Lithocharis Dejean, 1833
This large and cosmopolitan genus includes more than 100 species (although it is widely accepted that many of these will eventually be assigned to other genera) but is it much less diverse in northern temperate regions; the combined Palaearctic, Oriental and Australian regions include 23 species and 9 species (of which 2 are adventive) occur in North America. Beyond this they are diverse in the Northern Neotropical region, South Africa and are present on many of the oceanic islands. The group occurs throughout the tropics and the Western Palaearctic fauna probably originated from either tropical Africa or the Oriental region. Many species have wide and overlapping distributions, especially in the Eastern Palaearctic and Oriental regions, and so some countries are diverse e.g. 7 species are known from Singapore, but this probably reflects research efforts much more than true diversity and so the number of undescribed species is probably large. Of course some species are endemic to small areas e.g. L. preangerana Cameron, 1936 from Java, or L. botriangulata Assing, 2015 from Sumatra, and some have restricted distributions e.g. L. subochracea Coiffait, 1966 from Yemen, North Africa and the Canary Islands. Some have been widely transported with trade in agricultural products etc. and are now more-or-less cosmopolitan, while a few others e.g. L. sororcula Kraatz. 1859, which is widespread in the Palaearctic, Oriental regions and has been reported from Australia and South America, are likely to become so. This obviously implies that other species may eventually occur in Europe. At present the Central European fauna includes only 2 species; both are near-cosmopolitan in distribution and both extend into the UK, see below. In general they species are associated with decaying plant material in a wide range of terrestrial habitats; some are synanthropic or partly so and this has facilitated their international dispersal. So far as is known all species fly well and many swarm and disperse by this means, many are attracted to light and well placed traps may attract a range of species, this has greatly added to the known diversity.
Lithocharis nigriceps 1
Lithocharis ochracea 1
Lithocharis nigriceps 1
Regarding our UK species; they are small, 3.5-4.0 mm, flattened and drab-coloured insects, usually with the head black and the body and appendages otherwise light brown or with the abdomen a little darker. The dorsal surface is dull due to dense and fine punctation and short recumbent pubescence. Head slightly elongate with large and weakly protruding eyes and long rounded temples, genae much shorter than the eyes and converging anteriorly, labrum rounded anteriorly and with a single median tooth. Mandibles long and sharp; the right with 4 medial teeth and the left with 3, penultimate maxillary palpomere expanded from the base and rounded apically, as long as and a little wider than the previous segment. Antennae filiform, with all segments elongate and the basal segment shorter than the following 2 combined. Pronotum slightly elongate’ widest anteriorly and slightly narrowed to rounded posterior angles, anterior angles obtuse and apical margin produced medially, surface densely but discretely punctured and with scattered larger setae, especially towards the margins, lateral margins bordered; this is visible from above only towards the base, from the basal third or so it curves under the side margin to the anterior angles. Scutellum triangular and relatively large. Elytra slightly wider and much longer than the pronotum, weakly dilated from rounded shoulders to rounded angles and recurved apical margins, surface a little more strongly and densely punctured than the pronotum, with regular backwardly arranged pubescence and several long setae near the shoulders and suture, without any trace of striae. Abdomen smoothly curved laterally and broadest about the middle, basal tergites strongly bordered and the fifth (visible) tergite much longer than 1-4. In males there are tufts of setae along the apical margin of the seventh sternite and the eighth is strongly excised. Legs long and robust, with broad, unarmed femora and tibiae only slightly expanded from the base. Front tibiae weakly excavate near the base, all tibiae with weak and hardly noticeable apical spines. Tarsi 5-segmented, the basal segment of the middle and hind tarsi about as long as the terminal segment, basal segments of front tarsi weakly expanded (a little more so in males) and with a fine longitudinal dorsal groove. Claws smooth and expanded but not toothed at the base.
Superficially similar to several other UK genera but easily distinguished as follows. In Pseudomedon the eyes are smaller and the body is uniformly black. Hypomedon are smaller, < 3mm, with larger punctures and strong microsculpture to the head and pronotum. In both Sunius and Medon the pronotum is shiny and not densely punctured and the head either has a mixture of small and larger punctures (Medon) or small punctures that are sparse and well separated.
Our UK species can be separated as follows:
Eyes slightly longer than the temples. Pronotum finely punctured throughout. Eighth sternite in males with a group of long setae either side within the apical emargination.
Eyes slightly shorter than the temples. Pronotum with a narrow and unpunctured median line. Eighth sternite in males with a several short black setae in the centre of the apical emargination.
Lithocharis nigriceps Kraatz, 1859
This is the most common and widespread member of the genus; it is locally common and often abundant throughout the Palaearctic region from Europe to China, Korea and Japan and recorded from the Azores, India, Sri Lanka and Sumatra, it is thought to be native to Asia (probably Sri Lanka) and to have been transported with trade to other parts of the world; it is now widely established in North America and Australia and is recorded from various countries in the Southern Hemisphere including Tropical and southern Africa, New Zealand and Reunion. In Europe the species has spread steadily since the 1940s and is now generally common from the Pyrenees to the Black Sea in the south and to the UK, all the Baltic countries to the far north of Sweden and Finland. It was first recorded from the UK in 1955 and is now common across southeast and central England and Wales, and widespread but very local further north to the Scottish Highlands and in Northern Ireland. Adults occur among decaying vegetation in the wild but the usual habitat is semi-synanthropic, in cultivated agricultural or horticultural products or among compost or decaying piles of cut grass in gardens etc., they are often common in old straw or hay bales left out in fields and may occur in large numbers in stored straw and dung mixtures. In Europe they are widely eurytopic, occurring in most habitats from woodland and grassland to wetland margins and dunes etc. Adults are present and active year-round and population peaks tend to occur during spring and late summer. Adults may be sampled by sieving suitable material at any time, they fly well and, at least during the warmer months may occasionally appear by sweeping during the evening and sometimes come to light in numbers.
Lithocharis ochracea (Gravenhorst, 1802)
Native to the Western Palaearctic region and with a mostly central and northern distribution in Europe, this species has become established in various parts of the world; it was first detected in the United States in at the turn of the 20th century and has become widespread although mostly near the Atlantic and Pacific coasts, and it is established and widespread in South Africa. In Europe it is common though very local from France to Italy and Austria and north to the UK and reaching the Arctic Circle in Fennoscandia, it is absent from much of eastern Europe although it has recently been recorded from Greece and there are records from the Black Sea coast. The UK distribution is much the same as the previous species; locally common across southeast and central England and Wales but otherwise scattered and rare further north to the Scottish Highlands and in Ireland. The species also occurs in the same sorts of habitats as nigriceps although it is probably the more common species in wild habitats such as among litter in woodland or grassland. Adults are present and active throughout the year; they peak in abundance from July to September and disperse by flight on warm spring and summer evenings. Sieving or extracting samples of compost etc. will usually produce adults at any time and evening sweeping may produce large numbers as they form dispersal swarms.