustration.

I love their large bothridia that can easily be mistaken for a pair of goggle-eyes, which together with the very conspicuous interlamellar setae and the presence of projecting funnel-like lateral gland openings on the sides of the notogaster, set Herman apart from any of the other oribatid mites that I've seen.

Location / habitat notes: I come across this species at virtually every woodland site I visit, whether broadleaved or coniferous. They're nearly always in small colonies and very often with other oribatid mites, particularly Cepheus and Phthiracarus sp.

Although not currently represented here, it's important to note that the Hermanniella genus is in the Hermanniellidae family, which should not be confused with the Hermannia species in the Hermanniidae family.

ACARIFORMES > Sarcoptiformes > Oribatida

Desmonomata (=Desmonomatides) > Brachypylina > Pycnonoticae > Neoliodoidea > Neoliodidae

There are a number of oribatid species that either carry remnants of their nymphal scalps, or have deliberately adorned themselves with various bits of detritus to help disguise their true appearance, but the various members of this family have taken the art to whole new level. They are heavily sclerotized mites that bear concentric nymphal exuviae - the shed skins of their previous development stages. Adults will have the remains of the larval scalps on top followed, in theory, by the protonymphal, deutonymphal and tritonymphal scalps siting underneath; a bit like the growth rings on a tree, which gives a guide to their relative age. They're certainly different and, once seen, they're not likely to be misidentified unless you find a completely 'clean' individual on its own like the one pictured below.

The Neoliodidae family occurs in many areas of the world with over fifty species recorded that are placed in four genera; Neoliodes, Platyliodes, Poroliodes and Teleioliodes. In Britain we have three species although, as far as I can ascertain, only two are normally considered. The first is Neoliodes theleproctus, regarded as the 'type species' of the family, and the second is Poroliodes farinosus as featured here.

They are closely related to the Hermanniellidae and, from my limited experience, are often found in the company of Hermanniella granulata. Immature individuals are about the same size, certainly under a 1mm, but adults are significantly bigger, probably nearer to 1.5mm and, because of the 'package' they carry are one of the larger oribatids that you could hope to encounter. Neoliodes theleproctus is an arboreal species that appears to favour drier habitats. I'm not sure whether Poroliodes farinosus has the same ecology, but it's worth noting that all of the individuals I've seen to date have been found on very dry deadwood or pieces of bark laying on elevated ground in coniferous woodland.

Finally, and without wanting to make the classification of these species more complex than it already is, but it's worth mentioning that the family was historically known as Liodidae until it was noted that the type genus Liodes could be confused with the fungus beetle genus Leiodes.

Location / habitat notes: To date I've only see this particular species in Ringwood Forest (dry coniferous woodland)

ACARIFORMES > Sarcoptiformes > Oribatida

Desmonomata (=Desmonomatides) > Nothrina > Crotonioidea > Camisiidae

The Nothrina hyporder (cohort) includes 38 species in six families that are separated into two superfamilies, Crotonioidea comprising Camisiidae (14) and Nothridae (5) as featured here and in the following section, plus Malaconothridae (11), Mucronothridae (1) and Trhypochthoniidae (2) which I'm not likely to encounter as those species are, in essence, semi-aquatic; and the Nanhermannioidea which includes the single family Nanhermanniidae (5).

Although the key identification features of the Nothrina relate to fused coxae and details regarding the genital shields that are obviously impossible to determine when trying to photograph mites in their natural habitat, the representative species of the primary families can be visually distinguished to some degree.

The Camisiidae family includes three genera, Camisia (9), Heminothrus (1) and Playtynothrus (4). They are slow-moving mites that can often be seen covered in an encrusted layer of dirt and other bits of organic debris as a means of a camouflage.

Members of the Camisia genus range in size from just under 700µm [Camisia invenusta] to around 1200µm [Camisia biurus and Camisia biverrucata]. They are relatively easy to identify as, despite the variance in size and general appearance, the notogaster is more or less oblong-shaped with central ridges and lateral depressions. The size and form might suggest a species, which is the case here, as I believe that both of these individuals are likely to be Camisia horrida, described as body length 825 to 960µm; colour brown to grey-brown; notogaster with almost parallel sides; lateral margins with sparse hollows; two longitudinal chitinous ridges, almost parallel, but branching out towards the rear corners; surface covered with flat-rounded humps; indentation on posterior margin of variable shape.

Camisia sp. - likely Camisia horrida

Camisia sp. - likely Camisia horrida

The distinction and placement of species between the Heminothrus and Platynothrus genera is treated differently by some authors with the latter sometimes being used as a synonym. However, in the British classification system, Heminothrus targionii is the only validated species in that genus. The remaining four species in this group are Platynothrus peltifer and Platynothrus thori which are well described, and Platynothrus fluviatilis and Platynothus punctatus that are not mentioned in any of the literature I've seen.

Platynothrus peltifer is generally regarded as the 'type species' as it's found in many areas of the world and has been well-studied as an important decomposer of organic material. Although primarily found in damp forest soils and litter, they have been recorded from many other habitats including wetlands. In addition to the role it plays in recycling nutrients back into the soil it is also a favoured food source for various small insects and spiders, especially certain species of ants and beetles.

Described as, body length from around 800 to 1000µm; colour dark brown (almost black in some light); body noticeably broadening towards the rear; central part convex anteriorly, but somewhat hollowed posteriorly; two distinct longitudinal ridges run between pairs of central setae, with two further folds of thickened chitin that run outside of the ridges - one pair outside of the central setae, the other along the lateral margins; notogastral setae long; posterior setae p1, h1 and h2 with whip-like curved ends.

Platynothrus peltifer

Location / habitat notes: At the time of writing, I've only seen Camisia in the New Forest at Barrow Moor (open broadleaved woodland). I've also found Platynothrus peltifer at this location and in similar habitat elsewhere, but also in Ringwood Forest (coniferous woodland)

ACARIFORMES > Sarcoptiformes > Oribatida

Desmonomata (=Desmonomatides) > Nothrina > Crotonioidea > Nothridae

The Nothridae family is only represented in Britain by five species, which are all in the Nothrus genus. They bear some superficial resemblance to the previous group, but can be distinguished by the slightly more rounded notogaster that has a central raised area surrounded by shallow curved channels. Further selected characteristic features specifically relating to

the genus include a body surface with microsculpture; triangular-shaped prodorsum in dorsal view; sensilus long; 16 pairs of notogastral setae, with h2 and p1 occasionally longer.

Whereas the previously described Camisia are variable in form, these Nothrus species all have a rather similar body shape and appearance. However, they do vary quite a bit in term of size and also in respect of the length and arrangement of the notogastral setae.

In respect of size, the smallest species are Nothrus anauniensis and Nothrus silvestris that are both around 700-800µm, then Nothrus pratensis which is quite variable at 760-940µm, Nothrus borussicus at 900-1000µm, and finally the largest and broadest species, Nothrus palustris at 1000-1200µm.

Nothrus sp. - probably Nothrus silvestris

The individual featured here was certainly one of the smaller forms and is very probably Nothrus silvestris as that species is described as having a slim elongated body that is only slightly broadened posteriorly (more so in the other forms); prodorsum separated from the notogaster by a less sclerified region, otherwise covered in with round cavities; the median notogastral setae and h1 relatively long, slightly swollen distally; setae h2 very long and usually curved medially.

Members of the genus are regarded as general feeders on decaying plant matter and fungi.

Location / habitat notes: Photographed in Ringwood Forest (coniferous woodland)

ACARIFORMES > Sarcoptiformes > Oribatida

Mixonomata (=Mixonomatides) > Euptyctima > Phthiracaroidea > Phthiracaridae

The Mixonomata infraorder is split into two divisions; Dichosomata with four species of dichoid mites in three families, each within their own superfamily; and Euptyctima with 28 species of 'box mites' that have a ptychoid body form where the ventral plates are adapted such that the mite can withdraw their legs and, by deflating their rather soft podosoma, can fold themselves up into a fully protected ball by closing the opening with their aspis (prodorsum).

Euptyctima includes three families; Euphthiracaridae with four species in three genera and Oribotritiidae with just three species in two genera that are grouped together in their own superfamily, Euphthiracaroidea; and Phthiracaridae as featured here with twenty-one species in four genera, Atropacarus, Hoplophthiracarus, Phthiracarus and Steganacarus.

The largest genus is Phthiracarus with 14 recognised species, but regardless of their variable size and colour, they can't be specifically identified from photos as the distinguishing features primarily associated with the length and form of the sensillus and notogastral setae can only be properly assessed under a microscope.

The two most common species appear to be Phthiracarus affinis and Phthiracarus clavatus, which have an overall body length of 620-840µm and 900-1030µm respectively. It's interesting to note as I see the species quite a lot and generally ignore smaller individuals and would guess that most of those that I photograph are probably around 1mm or so when fully extended.

Because the podosoma can be withdrawn, the body size is separated - for example, Phthiracarus clavatus is described as having a notogaster of 620-700µm and a prodorsum of 280-330µm. The remaining species are rarely recorded from the information I've seen.

Phithiracarus sp.

You occasionally come across ptychoid mites that are rolled up in a position where you can see their underside. Similarly, if you see one that's fallen over and ended up on its back, which they seem to have a habit of doing. They soon flip themselves back over, but in both cases it's worth taking a few photos to check the ventral shields. In the Phthiracaridae family the genital shield is effectively fused to the adjoining anal shield forming a broad double pair of 'shutters', with the rear edge of the anal shield being rounded. If they're long and narrow, you need a closer look as it could be a member of the other families. In that respect, it's worth noting that the Phthiracaridae species typically have a relatively broad, well-rounded body, whereas members of the Euphthiracaridae and Oribotritiidae have a somewhat narrow anogenital region and a body that is distinctly laterally compressed.

Location / habitat notes: The above photos were taken at a couple of different locations in the New Forest and in local broad- leaved woodland, but I have seen the species at various other sites including in coniferous woodland.

Steganacarus

Last up we have the very distinctive Steganacarus magnus, which can measure up to 1.5mm when fully extended and is therefore, on average, probably the largest oribatid mite you're likely to see. Although Steganacarus magnus is the common 'type species', there are three other species in the genus, so it should only be labelled as such if the body setae are of similar size, sticking up on the top, and a bit more 'slicked back' on the sides, and you can see long hairs on the anal shield. You'll need a bit of luck to see the underside, like the individual featured here that had fallen over but, even though it was facing the wrong way, the hairs were still visible. That particular specimen was officially identified and, although I suspect that probably most of the others featured here are in fact the same species, I haven't captioned them as such.

Steganacarus magnus (confirmed)

I've seen no specific reference to their colour, so assume that it could be virtually any shade of brown. I won't read too much into the different colours that I've seen other than it might have something to do with the habitat and whether its exposed or shady, but I've photographed a lot of these species and have noticed that different populations tend to have a consistent colour between the individuals that can be pretty much defined as either tan-brown, reddish-brown or dark chestnut-brown.

Steganacarus sp.

Location / habitat notes: My only confirmed encounter with Steganacarus magnus was on the underside of a large log that

I'd rolled over at Blandford Lakes, near Ringwood. All of the other individuals that I've come across have been photographed on various bits of deadwood in various woodland locations.

Created April 25 | updated Aug.25 (v.5)