BROSCINAE Bonelli, 1810
Includes two British species. Broscus cephalotes is widespread and common in coastal habitats, while Miscodera arctica is a much rarer montane species.
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Introduction
This subfamily includes more than 290 species in 35 genera and is distributed in temperate regions worldwide although the Nearctic fauna is tiny with 4 species of 4 genera of which one is introduced. All species are included in the single tribe Broscini Hope, 1838 which is divided into five subtribes as follows. Axonyina Roig-JuÅ„ient, 2000 includes 5 species of 3 genera from the Palaearctic (see below), Iran and Mexico. Broscina Hope, 1838 is Holarctic, extending south into the Oriental region; it includes about 75 species in 9 genera. Nothobroscina includes about 90 species in 10 genera from the Australasian and Neotropical regions (a single species from Chile). The Neotropical Barypodina Jeannel, 1941 includes about 25 species if two genera. Creobiina Jeannel, 1941 includes about 95 species of 11 genera from the Australasian and Neotropical regions. With the exception of North America and Africa most regions have a diverse fauna, particularly Australasia with about 180 species; the fauna of New Zealand includes three small genera and about 75 species and subspecies of the endemic genus Mecodema Blanchard, 1853, while that of Australia includes about 110 species of 10 genera. The Neotropical region has about 30 species (so far described) and the Oriental has 5 species. The Palaearctic fauna includes two species of the genus Broscodes Bolívar y Pietain, 1914, one is endemic to India and the other is widespread in eastern Asia, and they are the only representatives of the subtribe Axonyina Roig-JuÅ„ent, 2000. The subtribe Broscina Hope, 1838 is much more diverse with about 85 species (some are represented by several subspecies) of 8 genera. Broscodera Lindroth, 1961 includes three species from China and one from North America. Broscosoma Rosenhauer, 1846 includes about 40 species, the majority occur in China but the genus extends to Japan and there is a single European member, B. baldense Rosenhauer, 1846, endemic to Italy. Broscus Panzer, 1813 includes about 30 species in three subgenera, most are Asian but six occur in Europe and a further three are endemic to the Canary Islands. Chaetobroscus Semenov, 1900 includes four species and is widespread in eastern Asia. Craspedontus Schaum, 1863 includes three central Asian species. Eobroscus Kryzhanovskij, 1951 includes three central Asian species and Kashmirobroscus Schmidt, J., Wrase & Sciaky, 2013 includes 2 species endemic to Pakistan. The monotypic Miscodera Eschscholtz, 1830 is Holarctic.
Ecology
Species are often associated with wetland marginal habitats, including coastal dunes and shores, or damp woodland and many occur at higher mountain altitudes. They are usually nocturnal predators and while many are fully-winged they are rarely observed to fly, by day they rest under debris or burrow into soft soil or sand, and they may occur in large numbers.
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Description
Members of this subfamily may be recognized from the pedunculate body form; the scutellum being placed on the mesonotum behind the pronotal base and (mostly) in front of the base of the elytra. The anterior tibiae are smooth externally which will distinguish them from the Scaritinae Bonelli, 1810 which also have the pedunculate body form but the anterior tibiae are strongly toothed along the outer margin. Most species are medium sized, 6-25mm, and rather parallel-sided, glabrous, dull black or faintly metallic blue or green and of a characteristic general form. The head is proportionately large and only a little narrower than the pronotum, with convex and prominent eyes, a well-developed fronto-clypeal suture and, often, prominent and projecting mouthparts, there is a single supra-orbital seta and the antennae are pubescent from the third or fourth segment. The mandibles are generally broad and curved to a sharp apex, often asymmetric and sometimes expanded laterally, and with a seta the lateral scrobe, the palps are of moderate length and narrow or only weakly thickened, usually sub-cylindrical and variously rounded or truncate apically. The pronotum is widest at or in front of the middle, laterally bordered and strongly narrowed to a straight basal margin, the surface is moderately to very strongly convex and only very finely punctured, the cuticle is often wrinkled and there may be larger punctures anterior to the basal margin, in many there is a median longitudinal furrow but basal fovea are usually absent. The elytra are convex, elongate and weakly to strongly curved laterally, the shoulders are rounded or sloping and the apical margin is continuously rounded, there is no basal margin and the striae are very variable; sometimes almost missing or represented by rows of small punctures but in exotic species they may be deeply impressed and emphasized by strongly carinate interstices, the basal margin often has stronger punctures, sometimes arranged in a transverse row, and the interstices are usually flat to weakly convex and unadorned; in some exotics they have a row of elongate tubercles on some interstices, reminiscent of Carabus monilis. The legs are long, robust and of typical carabid form, the anterior tibiae have a deep antenna-cleaning notch internally before the apex and a single apical spur, the middle and hind tibiae are narrow and only moderately widened to the apex and each has a pair of spurs at the inner apical angle. Two species occur in the UK, they are easily identified by the form of the pronotum and the anterior tibiae and as they are very different in size with no overlap, specific identification should always be certain.
Miscodera arctica (Paykull, 1798)
This is a Holarctic and mostly Boreo-montane species; in Europe widespread in the north with relict populations from past glacial events in the Italian and Swiss Alps and from Moravia, the distribution is otherwise continuous from northern Fennoscandia up to about 62 degrees north, across northern Asia to the Bearing sea, it is widespread in Canada and North America from Alaska to Newfoundland and fossils from 2.0-2.5Ma have been found in Greenland. In the UK it is widespread though very local in Wales, northern England and the Scottish Highlands, there are a few records from the Western Isles and it has recently been discovered at several coastal sites in northwest Ireland, it is an excellent flyer and may disperse over long distances and so might be expected occur in any suitable habitat within its range. Here the typical habitat is open and well-drained gravelly or sandy substrates on heaths and upland slopes, in northern Europe often in pine woodland, alpine grassland, on shaded parts of heaths or on long-established and overgrown dunes, usually on sandy or gravelly soils and often in association with other carabids, especially Notiophilus aquaticus (Linnaeus, 1758), Curtonotus alpinus (Paykull, 1790) and Cymindis vaporariorum (Linnaeus, 1758). Adults occur year-round; they overwinter in the soil are active over a very long season, from February until November, they are seldom seen in the open and generally remain hidden among moss or under stones and are almost always associated with species of Byrrhus or Cytilus (Byrrhidae), the larvae of which are thought to be its main prey items. In northern Europe breeding occurs in late summer and autumn and larvae are thought to overwinter and develop through the following summer as freshly eclosed adults have been found in July and August.
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A small, 6.5-8.0mm shiny black or bronze carabid with pale brown appendages, unmistakable due to the pedunculate body form and unmodified anterior tibiae. Head and pronotum smooth and unpunctured but for a transverse band of punctures across the pronotal base linking the lateral constrictions. Frons with a single supra-orbital puncture, eyes convex and prominent and antennae pubescent from the fifth segment. Pronotum finely bordered laterally, anterior angles rounded. Elytra widest behind the middle, with prominent shoulders and rounded laterally to a continuously rounded apical margin, each with three or four strong punctures across the base and punctured striae which fade laterally and apically. Anterior tibiae only moderately widened towards the apex, with a deep antennae-cleaning notch and a long apical spur, externally with five short teeth towards the apex but otherwise smooth. Male basal pro-tarsomeres dilated.
Broscus cephalotes (Linnaeus, 1758)
This generally common species occurs throughout temperate central and Western Europe and Asia Minor, extending east into western Siberia and north to the UK and central Fennoscandia, it is a common coastal species but also occurs inland; in north on sandy or loamy grassland and agricultural land, especially among root crops, but further south also on heavier clay soils in a range of habitats. It was first discovered in North America in 1987 from Nova Scotia and has since become established on sandy beaches in western Canada and the United States. Here it is generally common around the UK coasts, including all the islands north to Orkney, and there are inland records from the Thames and Severn valleys, East Anglia and the midlands. Adults are present year-round, they are active from early spring until late autumn, peaking in July and august, they usually occur on beaches between the strandline and sparsely vegetated dunes and are nocturnal, spending the day under debris or in the sand, often in groups, and may be found by digging or sieving sand or searching at night when they roam the sand in search of prey. They are known to feed on a very wide range of insects and other arthropods including sand hoppers and worms and in captivity will consume almost anything presented. Reproduction occurs in late summer and autumn and these adults will go on to overwinter in the soil but most will die off before the spring, each female will dig a series of deep burrows and deposit an egg into the base of each one but there is no further parental care, oviposition continues from late July until September and the earliest larvae are active from late August, these will develop through the winter and spring to produce adults in early July but later larvae may continue developing through the summer to produce adults in the autumn or they may even overwinter twice to produce spring adults. The cycle from egg to adult is usually completed within the burrow excavated by the female. Adults are readily predated by birds and so remain hidden during the day but they are also eaten by amphibians, rodents and hedgehogs by night and so the first signs of the beetle may be fragments of elytra etc. among the sand.
The large size and distinctive habitus make this species unmistakable among our UK fauna. 17-22mm. Entirely dull black without any metallic reflection, antennae, palps and tarsi often a little paler, especially towards the apices. Head and pronotum finely punctured and wrinkled, often strongly so on the vertex behind the eyes and towards the base of the pronotum. Head proportionally large, with convex and prominent eyes and long temples that are constricted some distance before the pronotal margin. Labrum transverse, mandibles proportionally very large, each with a single seta on the lateral scrobe, antennae pubescent from the apex of the fourth segment; the second segment about half as long as the third. Pronotum only moderately convex, widest in front of the middle and characteristically narrowed to perpendicular posterior angles, lateral margins complete to the base and each with two long setae, one near the middle and one in front of the base. Elytra elongate (2:1) with sloping shoulders and gradually widened to the apical third, striae faintly impressed and finely punctured, often obliterated on the disc and towards the sides and apex. Legs long and robust, anterior tibiae with a deep antennal-cleaning notch and a tiny spur on the inner apical angle. Male pro-tarsi dilated.