Liothorax Motschulsky, 1860
This Holarctic genus was formerly included as a subgenus of Aphodius Illiger, 1798, it includes ten species of which five occur in North America and five are Palaearctic. They are mostly associated with seasonal temperate regions although two of the Nearctic species extend south into Mexico. All the Palaearctic species are widespread, they all occur in Europe and two of these, including the type species L. plagiatus (Linnaeus, 1767) extend to the UK (see below). They are slightly unusual among the subfamily as they are not generally associated with dung, they are mostly found in marshes and marginal wetland situations, often near the coast, and especially where there is plenty of decaying organic matter or where it is disturbed and polluted by cattle etc. All species are seasonal, occurring and breeding in spring and early summer, with larvae developing in early summer and new generation adults appearing in late summer and autumn and overwintering. Both adults and larvae are saprophagous detritivores.
All species are small, ranging from 3.0 to 6.0 mm. they are glabrous and most are entirely black or faintly metallic although some have narrow pale margins or flecks of red to the elytra. A few species are very variable with respect to elytral colour e.g. in the Nearctic L. alternans (Horn, 1870) these range from entirely black to black with complete longitudinal yellow stripes. The head is not tuberculate but there is a transverse clypeal ridge which is often more prominent in males, the pronotum lacks a basal border, the scutellum is constricted and parallel-sided towards the base and the hind tibiae are fimbriate with apical spinules of equal length. Other characters which are useful for identifying the genus among our UK fauna are the form of the clypeus; bisinuate apically and obtusely angled and rounded in front of the eyes, substantially black anterior pronotal angles, wide and flat elytral intervals and the narrow-no wider than an adjacent stria-elytral margin around the apex. Our two species are readily separated by the form of the tarsi:
Liothorax plagiatus 1
Liothorax niger 1
Liothorax plagiatus 2
Basal hind tarsomere shorter, or at most as long as, the longer corresponding tibial spur. Basal mid-tarsomere shorter than the longer corresponding tibial spur. Clypeus finely punctured and often rugose. Elytra often with a reddish fleck on the disc.
Basal hind tarsomere longer; at least as long as, and often longer than the longer corresponding tibial spur. Basal mid-tarsomere at least as long as the longer corresponding tibial spur. Clypeus smooth and finely punctured. Elytra black.
Liothorax niger (Illiger, 1798)
This very widespread Palaearctic species occurs throughout Europe except for the north of Fennoscandia and southern areas of the Iberian and Balkan Peninsulas, it is present on most of the Mediterranean islands but not in North Africa, and it extends east through Asia Minor and Russia to the far east of Asia and China. In northern Europe, where it is very local and generally rare, there may have been a general decline over the twentieth century as in some countries e.g. Poland, its presence in many areas is based on older records. In the UK it is locally common across south Hampshire, especially in the New Forest which seems to be the historical stronghold of the species although there are older records from Dorset, it has also recently been found in Berkshire and it seems likely that further, more widespread, records from the south are likely. The species is generally associated with wetland margins and permanently damp soils; across much of Europe and Asia the species is most prolific in open areas between 1000 and 2000m but it is often abundant in lowland areas where it has been found causing damage to golf turf. In the UK it has been recorded from cattle dung but the usual habitats are heathland pond and river margins, especially where these are trampled by cattle and the soil enriched by dung and urine. Adults occur year-round, they overwinter in the soil and are active in late spring and summer, peaking in abundance during June and July and then occurring in small numbers until the autumn when they sometimes appear in numbers. The usual habitat is among dead leaves and detritus on disturbed soil close to water, and adults may be abundant in the spring among debris deposited from woodland or vegetation by winter floods, beyond this they may be found on grazed heathland alongside other small Aphodiinae. Adults are saprophagous, they disperse by flight in spring and early summer and sometimes swarm in large numbers and so might occur away from typical habitats. Searching among accumulated debris near disturbed shallow pond margins is probably the best way to find the species, they are easily seen and will usually be found in numbers.
3.7-5.6 mm. Elongate, subcylindrical and slightly broadened towards the apex, glabrous and entirely black or with dark brown appendages. Head transverse and rather flat, frontoclypeal suture obsolete or very weak, clypeus obtusely angled about the eyes , smooth, finely punctured and bisinuate anteriorly. Pronotum transverse and convex, broadest across obtuse posterior angles and narrowed to obtuse anterior angles, apical and basal margins curved, lateral border very narrow, basal border weak and widely interrupted medially. Pronotal surface with dual punctures; larger, evenly spaced punctures and more numerous smaller punctures. Scutellum elongate; constricted and almost parallel-sided in the basal half then narrowed to an acute apex. Elytra weakly curved from obtuse shoulders to a continuous apical margin, striae well-defined, punctured and slightly crenulate, interstices flat and very finely punctured, lateral margin very narrow throughout. Basal segment of the middle and hind tarsi slender and at least as long as the corresponding tibial spur, basal segment of hind tarsi as long as the next three combined. In males the median tubercle on the head is usually well-defined, the pronotal punctures are sparser when compared to females, and the metasternal plate is concave. In females the head is almost smooth and the metasternum is flat.
Liothorax plagiatus (Linnaeus, 1767)
This species has a very wide Palaearctic distribution; it is widespread and locally common across Europe from Spain to Greece and north to the UK, Denmark and Southern Scandinavia, although absent from a few countries e.g. Italy and Macedonia. To the east it reaches Siberia, the far east of Russia and China, and it is widespread in Turkey, Syria, Lebanon, Jordan, Iraq, Israel, and Tunisia. In the UK it is very local and more or less exclusively coastal, occurring sporadically from the Humber estuary to Cumbria; it is common in North Kent and South Wales but otherwise very local and scarce. This is essentially a wetland species; in Europe it is associated with well-vegetated freshwater margins, agricultural land, permanently damp grassland and floodplains as well as coastal dunes and beaches while in the UK it occurs on dune slacks and sandy estuaries and is sometimes common among matted vegetation and algae in salt marshes and tidal creeks. Adults are present year-round, they overwinter among decaying vegetation or in the soil and are active from March until October or November, peaking in abundance during May and June but rarely seen during the warmest parts of summer, and the new generation appears in the autumn. The species is not associated with dung; both adults and larvae are saprophagous, feeding and developing among decaying vegetation although Jessop states ‘with small fungi growing in damp hollows in sand hills’, and in northern Europe larvae often occur among decaying vegetation and algae in salty coastal marshes. Adults are often common or even abundant where they occur, they fly in warm weather and sometimes swarm but otherwise may be found under stones or debris, where they often burrow into the soil, or by sieving decaying vegetation, especially on beaches or dunes where it has been partially buried by wind-blown sand.
3.0-5.0 mm. Elongate, convex and subcylindrical, glabrous and shiny. Body black, usually with a weak metallic reflection, clypeal margin and lateral pronotal margin narrowly brown, elytra often with an elongate red patch on the disc, appendages dark brown to almost black, usually with paler tarsi. Head transverse and proportionally large, clypeus variably rugose, obtusely produced and rounded in front of flat eyes and weakly sinuate medially, vertex and frons finely but not densely punctured throughout. Pronotum transverse, lateral margins strongly bordered and straight, almost parallel-sided, apical and basal margins curved and without borders, surface smoothly convex; without a median longitudinal impression, with dual punctures; larger and shallow punctures which tend to be sparse on the disc and more numerous laterally, and much smaller punctures which are more numerous and more evenly distributed. Scutellum narrow, almost parallel-sided in the basal half, triangular and pointed apically, microreticulate and very finely punctured. Elytra oval and only slightly dilated from rounded shoulders to a continuous apical margin, lateral margin very narrow throughout, about as wide as a discal stria, all striae narrow and finely punctured to the apex, interstices flat and very finely punctured. Basal segment of the middle tarsi shorter than the longer tibial spur. Basal segment of the hind tarsi longer than the following three combined and shorter than, or at most as long as, the longer tibial spur. Males may be distinguished by the more distinctly raised ridge on the head, more sparsely punctured pronotum and concave and finely pubescent metasternal plate.