OMALIINAE MacLeay, 1825

The presence of 'false eyes' makes these distinctive among our rove beetles. Includes some very common and widespread species, and occur in a very diverse range of habitats.

Suborder:

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POLYPHAGA Emery, 1886

STAPHYLINOIDEA Latreille, 1802

STAPHYLINIDAE Latreille, 1802

5

28

Approx. 70

1.5-7mm

Introduction

Members of this group are readily recognized by the presence to two ‘ocelli’ on the vertex of the head about the level of the hind margin of the eyes, these may be difficult to detect (and in some exotic species they are missing) where the surface is strongly punctured, microsculptured or otherwise uneven, but with good light and decent magnification they usually appear as small round areas contrasting in colour to the surrounding cuticle; they are not eyes in the same sense as the simple eyes seen in many hymenoptera but simply a part of the internal supporting structure of the head. The only other UK species with such a structure is Metopsia clypeata (Müller, P.W.J., 1821) (Proteininae Erichson, 1839) but here it is single and placed at the centre of the vertex. They are otherwise a very variable but somehow distinctive group and one that will become largely familiar with experience of a few genera. Typically they are elongate, rather broad, flattened and discontinuous in outline, in many the elytra are longer than in most staphylinids and the abdomen correspondingly more covered, in the field many look superficially like small carabids. Most are drab coloured, brown to black although commonly the elytra are contrastingly paler, either entirely or in part. The dorsal punctation and pubescence is very variable but in most the entire surface is randomly and rather finely punctured and finely pubescent. The head is proportionally small and often strongly sculptured, the eyes convex and prominent, temples short and strongly tapering and the antennae long, 11-segmented and filiform to gradually broadened towards the apex, inserted anteriorly or laterally outside the outer margin of the mandibles and often hidden beneath an expanded clypeal margin. The pronotum is very variable from widely transverse to elongate and from smoothly convex to heavily sculptured wit longitudinal furrows, fovea or ridges.  Elytra elongate, with distinct and rounded shoulders rounded posterior angles, usually randomly punctured but in some with regular and strongly-punctured striae. Wings very variable; in most species well-developed but in some brachypterous or apterous. Abdomen broad at the base and then parallel-sided, expanded or strongly tapering to the apex; the first one or two visible tergites have a pair of wing-folding structures-tomentites-which appear as round microsculptured or pubescent areas contrasting with the surrounding cuticle. Legs usually slender and rather long; coxae conical and  close  together,  the  hind  pair  often  strongly  projecting,  trochanters

long, especially the hind pair. In most the femora and tibiae are simply long and only weakly broadened, unarmed and with small spurs. Tarsi 5-segmented and very variable.  The group is morphologically very diverse and so a general description would be both protracted and pointless as a good familiarity can be gained by searching pictures online, and they can be distinguished by the ‘ocelli’ and antennal placement etc. The 1400 or so species are classified into more than 115 genera and 7 tribes, of which 5 occur in the UK; some of our species represent large and widespread genera and so will provide a good introduction to the group. The subfamily is most diverse in northern temperate regions. The two non-British tribes are small and of restricted distribution:

  • Corneolabiini Steel, 1950 is a southern hemisphere group of 3 genera, it is most diverse in forest regions of Australasia but also occurs in South America, and many new species have been recently described.

  • Aphaenostemmini Peyerimhoff, 1914 includes 2 Old-World genera; Aphaenostemmus Peyerimhoff, 1914 includes 7 species from Asia, extending west into Turkey, Greece and North Africa, Giulianium Moore, 1976 are small intertidal species which lack ocelli, they occur in the far east of Asia and North America.

The remaining tribes are represented in the UK as follows:

  • Coryphiini Jakobson, 1908 includes 24 genera of which 11 occur in the Nearctic region and 20 in the Palaearctic region.

    • Coryphium Stephens, 1834 includes 22 species, 3 are Nearctic and 19 are Palaearctic although they are most diverse in Asia; 6 occur in Europe but 5 of these have limited distributions and only the very widespread C. angusticolle Stephens, 1834 extends to the UK.

    • Eudectus Redtenbacher, 1857 includes a single Nearctic species, and 6 Palaearctic species. Of the 2 European species only the very local E. whitei Sharp, 1871 occurs in the UK, it is a very rare insect of the Scottish Highlands and known elsewhere in Europe only from the Netherlands.

  • Eusphalerini Hatch, 1957 is a monogeneric tribe.

    • Eusphalerum  Kraatz, 1858 is the largest genus within the subfamily with about 300 species occurring in the Holarctic and Oriental regions, 27 species are listed from North America while the Palaearctic region includes about 245 species, most of which occur in Asia and are restricted to certain areas, very few are widely distributed, the faunas of various countries e.g. Japan, are very diverse and a considerable number inhabit mountainous regions. The European fauna is much more diverse in warmer southern regions e.g. 57 species are listed from Italy while less than 30 occur in central regions and 20 are listed from Poland. The UK fauna includes 6 species, all of which are widespread in Europe and extend variously into Asia. Unlike most members of the family the adults visit flowers, often in abundance and often in wooded situations, where they feed on pollen and nectar. Many species are abundant in broadleaf and coniferous forests in northern temperate regions, some extending north above the Arctic Circle, and when large numbers occur on flowers there is often a mixture of species. Most species visit a range of flowers and members of the genus have been recorded from those of about 25 plant families. Many species occur in wet upland situations and in North America they have been recorded above 4000m. Little is known of the biology but larvae are thought to develop in soil near to where the adults are found. Species are small, 1.5-4.0mm, and rather nondescript; broadly elongate and pale- to dark-brown or black, only rarely with distinctive colour patterns but they are distinct from other genera of the subfamily and easily distinguished by the rather broad tarsi which are fringed with long setae. The following general description applies to most of the species. Finely and randomly punctured, often more coarsely so on the elytra, microsculpture variable but usually quite strong, at least on the forebody. Head transverse with convex and prominent eyes and short, tapering temples, often produced anteriorly and with various impressions anterior to the ocelli on the vertex and clypeus. Antennae 11-segmented and gradually thickened towards the apex, typically with segments 8-10 transverse, palps short with the apical segment narrower than the penultimate and tapering to a point. Pronotum transverse and weakly convex, evenly rounded laterally or distinctly sinuate towards the base, lateral margins distinctly bordered and usually only narrowly explanate, this applies to the UK fauna but is otherwise very variable e.g. in the European E. rectangulum (Fauvel, 1869) the pronotum is flat and widely explanate. Elytra long and dilated apically, often separated towards the apex or produced at the apical angle. Abdomen mostly covered by the elytra, usually with four or five transverse and strongly-bordered tergites exposed. Legs short and slender; femora narrowly visible from above, tibiae straight or slightly-curved, weakly broadened to the apex and with very fine apical spurs. Tarsi 5-segmented; basal segments broad and densely setose, terminal segment long and curved, as long as or longer than the others combined.​

  • Hadrognathini Portevin, 1929 is a small Palaearctic group of 2 genera; the monotypic Brachygnathellus Zerche, 1991 from south-eastern Europe, and Hadrognathus Schaum, 1852 which includes a species from Portugal and Spain, and the western European H. longipalpis (Mulsant & Rey, 1851), the type species, which has recently been added to the UK list.

  • Omaliini Macleay, 1825 includes 43 genera, species occur worldwide and it is the only tribe within the subfamily to occur in tropical regions; about 50 species of 15 genera occur in the Nearctic region while more than 220 species of 23 genera are Palaearctic. The UK list includes 12 genera and 38 species; all the larger northern temperate genera are represented and so our fauna provides a good representation of the tribe as a whole. Species are typically associated with decaying vegetation including fungi in a wide range of habitats including woodlands, dunes and beaches, birds’ nests and garden compost; adults often occur among extraction samples or may be found on walls and trunks etc. or by sweeping . Typical of the tribe are members of the Holarctic genus Omalium Gravenhorst, 1802, which includes 14 Nearctic species but is very diverse in the Palaearctic region with about 80 species, mostly from Asia but the European fauna is also diverse and 13 have been recorded from the UK, several are common and widespread and should soon be found by general searching. Our single species of the Palaearctic genus Acrulia Thomson, C.G., 1858, A. inflata (Gyllenhal, 1813) is associated with decaying wood and is generally rare though widespread across Wales, the midlands and the Scottish Highlands. Of the 10 Palaearctic species of Acrolocha Thomson, C.G., 1858, 2 are widespread and locally common across Wales and southern England, both occur among decaying vegetation and occasionally in dung. Phyllodrepa Thomson, C.G., 1859 is a Holarctic group with 17 species recorded from the Palaearctic region and 11 from North America, four occur in the UK but only P. floralis (Paykull, 1789) is at all common, all in the south among decaying vegetation and are occasionally found on flowers. Dropephylla Mulsant & Rey, 1880 is a large genus of 34 Palaearctic species and a further 2 from North America. Six species occur in the UK but only 2, D. vilis (Erichson, 1840) and D. ioptera (Stephens, 1834) are locally common and widespread while 3 are more-or-less confined to the Scottish Highlands. Hapalaraea Thomson, C.G., 1858 includes a single UK species, H. pygmaea (Paykull, 1800) which is widespread though local across Wales and the south of England; it is associated with fungi and decaying bark. Hypopycna rufula (Erichson, 1849) is a very rare species associated with tree hollows and leaf-litter; it has been recorded a few times from Surrey and Kent. Our 2 species of Phloeonomus Heer, 1839 are widespread in the south and associated with decaying bark; the widespread though local P. pusillus (Gravenhorst, 1806) on conifers, and the much more common P. punctipennis Thomson, C.G., 1867 on deciduous trees. Phloeostiba Thomson, C.G., 1858 includes 2 UK species; P. plana (Paykull, 1792) is widespread though very local in the south while P. lapponica (Zetterstedt, 1838) is known from only a few records from the Scottish Highlands. Both are associated with bark and decaying timber and are predatory on bark beetle larvae etc. Paraphloeostiba gayndahensis (Macleay, 1873) has only very recently been added to our list, it is native to Australia and has been widely and accidentally introduced into Europe and North America, it appears to be spreading and adults are associated with decaying plants and fruit and sometimes occur on flowers. Our three species of Xylodromus Heer, 1839 are associated with decaying vegetation; X. depressus (Gravenhorst, 1802) and X. concinnus (Marsham, 1802) are widespread across the south of England and Wales while X. testaceous (Erichson, 1840) is known from only a few widely-spaced southern records. Two species of Xylostiba Ganglbauer, 1895 occur in the UK; X. monilicornis (Gyllenhal, 1810) is a rare species of Wales and the Scottish Highlands while X. bosnica (Bernhauer, 1902) has only recently been recognized, there are a few records from the Coventry district and elsewhere in the south. In Europe it is associated with bark on broadleaf trees, mostly in upland and mountain districts.

  • Anthophagini Thomson, 1859. This tribe includes about 40 genera which are distributed throughout the Holarctic and Oriental regions; 27 genera occur in the Nearctic region and 31 in the Palaearctic. It is by far the most diverse tribe with more than 500 Palaearctic species; the greatest diversity is in the Asian region and many genera are confined, or almost confined, to Asia e.g. Hydrodromicus Tronquet, 1981 (14 spp.) or Mannerheimia Mäklin, 1880 (17spp.) and the 29 species of Philyrodes Bernhauer, 1929 are endemic to Japan. The largest genus is Lesteva Latreille, 1797, although the limits are yet to be defined, with between 75 and 115 species and a further 2 from the Nearctic region, they are wetland species occurring in moss etc. and on the continent many occur in upland or mountain regions, 12 occur in central and Northern Europe of which 6 extend to the UK and of these at least 3 of these are common and widespread. Anthobium Samouelle, 1819 is a large genus with 33 Palaearctic and 12 Nearctic species The UK fauna includes 2 widespread and locally common species, they occur in decaying fungi, leaf-litter and moss, mostly in wooded habitats. Olophrum Erichson, 1839 includes 40 Palaearctic species of which 4 occur in the UK, of these 3 are rare and very local; 2 from Scotland and one from the fens of eastern England, only O. piceum (Gyllenhal, 1810) is widespread and locally common, it occurs among vegetation in open habitats such as grassland and moorland. Only one of the 5 Palaearctic species of Deliphrum Erichson, 1839 extends to the UK; D. tectum (Paykull, 1789) is a very local insect of northern England and Wales, adults are found in decaying vegetation and dung. Our single species of Arpedium Erichson, 1839, A. brachypterum (Gravenhorst, 1802) is a rare insect occurring in moss etc. on heather moors in mountainous districts in Wales and northern parts of the UK. Two species of Acidota Stephens, 1829 are widespread; A. cruentata Mannerheim, 1830 across England and Wales, and A. crenata (Fabricius, 1792) extending north to the Scottish Highlands and Western Isles, both occur in decaying vegetation and moss. Phyllodrepoidea crenata (Ganglbauer, 1895) is a very local and rare species with widely scattered records in England and Scotland, and most records are from Wales, further afield it is confined to Europe where it extends north into southern Fennoscandia. Adults occur in moss and fungi on decaying deciduous and, rarely, coniferous trees, mostly in upland and mountain regions. Geodromicus is a large genus with about 110 Palaearctic, and mostly Asian, species, 28 occur in Europe although most of these are of very restricted distribution; 2 very widespread European species extend to the UK. Both occur in moss etc. in wooded upland and mountain regions in Wales, northern England and Scotland. Only 2 of the 40 or so Palaearctic species of Anthophagus Gravenhorst, 1802 occur in the UK and both are very widespread throughout Europe; A. alpinus (Paykull, 1790) is a very rare species with scattered records from Northern England and Wales and the Scottish Highlands while A. caraboides (Linnaeus, 1758) is a more common and widespread species with a mostly western and northern distribution. Adults occur under debris and in decaying vegetation, often in wetland habitats, and appear on flowers in the spring. Of the five Palaearctic species of Orochares Kraatz, 1857, only O. angustatus (Erichson, 1840) is widespread in Europe, extending north to the UK where it is known from only a few records from the south of England. Adults occur year-round and are associated with decaying vegetation, in Europe it occurs in garden compost heaps. Micralymma Westwood, 1838 includes 3 European species but only M. marinum Ström, 1783) is widespread, it is very local maritime species of northern and western Europe including the UK where most records are from Wales and northwest England. Philorinum Kraatz, 1857 includes 8 Palaearctic species; most have a restricted Asian distribution, but P. sordidum (Stephens, 1834) occurs throughout Europe, it is rare through much of its continental distribution but is locally common across England and Wales and there are scattered records north to the Scottish Highlands. Adults occur on various flowers during the summer but many records have been from gorse and broom.

Members of the larger tribes are morphologically diverse and so keys tend to work at the generic level e.g. that of Tottenham (1954) which can be ambiguous and very frustrating to use but there is a well-illustrated and almost complete key to our UK species HERE.

UK Genera
Omaliini MacLeay, 1825

Acrulia

1 species

Omalium

13 species

Phyllodrepa

4 species

Phloeonomus

2 species

Dropephylla

6 species

Hapalaraea

1 species

Hypopycna

1 species

Acrolocha

2 species

Phloeostiba

2 species

Paraphloeostiba

2 species

Xylostiba

2 species

Xylodromus

2 species

Eusphalerini Hatch, 1957

Eusphalerum

6 species

Hadrognathini Portevin, 1929

Hadrognathus

1 species

Anthophagini Thomson, C.G., 1859

Anthobium

2 species

Olophrum

4 species

Deliphrum

1 species

Arpedium

1 species

Acidota

2 species

Phyllodrepoidea

1 species

Lesteva

6 species

Geodromicus

2 species

Anthophagus

2 species

Orochares

1 species

Micralymma

1 species

Philorinum sordidum.jpg
Coryphiini Jakobson, 1908

Eudectus

1 species

Coryphium

1 species

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