ALEOCHARINAE Fleming, 1821
POLYPHAGA Emery, 1886
STAPHYLINOIDEA Latreille, 1802
This group is currently acknowledged to be among the largest of the rove beetle subfamilies but, with the possible exceptions of the Nearctic and western Palaearctic faunas, it is also among the least well understood. There are no doubt countless new species to be discovered, and if ever this is achieved the group will become the largest by far; about 65000 species of Staphylinidae have been described and of these about 13000 are included in the present subfamily, this is about equal to the Pselaphinae, about twice as diverse as the Paederinae and the Staphylininae, and much more diverse than any of the other subfamilies. On the other hand it is also likely that certain groups will be removed from the Aleocharinae and that new subfamilies will be recognized, but as a guide to how things stand at present (2022) the group includes about 13000 species in about 1200 genera (in many cases very loosely assigned and based on historical literature), in up to 52 tribes and various other groupings. It is probably fair to say that no single classification is universally accepted and that any system is likely to change as new discoveries are made in exotic regions. Our UK fauna is among the better understood, mostly as a result of European research and publications, but it still represents great challenges for coleopterists at all levels and there is no modern (i.e. useful) guide to their identification. But there are some very fine guides freely available online which substantially cover the central and northern European fauna, including that of the UK, which translate well enough and are not too technical for those with reasonable experience of identification work. Many of these are based on various volumes the German work Die Käfer Mitteleuropas by Freude, Harde and Lohse but many other good works in Italian and French etc. are also available. These have been used by UK coleopterists for decades, and they have been the driving force behind many of the new species added to our list, but until recently they have only been available as a series of expensive volumes and then only with very difficult German texts. The much hoped for completion of the final volume of Beetles of Britain and Ireland by Andrew Duff should be a game-changer in this respect. In general it can be said that a fair number of our species are distinct enough to be identified from available works, even from Joy’s Handbook, but that the majority will need to be very carefully researched and usually dissected before any names can be assigned, and here a carefully named reference collection is invaluable. In many respects the group is not accessible to those who name and record things from photographs.
It is likely true to say that at least some aleocharine rove beetles occur in all habitats and that most of the commonly-worked habitats host a fairly diverse fauna. Sometimes they cannot be avoided e.g. working dung will usually produce Nehemitropia lividipennis and Aleochara lanuginosa, while sieving compost will often produce a wide variety of species, many of which are obviously different but destined to remain unidentified for the foreseeable future (we have thousands.) In terms of diversity the best habitat is decaying vegetation, especially where this is permanently damp e.g. compost or stored straw, followed by decaying fungi, carrion and dung, and most species tend to occur in large numbers at particular times of the year; sieving large and partly decayed terrestrial sporocarps in woodland habitats may yield thousands of specimens of a wide range of species. Many habitats will produce more specialized species, unfortunately alongside many of the common ones just to confuse them, these include wetland margins, dunes, open moorland, sphagnum bogs and upland meadows, many will be found in or about avian and mammal nests and It is among the very few groups of insects to adapt to and diversify in the intertidal zones of estuaries and beaches. Some will be found only under the bark or within decaying wood of old trees or fallen timber, some are adapted to live in other insect galleries and many are associated with social insect nests, especially those of ants and termites where many specific associations occur. A good overview of our myrmecophilous species is given in the Coleopterists Handbook. Many have become very specialized e.g. the eight known species of Tachiona Sharp, 1883 from Central America occur among webs in ghost moth (Lepidoptera, Hepialidae) galleries. Among our UK fauna species of Aleochara are parasites of diptera pupae, and the tiny Atheta scapularis (Sahlberg, C.R., 1831) is parasitic on Glow-worm pupae (Lampyris noctiluca). Most species are thought to be predators or, for at least part of their lives, parasites, but at least some are known to be exclusively mycophagous and it is likely that many are saprophagous or partly so. Many may opportunistically feed on pollen or nectar; beating blossom in the spring will often produce a range of species and often in abundance while sweeping flowers generally will produce adults through the warmer months. Some species of the Neotropical genus Amazoncharis Pace, 1990 are known to be significant pollinators of various palm trees. Adults of the Neotropical genus Charoxus Sharp, 1883 bore into unripe figs to lay eggs and the resulting larvae predate fig wasps, adults also predate emerging wasps and their seasonal abundance correlates with that of their host species, even on specific trees. This is intended to give some impression of the group but many more unusual specializations can be found on line. The biology of most species is completely unknown and while the seasonality and breeding habits of many can be inferred from collecting data, the actual bionomics are likely to be more complex than this might suggest. Sampling is simple, adults can be swept, beaten or sieved from many situations, many are nocturnal and some come to light or sap, they occur in pitfall and flight-interception traps and some are occasionally numerous in yellow-pan traps. carrion, dung, litter and flood-refuse are always worth sampling and extraction methods should be employed in all cases. Fungi, including subterranean species, should always be sampled, especially when the fruiting bodies have started to decay, and a wide range of species may be found and some e.g. species of Gyrophaena Mannerheim, 1830, are rarely found elsewhere.
Regarding identification, this is a very difficult subject; it requires great perseverance and represents a considerable test of character but the problems can be overcome and, as with any group, many genera and species will become familiar and identifiable on sight. Most of the tribes are in some sense accessible but the real problems are presented by the Athetini and, to a lesser degree, the Aleocharini, these are discussed below under the tribal headings but for now we try to characterize the subfamily as a whole. This discussion relates mostly to our UK fauna; this is relatively well understood and so this is how we define the group, but it is likely, especially as the faunas of other world regions are being consolidated, that it will prove to be inadequate in the wider view. Most species are small and many superficially resemble typical forms of other subfamilies e.g. the fusiform Tachyporinae or the parallel-sided and discontinuous form seen in many Oxytelinae or Paederinae, but here various features including, crucially, the placement of the antennae, will determine the group. Antennae filiform to gradually thickened from the base, without outstanding long setae to the basal segments. Antennae inserted on the dorsal surface of the head, the insertions clearly visible from above, outside the base of the mandibles and near the anterior margin of the eyes (this last character is generally good for the European fauna but many exotic forms differ). The head lacks ocelli and the pronotum is pubescent although sometimes sparsely so, and the elytra are not demarked by a border separating the dorsal surface from the reflexed lateral sides. The antennae are usually 11-segmented but the tribe Hypocyphtini is the exception, here it is 10-segmented which is handy because the antennal insertions are atypical. In general aleocharines are small beetles; most are 3-5 mm in length but a few reach 10 mm, many are smaller and some are less than 1 mm. Body shape varies enormously and most characters are also variable e.g., all tarsal formulae from 2-2-2 to 5-5-5 will be found. Most are drab in colour, from pale to dark brown or black, buy many are pale or have contrasting body segments, and some are have striking combinations of yellow, red and black. [The monophyly of the group has recently been established based on various larval characters and the structure of the large and multi-articulated lateral lobes of the aedeagus.]
Dissection is often necessary in Aleocharinae identification, making genitalia diagrams such as these of Aleochara curtula (above) and Autalia impressa (below) essential.
We now consider very briefly the tribes represented in the UK. These have traditionally been separated into groups according to the tarsal formula, a system that sometimes works and sometimes does not because in many cases the segments are very difficult to count, even at high magnifications, and mistakes which have assigned species to the wrong tribes have been made in the past. To the uninitiated this seems unlikely but be assured that it can be very difficult indeed, especially as the largest groups have either 4-5-5 or 4-4-5 tarsi, on the other hand many of those with 5-5-5 tarsi seem to be easy enough to see. In some cases a tribe may include species with different tarsal formulae e.g. the Aleocharini. It takes time. Joy gave two keys in his ‘Practical Handbook’; the first relied on distinguishing the tribes according to tarsal formula while the second (which is much more extensive and often feels like it was designed to drive the user insane) uses other morphological features. This second key is highly comparative and takes some considerable time to get the hang of but eventually many genera and species will become familiar, and just as many will remain a mystery. But Joy’s key can be worth the effort, especially nowadays with such good reference material online. A rather accidental test of Joy’s keys involves taking specimens that defy identification, dissecting out the genitalia and comparing these with figures such as those given in the plates by Strand & Vik. This can often provide a good identification, especially for female specimens which are generally easier to compare with the figures than males. Once identified they can be worked backwards in Joy’s keys and this often makes the keys to some degree sensible e.g. regarding the form of antennomeres or the relative proportions of various body segments etc. But whether this is worth the effort is a personal matter; it can become highly addictive and it is very time consuming but it will produce reliably named specimens and lots of coleoptery skills will be learned, especially how to produce decent dissections without any fuss and how to navigate the minefield of synonymy that is generated when using several works simultaneously. An extension of this is to find and catalogue genitalia figures from websites etc. Many of our species are figured somewhere or other and the dissections are usually very good, and when formatted a dozen or so to a page and printed out these are a very powerful tool for aleocharine idents. This is not the place for an in depth discussion about dissection but a brief summary, intended to give a feel for the subject, is given under the Athetini tribe below. Any discussion of this tribe would be incomplete without this but it also applies equally to other tribes and so any prospective student of the group will need to be very aware of the procedures.
This subfamily is very difficult to get to grips with, have no doubt about that, but by considering carefully each tribe individually it is possible to get a feel for many of the morphological ‘forms’. This approach will also make the difficult tribes a little easier by removing some of the similar species from other tribes. The best way to do this is to work through the tribes along with online keys such as those of Mike Hackston or Arved Lompe (the latter in German from Freude, Harde & Lohse, but which translate reasonably well via google) and adding more specialized papers along the way, all the while collecting pictures and constructing illustrated files of species and dissections. This will gradually allow sense to be made of the group. The worst thing to do is to consider the subfamily as a single entity, as Joy more or less did, because it is then too easy to get bogged-down in detail. As an example of this try using Joy’s keys with an obscure species of Athetini and see how that goes. On the other hand Joy was quite serious about using often highly comparative characters within a complete framework of the group (try key 2 from p.16.), and there are people who get along fine with this and produce good idents, but for most of us this wide approach becomes too ambiguous as there are too many couplets that might or might not lead us astray. Far better to treat each tribe as a case study and to gain a gradual familiarity of the subfamily. On the plus side there will be no shortage of specimens.
GYMNUSINI Heer, 1839
This small tribe includes 14 species of the genus Gymnusa Gravenhorst, 1806, which is widespread across the northern Holarctic region, and Stylogymnusa subantarctica Hammond, 1975 from New Zealand. Two species occur in the UK: G. brevicollis (Paykull, 1800) is widespread throughout the mainland, while G. variegata Kiesenwetter, 1845 has a more western and northern distribution and is absent from much of the south. Both occur wetland situations and may be common in marshes and sphagnum bogs. The species are medium sized, 4-6 mm, fusiform and drab dark grey or black, usually with apical abdominal tergites partly, and tarsi wholly pale. They may be distinguished by the form of the head, here the eyes are situated towards the vertex and there are 6 setiferous punctures on the dorsal surface, the apical part is produced and narrowed from the eyes and the labrum is transverse, rounded and wider than the frons, the maxillary palpi are slender and very long and the tarsi are 5-segmented. The abdomen is also characteristic, with two long style-like appendages on the penultimate segment. (5-5-5)
DEINOPSINI Heer, 1839
Includes only a single UK species, Deinopsis erosa (Stephens, 1832). This is also the only species In Europe but the genus includes a further 14 species in the Holarctic region (11 in North America) and a single species is known from Australia. The tribe also includes two (or possibly three) other genera, one of which is widespread and one of which is restricted to South America. The tribe is represented in all the biogeographical regions except for Africa. All are small, 2.1-4.2 mm, fusiform, drab coloured and densely punctured and pubescent which gives them a silky appearance which may act in a hydrophobic manner as all are associated with wetland margins, damp woodland and sphagnum bogs etc. Among our staphylinid fauna they are unusual in having 3-segmented tarsi and slender palps which are about as long as the first six antennomeres. This is among the easier of our species to identify. (3-3-3)
ALEOCHARINI Fleming, 1821
This cosmopolitan group includes almost 500 species of about 20 genera and is divided into 3 subtribes. Hodoxenina Kistner, 1970 is restricted to Cape Province and occurs in nests of the termite Microhodotermes viator (Latreille, 1804). Compactopediina Kistner, 1970 includes 10 species of 4 genera, all are obligate inhabitants of various termite nests and all have rather restricted distributions in Southeast Asia. Aleocharina Fleming, 1821 at present includes more than 450 species in about 10 genera although the generic limits are uncertain, mostly due to relationships within the large and cosmopolitan genus Aleochara Gravenhorst, 1802. The subtribe remains something of a dumping ground and at present includes all members of the tribe that do not share the highly derived features of the other 2 subtribes. Aleochara includes about 400 species and up to 16 subgenera but other genera may eventually be included while some of the subgenera may end up as distinct genera; among our UK fauna this has been suggested for subgenera Rheochara Mulsant & Rey, 1875, Emplenota Casey, 1884 and Polystomota Casey, 1908. Our UK fauna includes 33 species of 4 genera. Amarochara Thomson, C.G., 1858, which was formerly included in Oxypodini but moved to the present tribe on molecular evidence, includes about 50 species. It is Holarctic in distribution with a few species occurring in central and South America, 3 species have been recorded from the UK but all are very local and rare. Tinotus Sharp, 1883 (which may be found excluded from the present tribe in some works) includes about 40 species and is known from all the major biogeographical regions, only the single species, T. morion, is known from the UK. Aleocharina are characterized by the 5-segmented tarsi (although Tinotus is the exception here with 4-5-5 tarsal formula) and the diminutive terminal segment (pesudosegment) of the maxillary and labial palpi, this last feature is often difficult to appreciate but they appear to be 4- and 3-segmented respectively. The front and middle tibiae bear external spines, and an important character for classification purposes is the presence or absence and the general development of a mesosternal carina. In lateral view the metepimera exceed the elytral length and are obvious beyond the posterior elytral angles. Size varies from 1.5-13.0 mm, and many species are very variable in this respect, most species are broad and robust, flattened or cylindrical in form and continuous in outline, they are drab-coloured although some have striking red markings to the elytra. Larvae of Aleochara and Tinotus are parasitoids of diptera pupa whereas adults of all species, so far as is known, are predatory. Adults may be found among decaying organic matter in most habitats and some are restricted to certain habitats e.g. dung or littoral environments. Carrion is often productive and here our two large and colourful species, A. curtula (Goeze, 1777) and A. lata Gravenhorst 1802 can hardly be missed. Carrion- and dung-baited traps are usually effective in obtaining a variety of species, and flight-interception traps can also yield good results. A very good key to our UK species was provided by R. Colin Welch in The Coleopterist (Volume 6 Part 1, April 1997), this also includes a great deal of information regarding synonymy, distribution and ecology, and will provide an excellent introduction to the group.
OXYPODINI Thomson, C.G., 1859
This large and diverse tribe was formerly included, along with various other tribes, within a much more broadly-defined Aleocharini. The various tribes derived from this older classification, along with the otherwise very distinct Gymnusini, include all the aleocharine genera (at least in the UK fauna) with 5-5-5 tarsal formula. The present tribe is distinguished from the Aleocharini by the form of the maxillary palps, the form and proportions of the various segments may vary but they are clearly 4-segmented, in Aleocharini the terminal segment is diminutive and so they often appear to be 3-segmented, this tiny terminal segment is sometimes obvious but will usually need to be looked for very carefully at high magnification. A modern classification splits the group into 5 subtribes, all of which are more or less distinct. The tribe is cosmopolitan and massive, with about 2000 species in more than 150 genera in many subtribes, 5 of which are represented in the UK by 19 genera as follows. Phloeoporina Thomson, C.G., 1859 includes 5 species of Phloeopora Erichson, 1837. Oxypodina Thomson, C.G., 1859 includes 55 species in 12 genera and is dominated by the large genus Oxypoda Mannerheim, 1830 which includes 28 species in 9 subgenera. Microglottina Fenyes, 1918 includes 6 species in 2 genera. Dinardina Mulsant & Rey, 1837 includes 7 species in 3 genera, and Meoticina Seevers, 1978 includes 6 species of Meotica Mulsant & Rey, 1873. Neatly laid out the group looks straightforward; the 5-segmented tarsi and the form of the palps are easily understood but not always easy to appreciate in preserved specimens, fortunately most can be separated from similar groups on morphology and most have distinct genitalia which can be matched from figures; most of which are included in Strand & Vic (1964), see Athetini, below. The majority of species are very typical small, elongate and rather fusiform staphs but there are some unusual forms e.g. Dinarda Leach in Samouelle, 1819. (5-5-5)
TACHYUSINI Thomson, C.G., 1859
Formerly included as a subtribe of the Oxypodini but now generally considered to be a distinct tribe. All species have a 4-5-5 tarsal formula whereas in Oxypodini they are 5-segmented. The general form is very diverse, from robust and parallel-sided to slender and discontinuous in outline, but most UK species are dark and rather shiny, elongate and discontinuous with the elytra wider than the forebody and long, narrow appendages. This general habitus has often placed the species within the Falagrini but they are otherwise a very distinct group. General features of the group are: ligula divided into two diverging apical lobes, maxillae with galea and lacinia moderately elongate, neck absent or, if present, at least one-third as wide as the head, pronotum without depressions, abdomen narrower then the elytra or narrowed towards the base, mesocoxal cavities contiguous or narrowly separated, meso- and metasternal processes slender and of equal length or with the mesosternal process longer. In males the eighth tergite is usually unmodified but the ninth is usually deeply subdivided. Most species are terrestrial; many occur on the margins of ponds, lakes and streams etc and most are diurnally active. Some species occasionally occur in numbers on open areas of damp soil in warm weather. Many are very local and rare but widespread and locally common species include Tachyusa constrica Erichson, 1837, Ischnopoda leucopsis (Marsham, 1802), Thinonoma atra (Gravenhorst, 1806), Gnypeta carbonaria (Mannerheim, 1830), G. rubrior Tottenham, 1939 and Dilacra vilis (Erichson, 1837). (4-5-5)
HYPOCYPHTINI Laporte, 1835
This tribe includes about a dozen genera, it is cosmopolitan in distribution but only 3 genera occur in northern temperate regions. Cypha Leach in Samouelle, 1819 is a large and almost cosmopolitan genus, 3 species occur in North America, and of the 50 or so Palaearctic species about 15 are known from Europe and 9 of these extend north into the UK. Holobus Solier, 1849 is a large genus of more than 60 species, it occurs in the Holarctic, African and Neotropical regions. Of the 4 European species only H. flavicornis (Lacordaire, 1835) extends north into the UK. Oligota Mannerheim, 1830 is a large and cosmopolitan genus of about 150 species although it tends to be poorly represented in northern temperate regions; 10 species are known from North America and about 35 from Europe, including the Atlantic islands, of which 9 extend into the UK. Members of the tribe are small, mostly , <1.5 mm, drab-coloured and pubescent; species of Cypha are short and broad while others are elongate, All have 4-segmented tarsi and 10-segmented antennae which broaden apically to form an indistinct 3-5 segmented club. The antennae are inserted in front of the eyes but reflexed under the anterior margin of the head so that the insertions are not visible from above. All species occur among decaying vegetation, fungi and carrion etc., some are synanthropic and a few are restricted to coastal environments. Most of our UK species are very local and scarce although Cypha longicornis (Paykull, 1800) is generally common and sometimes swarms in large numbers. (4-4-4)
MYLLAENINI Ganglbauer, 1895
A large and cosmopolitan group, in Europe known from only a few species associated with fungi but otherwise much more diverse. Myllaena Erichson, 1837 includes more than 270 species and occurs throughout the world, another 10 genera are known but these are all much smaller (4 are monospecific) and limited in distribution e.g. Brachypronomaea Sawada, 1956 includes 4 intertidal species from Ryuku Islands, and Rothium Moore & Legner, 1977 includes four intertidal species from Mexico. Our UK fauna includes 11 species of Myllaena, all occur in well-vegetated wetland habitats, swamps and sphagnum bogs etc., most occur among moss during the summer and all are diurnal. Several species are widespread and locally common and should soon appear when working suitable habitats. They are drab coloured, small, <3mm, and fusiform with the elytra shorter than or as long as the transverse pronotum and strongly tapering abdomen, the legs are slender and the tarsi are 4-4-5. The dorsal surface is densely and very finely punctured and pubescent, giving specimens a silky appearance. The maxillary palpi are long and slender; about as long as the basal 4 or 5 antennomeres. (4-4-5)
DIGLOTTINI Jakobson, 1909
This small tribe includes 5 species of the Holarctic genus Diglotta Champion, 1887 and a single species of Paradiglotta Ashe & Ahn, 2004 which has recently been discovered in New Zealand. Two species of Diglotta occur very locally in Europe and both occur in the intertidal zone on sandy beaches. They are very characteristic in appearance; 1.4-2.5 mm long, elongate, narrow and discontinuous in outline, head slightly wider than the pronotum which tapers to the base and with long legs and strongly-protruding mouthparts. The tarsi are 4-segmented and the maxillary palpi are slender and very long. In Europe they display dimorphism with both species occurring in smaller flightless forms with shorter elytra, and larger, fully-winged forms with longer elytra. Both forms are widespread though very local and scarce around the coasts of England and Wales. (4-4-4)
AUTALIINI Leach in Samouelle, 1819
Includes about 10 genera, most are small; the largest are Eudera Fauvel, 1866, Gansia Sharp, 1882 and Ophioglossa Fauvel, 1886, each with about 15 Neotropical species, and restricted to various tropical regions. Only Autalia Leach, 1819 is known from northern temperate regions, it reaches south into Central America and the Oriental region but is absent from the tropics. The species are easily recognized by the deep longitudinal impressions at the base of each elytron. (4-4-5)
HOMALOTINI Heer, 1839
This cosmopolitan and very large tribe (although the limits are not certain) includes more than 120 genera. The classification remains uncertain, 4 subtribes are commonly recognized but others will be found in the literature e.g. Rhopalocerina Reitter, 1909 and Leptusina Feynes, 1918 are now usually included within the Bolitocharina Thomson, C.G., 1859. The tribe is morphologically very diverse and includes slender and fusiform as well as parallel-sided, short and very broad species. It is difficult to define as most of the prominent features are to be found in other tribes, but the 4-4-5 tarsi coupled with various features of the mouthparts such as molar regions on the ventral surface of the mandibles (etc.) are usually sufficient to define the group. The subtribes are also defined by subtle features of the feeding apparatus and sometimes by more easily appreciated features such as the widely separated mesocoxae in Gyrophaenina Mannerheim, 1830. In a practical sense most of this is more or less useless but our UK species are readily keyed-out on general morphology. The UK fauna includes 45 species of 17 genera and 4 subtribes. Silusina Feynes, 1918 includes only Silusa rubiginosa Erichson, 1837, a widespread though very local and scarce species associated with decaying trees. Homalotina Heer, 1839 includes 3 species of 3 genera, 2 of these, Homalota plana (Gyllenhal, 1810) and Anomognathus cuspidatus (Erichson, 1839) and widespread and generally common while Cyphea curtula (Erichson, 1837) is a recent addition to our fauna and known from only a few records. All occur under bark. Bolitocharina includes 18 species of 9 genera, most are very local but some Bolitochara Mannerheim, 1830 and Leptusa Kraatz, 1856 are widespread and locally common. Most are associated with decaying wood and fungi although our 2 species of Euryusa Erichson, 1837 are usually associated with ant nests in tree hollows. Gyrophaenina Kraatz, 1856 includes 23 species of 4 genera; all are associated with fungi and may be abundant among the gills of soft fleshy sporocarps during the summer. The widespread and locally common Agaricochara altissima (Stephens, 1832) is associated with Daedalea quercina (L.) Pers. (1801) on oak, Encephalus complicans Stephens, 1832 is also widespread and locally common but Brachida exigua (Heer, 1839) is very rare and known from only o few records from southeast England. Many of our species of Gyrophaena are widespread, they often appear in large numbers during the summer and a single fruiting body may host several species. All our species may be identified from Mike’s insect keys.
HYGRONOMINI Thomson, C.G., 1859
Includes 9 genera but only Hygronoma Erichson, 1837 is known from the Western Palaearctic area. Our single species of Hygronoma is sufficiently distinct to be instantly recognizable, even with a hand lens in the field. The species is small, 2.5-3.0 mm, flat and elongate, the body is dark grey with striking bicoloured elytra and the appendages are pale red. The antennae are 11-segmented and filiform while the tarsi are 4-segmented and slightly dilated-an adaptation to climbing vegetation. It is generally common across England and Wales in wetland situations, including salt marshes, and may be abundant in reed beds during the summer. (4-4-4)
PLACUSINI Mulsant & Rey, 1871
This is a small tribe of five genera; Euvira Sharp, 1883 is widespread in the New World, Kirtusa Pace, 2008 is known only from Ecuador, Speiraphallusa Pace, 2013 is described from Mayaysiam and the Placukorna Santiago-Jiménez, 2016 is known from a volcano in Veracruz. Placusa Erichson, 1837 has a worldwide distribution; 9 species are recorded from North America, 44 from South America, 5 from the Australasian region 51 from the Oriental region and 44 from the Palaearctic region of which 10 occur in Europe and 4 extend to the UK. All European species occur under bark and of the UK species only P. pumilo (Gravenhorst, 1802) and P. tachyporoides (Waltl, 1838) are widespread although the latter is very local and uncommon. They are elongate and rather broad species, resembling many Athetini in general appearance. The head is much narrower than the pronotum and usually has a shiny transverse seam between the antennal insertions. Antennomeres 6-10 strongly transverse. The pronotum is transverse, broadest about the middle and produced back across the base from rounded or obtuse posterior angles; the surface is clearly punctured throughout, lacks distinct impressions and has backwardly-oriented pubescence. The elytra are transverse and only slightly wider than the pronotum with the base straight or curved but not sinuate before the posterior angles. Basal segment of the hind tarsi longer than the next two combined. The eighth tergite is longer than those preceding and, in males, has characteristic projections to the apical margin which are invaluable for specific identification. (4-4-5)
ACTOCHARINI Bernhauer & Schubert, 1911
Formerly included in Phytosini but now assigned to the present tribe (along with a single Mediterranean member of the genus), Actocharis readingii Sharp, 1870 is a very local species presently known from coastal areas of the West Country and South Wales. The species occurs among shingle or under large stones in the intertidal zone or about the high tide mark, it is tiny, 1.5-2.0 mm, and flightless and so may well be more common and widespread than records suggest. The species is very distinctive; elongate, narrow and discontinuous in outline, entirely yellow with at least some basal abdominal tergites darkened. The head is about the same size as the pronotum and the elytra are shorter, the eyes are very small and the antennae are longer than the head and pronotum combined. (4-4-5)
PHYTOSINI Thomson, C.G., 1867
Formerly included in a much more widely defined Bolitocharini, this tribe includes 3 genera; Phytosus Curtis, 1838 (8 spp.), Arena Fauvel, 1862 (2spp.) and Cameronium Koch, 1936 (9spp.) the first 2 are mostly European while the last is mostly African in distribution. So far as is known all species occur among organic detritus in sand or among rocks about the high tide mark or in the intertidal zone. The UK fauna includes 2 species of Phytosus and Arena tabida (Kiesenwetter, 1850); they are all widespread though very local and rare. All species are small, 2.5-3.0 mm, elongate and rather parallel-sided although the abdomen is usually widened towards the apex. The dorsal surface is densely pubescent, pale brown with the forebody and often various abdominal tergites, darker, and the appendages are pale yellowish. The antennae are 11-segmented with the distal segments strongly transverse. The tribe is characterized by the 4-4-5 tarsal arrangement and the presence of stiff setae along the outer margins of the front and middle tibiae. (4-4-5)
ATHETINI Casey, 1910
This large and very difficult group occurs in most habitats throughout the world and, probably fair to say, is of indeterminate diversity. New species are being described, especially from less studied parts of the world such as China and South America, and the list is increasing rapidly, but molecular studies are revealing much hidden diversity and thus several groups have recently been split to form distinct tribes e.g. Geostibini and Lomechusini, although it must also be acknowledged that some tribes have been described without such justification. The present diversity includes more than 170 genera and many thousands of species; the genus Atheta Thomson, C.G., 1858 alone includes about 1700 species. Despite the long list of subtribes to be found in various works, the majority are of doubtful value and until a thorough molecular analysis is available many of these systems are likely to be revised. Identification, even for restricted faunas such as our own, is very difficult and will usually depend on dissections, and despite the tribe being relatively well-defined it can be difficult to assign specimens due to difficulties in counting tarsal segments. In general terms the tribe is defined as follows: Antennae 11-segmented, tarsi 4-5-5, mesoventral process narrow and meso-coxae narrowly or only moderately separated, galea and lacinia moderate in length, labial palpi 3-segmented, maxillary palpi 4-segmented, the first segment membranous internally and with spines at least in the apical half, and ‘athetine bridge’ of the aedeagus present (this is a narrow transverse sclerotized strip visible anterior to the broad basal compressor plate of the median lobe and visible in ventral aspect), these characters are present in combination and none is unique to the group. In practice, and because the same applies to several other groups, members of other tribes will often be put through keys to this tribe because the tarsal segments are difficult to count, especially those on the front legs (this cannot be stressed enough), but they are sometimes relatively easy to distinguish from other superficially-similar groups with the same tarsal formula e.g. from Lomechusini by the habitus or the lack of broadly-rounded cheeks, or from Falagriini by the absence of a constricted basal margin to the head. Regarding identification, some really good keys and lots of information can be found at Mike’s insect keys or at the various pages by Arved Lompe. Our UK fauna includes 2 species of Thamiaraea Thomson, C.G., 1858, in the subtribe THAMIARAEINA Fenyes, 1921, and 187 species of 26 genera in the subtribe ATHETINA Casey, 1910; this includes 125 species of Atheta Thomson, C.G., 1858 included in 22 subgenera, many of which are referred to as distinct genera in older works. Features useful for identification include e.g. the relative proportions of body parts, including appendages and especially regarding antennal segments, the form of the pubescence on various body segments but especially on the pronotum (this can be used to assign many species of Atheta to various groups), the presence or absence of setae to body parts and appendages, the form the abdominal segments (especially regarding transverse basal impressions), and sometimes the colour of various body parts and appendages. Very often (usually) the crucial clue to identification lies in the form of the genitalia, and this applies to both sexes, Very good figures of most species can be found online, and a very broad overview of these (which is still useful but out of date and sometimes difficult to use because of nomenclatural changes) was given by Strand & Vik (1964) which is available HERE. Identification requires a good stereo microscope of up to X100, good and variable lighting and good dissection skills. High magnification can often discern obscure tarsal structures, and immersing the tarsi in a drop of water and varying the lighting can be effective. Dissection is a subject we intend to delve further into elsewhere but the following should help. Very fine forceps and needles are essential; forceps such as the D4040 model from Watkins and Doncaster are very adequate, but regarding pins it is essential to find a size that is personally useful as very fine pins can be too ‘springy’ for many people and tend to do more harm than good. Fresh specimens are usually easy to work with but older carded material can be difficult and will need to be softened before it is touched. With practice and care the apical part of the abdomen can be softened and removed from a mounted specimen without damage; dilute Potassium hydroxide (KOH) can be applied with a fine brush to the end of the abdomen (although capillary action tends to take it along the entire length and the whole thing will then need to be removed, but this is not important). Once removed the apical tergites and sternites can be added to a drop of KOH to further soften them and they can be separated by inserting a fine pin and gently working it along the lateral margins. For this work I find an excavated slide to be ideal as most excavated glass blocks tend to be too large and obtrusive for very fine work. The plates can then be unfolded and the insides inspected; when present the aedeagus is obvious, even when enclosed in fatty tissue, but when absent the spermatheca must be looked for very carefully as females tend to contain more fatty tissue than males. KOH is a very good fat solvent and so adding a drop with a fine brush and then removing it with a finely-twisted tissue will remove lots of obscuring fatty tissue and leave the spermatheca in place (sometimes it sticks to the tissue but can be easily spotted). The various parts can be cleaned up by adding and removing drops of distilled water followed by weak acid to neutralize the basic KOH (any organic acid will do as they tend not to dissociate very much; I use white vinegar and it works fine). Once clean the plates can be splayed and glued to the specimen card, the genitalia are best examined at this stage as they can be manipulated to negate artefacts that appear once they are glued down. Some workers preserve the genitalia on permanent slide mounts with glycerine or other suitable mountants but these will need to be stored remote from the specimen and there is always the chance that they will become lost. Much better to stick genitalia to the specimen card using Dimethyl Hydantoin Formaldehyde (DMFH), which is very robust and dries clear so that the bits can be examined without removing them, and if they need to be removed it is (eventually) water soluble and so can be softened without harming them. Finally it cannot be stressed enough that any specimens reliably named by dissection followed by a careful consideration of the morphology will be a very valuable addition to the reference collection. Needless to say that species of this tribe occur in every type of habitat and many may be found at any time of year, there are many to be found in mammal, bird and insect nests and, especially at the wider world scale, the group includes many very specialized tribes, genera and species e.g. the 10 genera of the Neotropical tribe Ecitocharini Severs, 1965 (which remain of uncertain placement but may well belong with the Athetini) are associated with army ants (Eciton Latrielle, 1804). (4-5-5)
TAXICERINI Lohse, 1989
This small group was formerly included within the much more extensive Athetini and it is still sometimes regarded as a subtribe of that group. They do not differ especially on external morphology and key readily to Athetini, but they differ in the structure of the mouthparts, especially the mandibles which are long, straight and curved at the very apex; in Athetini they are regularly curved from the base. Three genera are included: Taxicera Mulsant & Rey, 1873 includes about 25 species and is mostly Mediterranean in distribution, the monotypic Discerota Mulsant & Rey, 1874 is endemic to France, and Halobrecta Thomson, C.G., 1858, with about 8 species is Holarctic. Our UK fauna includes only 4 species of Halobrecta. Halobrecta are halophilic and almost exclusively restricted to coastal areas where they occur on sandy beaches under decaying seaweed. Two of our species, H. algae (Hardy, 1851) and H. flavipes Thomson, C.G., 1861 are widespread and, although very local, sometimes appear in numbers and may be found, sometimes together, by sieving suitable material. Halobrecta are small, 2.4-3.2 mm, flattened and elongate species, drab grey or brown with dark antennae and paler legs. These are very ‘ordinary’ looking members of the subfamily, with few distinguishing features but the dorsal surface is very finely pubescent, and the arrangement of this on the pronotum and elytra, coupled with the general habitus, are a good guide to the genus. The legs are long and slender and the tarsi, which are 4-5-5, may defy all attempts to count the segments. (4-5-5)
GEOSTIBINI Seevers, 1978
Formerly included within Athetini, this tribe is distinguished by extremely subtle features of the feeding apparatus (reduced sensillum a of the epipharynx) and forms a sister group to the Lomechusini. The extent of the tribe is not known, a relatively small number have been confirmed but this is likely to grow significantly as research continues. The UK fauna includes 20 species of 4 genera, As a group they are not distinct on morphological features from the Athetini in general and so will need to be keyed along with that group, they are all rather nondescript rove beetles and very typical of the family. (4-5-5)
LOMECHUSINI Fleming, 1821
Formerly included within a more broadly-defined Athetini, and now regarded as distinct and a sister group to the Geostibini, seehttps://www.docin.com/p-1729983636.html Although rather poorly represented in the UK, this tribe is otherwise very diverse and well represented in most regions, especially across the Palaearctic region, and despite numerous changes of nomenclature and a general shuffling between tribes, the group currently includes about 2500 species in more than 200 genera and at least 4 subtribes. Regarding our UK fauna, the subtribe LOMECHUSINA Fleming, 1821 includes 3 species of two genera which are sufficiently distinct to be reliably identified on general morphology (although species of Dinarda (Oxypodini) are similarly bizarre in appearance but abundantly different in detail.) Of interest here are the thick tufts of yellow hairs (trichomes) on the lateral margins of the basal abdominal tergites. Subtribe MYRMEDONIINA Thomson, C.G, 1867 includes 10 species of 4 genera which are much more typical of the subfamily in general appearance. The group is distinguished on rather obscure features of the mouthparts e.g. the membranous apical section of the maxillae extends beyond the other mouthparts, but features such as the broadly curved cheeks and elongate metanotum which extends beyond the elytral apices and appears as a large rounded lobe in lateral view. The species are small to medium sized, 3.5-6.5 mm, and while rather nondescript they are sufficiently distinct to key reliably in Joy’s handbook; Drusilla is unmistakable (and our only member of an almost worldwide genus of more than 160 species) while our species of Zyras Stephens, 1835 (which according to a recent analysis is almost cosmopolitan and includes more than 800 species in 54 genera) are bicoloured and will soon become familiar, species of Pella Stephens, 1835 and Myrmoecia plicata (Erichson, 1873) will need to be keyed very carefully but should straightforward. Most of our species are associated with ants and, beyond dispersing during the summer, are rarely found outside their nests. Species of Lomechusa Gravenhorst, 1806 are more specialized and many are thought to be host-specific or associated with narrow range of hosts. (4-5-5)
FALAGRIINI Mulsant & Rey, 1873
This is a cosmopolitan tribe of about 30 genera, 7 of which are represented in the UK by 11 species. The tarsal formula is 4-5-5 and the species are characterized by their small size, <3.5 mm and the form of the head which is strongly converging across the base to a narrow neck, some members of other tribes also have this head structure but are otherwise distinct on tarsal formula or external morphology. Our 4 species of Myrmecopora Saulcy, 1865 occur under stones near the high tide level and all are very local and rare. Cordalia obscura (Gravenhorst, 1802) is locally common across England and Wales though rare in the north and is known from Southern Scotland and Northern Ireland, it occurs among decaying organic matter such as compost, carrion and dung and occasionally in avian nests. Borboropora kraatzii Fuss in Kraatz & Fuss, 1862 is a very rare species with only a few modern records from Kent, adults have been found by sweeping grassland. Cordalia obscura (Gravenhorst, 1802) is locally common across Wales and southern England and extends sporadically north into Scotland and Northern Ireland, it occurs among compost, dung and leaf litter and has been recorded from old avian nests. Our 2 species of Falagria Leach in Samouelle, 1819 are widespread though very local and generally scarce, both occur in compost etc. The widespread though very local Falagrioma thoracica (Stephens, 1832) inhabits wetlands and permanently damp woodland. Myrmecocephalus concinnus (Erichson, 1839) is an established introduction from South America or East Asia, first recorded in Europe during the early 20th century it has spread rapidly since then. There are widely-spaced records from south east England, East Anglia and Wales and it is likely to become more widespread. Adults occur among fermenting compost and straw in gardens and farms. The Eastern Palaearctic Bohemiellina flavipennis (Cameron, 1920) is an invasive species which regularly occurs among horticultural products in Europe but there seem to be no modern records from the UK. This can be a very difficult species to place because the tarsi appear to be 4-segmented; the basal segment being short and almost completely obscured by the ends of the tibiae. Because of the 4-5-5 tarsal formula, Joy keyed these genera out among a much larger group (his Myrmedoniini) which includes Athetini and several others, and as such they are lost in the wider detail and become difficult to identify, but Mike Hackston provides a very good key to the tribe according to modern classification. (4-5-5)