LICININAE Bonelli, 1810
Very distinctive medium-sized ground beetles, most are local and rare and will be found by chance, only Badister bullatus and Chlaenius vestitus are common and widespread.
This large subfamily of ground beetles is represented in the UK by 4 tribes, all of which are variously classified as subfamilies of the Carabidae Latreille, 1802 or as tribes within a broadly inclusive Harpalinae Bonelli, 1810, these tribes are Oodini La Ferte-Senectere, 1851, Panagaeini Bonelli, 1810, Chlaeniini Brullé, 1834 and Licinini Bonelli, 1810. The scope of each will also be found to vary widely in the literature e.g. Oodini includes between 200 and 300 species depending on how it is defined and it seems unlikely that the extent of these tribes will be determined until a thorough molecular analysis has been performed, in each case therefore we have used a conservative estimate of the size of each tribe based mostly upon northern temperate faunas, which is very likely to be widely underestimated as the various tribes are by far most diverse in tropical regions. The group is likely to be proved artificial although members of the 4 tribes display similarities in genitalia, male protarsal and larval structure.
OODINI LaFerté-Sénectère, 1851
Oodini typically includes about 270 species in 32 genera and is cosmopolitan in distribution, the greatest diversity is in tropical Africa and northern temperate faunas tend to be small. They are thought to be most closely related to the Chlaeniini, the loss of pubescence being due to the evolution of a semi-aquatic lifestyle, but are distinguished by the form of the eighth elytra, this is much deeper than the seventh and raised laterally onto the ninth interstice to form a narrow ridge which extends around the apex almost to the suture, and the epipleura are ‘crossed’ with the margins twisted before the apex, as seen in many pterostichines, this elytral structure is common to all genera within the tribe and will distinguish it from other carabids generally. They are otherwise very typical carabids; medium sized, drab and often suggestive of Amara but with a single setiferous puncture beside each eye and only one or two setae on the inner margin of the penultimate labial palpomere. The mandibles are sharp, only weakly curved and lack a pore in the lateral scrobe, the eyes are usually large and convex and the antennae long and slender. In most the pronotum is broadest at the base, moderately flattened and with at most only shallow and weakly-defined basal impressions, the lateral margins are not or only narrowly explanate and lack sensory setae. Most are elongate-oval and near-continuous in outline, many are entirely dark or with the appendages variously paler although some have weak patterns or red flecks to the pronotum and some are metallic, sometimes vividly so but usually only weakly. The elytra are oval and continuously-rounded apically and all have narrow and variously punctured striae, many have an abbreviated scutellary striole and in some genera there is a strong puncture at the base of the first stria, there is a small shoulder tooth in many species and most lack dorsal punctures. On the ventral surface the metepimeron appears as a small scale-like structure overlying the base towards the side of the first abdominal ventrite. Most species are strongly hygrophilous, occurring among dense vegetation, decaying wood or other organic matter beside standing water.
The tribe is represented in Europe by 5 species of 3 genera. Lachnocrepis prolix (Bates, 1873) is a widespread Palaearctic species that extends west into parts of central Europe. Lonchosternus LaFerte-Senectere, 1851 includes 2 European species; L. angolensis (Erichson, 1843) occurs in North Africa and a few northern Mediterranean areas while L. hispanicus (Dejean, 1826) is restricted to parts of Portugal, Spain and North West Africa. Oodes includes about 50 species and is Holarctic in distribution, extending south into tropical Africa and the Oriental and Australasian regions but only two very widespread though local Palaearctic species of occur throughout most of Europe; O. helopioides (Fabricius, 1792) extends north into Fennoscandia and the UK while O. gracilis Villa & Villa, 1833 is more sparse in northern areas; it is absent from the UK and in Fennoscandia known from only a single site in Sweden.
PANAGAEINI Bonelli, 1810
Panagaeini, sometimes known as hairy ground beetles, includes almost 300 species, it is represented in all the major biogeographical regions and is by far most diverse in tropical areas; of the Holarctic fauna about 40 species are Palaearctic and a further 4 occur in North America. The group includes some well-known tropical genera e.g. the Afrotropical Tefflus Leach, 1819, with about 15 species, includes a few large, >50mm, and impressive nocturnal predators that can run rapidly and inflict a serious bite (although a common name for the genus is ‘peaceful giant ground beetles’), they are entirely shiny black and very finely pubescent, strongly constricted and with convex elytral interstices that gives them a characteristic appearance. Most species of the tribe are medium sized, elongate and discontinuous in outline and many have a characteristic colour pattern of large red or yellow elytral maculae contrasting with a darker ground colour, all members of the tribe are pubescent, at least to some extent and usually substantially so, and most are strongly punctured and sculptured dorsally, a general feature of most species is a more-or-less quadrate pronotum being widest about the middle, strongly narrowed to the front and rear and lacking any well-defined basal fovea, but some tropical species are very atypical e.g. species of the Neotropical genus Brachygnathus Perty, 1830 are only very finely pubescent, appearing almost glabrous, have an elongate and strongly foveate pronotum, rounded, entirely deep metallic green elytra and lack strong dorsal punctures or sculpture. The familiar Panagaeus Latreille, 1802 includes 15 species of which 7 occur in the New World and 8 in the Palaearctic region although most are distributed in Asia and only 2 very widespread species extend west into Europe, including the UK.
Both Panagaeus cruxmajor (Linnaeus, 1758) and P. bipustulatus (Fabricius, 1775) occur throughout Europe and extend north into southern Fennoscandia and the UK, both are very local and not particularly common in central and northern areas and both are rare in the UK. Both species occur year-round, P. cruxmajor is associated with densely-vegetated wetlands while the more frequent P. bipustulatus occurs on dry grasslands etc. exposed to the sun. Both are very distinctive among our fauna and may be recognized by the size, 6.5-9.0mm, and colour; entirely black with four variously-developed red elytral maculae. Confirmatory features include 2 sensory setae beside the protruding and very convex eyes, anteriorly produced head with long palps and antennae, rounded and strongly punctured pronotum, strongly punctured elytral striae, and both have dense dorsal pubescence. In common with Oodini and Chlaeniini (but not Licinini) the elytral epipleura are ‘crossed’ before the apex. Both sexes are fully winged and males may be distinguished by dilated basal pro-tarsomeres.
CHLAENIINI Brullé, 1834
Chlaeniini includes >1000 species in about 20 genera and occurs worldwide although the greatest generic and specific diversity is in tropical regions of Africa and the Oriental region, the tribe is variously classified among up to 10 subtribes but the limits of most are uncertain and the situation remains to be settled. A modern concept places all but 2 genera within the Chlaeniina Brullé, 1834, with Callistina Laporte, 1834 including only the Old-World Callistus Bonelli, 1810 (3 spp.) and Callistomimus Chaudoir, 1872 (about 45 spp.). The majority of species are included in the large genus Chlaenius Bonelli, 1810; more than 860 described species are divided among about 60 subgenera (some of which are variously classified as full genera), many of these are endemic to certain areas and the genus forms the majority of the fauna in northern temperate regions e.g. 51 species of 10 subgenera occur in North America and these are the only representatives of the tribe to occur there, and the European fauna includes about 30 species of 7 subgenera. The European fauna also includes 7 species of Dinodes Bonelli, 1810, 2 species of Epomus Bonelli, 1810 and Callistus lunatus (Fabricius, 1775). The remaining genera are mostly small and restricted to Old World tropical regions e.g. the monotypic Ectenognathus Murray, 1958 occurs on the west coast of Africa. Most species may be recognized by the densely punctured and pubescent dorsal surface (chlaen means ‘cloak’ in Greek and refers to this dorsal pubescence), all are medium sized ground beetles and many are vividly metallic or brightly patterned. Our UK species are very typical of the tribe as a whole, they have sharp mandibles, a single supra-orbital puncture and ‘crossed’ elytral epipleura; some species of Harpalus Latreille, 1802 are also pubescent but here the third antennomere is densely pubescent while in Chlaenius it is more or less glabrous, species of Poecilus Bonelli, 1810 are also brilliant metallic and have ‘crossed’ epipleura but the dorsal surface lacks the pubescence seen in the present group. Confirmatory characters for Chlaenius are size, 9-13mm, lack of a sensory seta on the lateral margin of the mandibles, rounded elytral apices and elytral sculpture. So far as the UK fauna is concerned they may be readily recognized by the general appearance.
Most of the species are adapted to either warm or cold conditions and are terrestrial, living in damp or wetland marginal habitats, but a few inhabit woodlands and open dry situations. Five species of 2 genera have been recorded in the UK. Callistus lunatus is a very local and generally scarce species occurring throughout Europe and Western Asia, adults are thermophilic and occur year-round on open dry grassland on sandy and chalky soils and in southern areas often occur in vineyards or on agricultural borders. The species was formerly very local in south-east England but declined drastically after 1930 and has not been recorded since the 1950s. Callistus cannot be mistaken among our fauna; the dorsal surface is densely pubescent and the elytra are yellow with 3 black maculae. Although obviously different from Chlaenius it also differs in having the third antennomere pubescent. Four species of Chlaenius have been recorded from the UK but the brilliant metallic C. nitidulus (Schrank, 1781), formerly recorded around seepages below a few cliffs on the south coast of England, has not been found since 1930, it is otherwise widespread in Europe, extending north to southern Fennoscandia and occurring in wetlands of all kinds, gravel pits and gardens as well as in coastal situations. C. tristis (Schaller, 1783), our only black member of the genus, is a widespread though very local Eurasian species of wetlands and acid moorlands, it was formerly known from England (East Anglia) but since 1900 has been recorded only from North Wales. C. vestitus (Paykull, 1790) is locally common in wetlands throughout Europe, North Africa and Western Asia; it remains locally common in the south or England and Wales and may be very abundant in undisturbed wetland situations. It is easily identified by the bicoloured elytra; metallic green with pale creamy margins. C. nigricornis (Fabricius, 1781) is widespread and generally common on the continent but here is very local across England, Wales, Ireland and the south of Scotland, it is thermophilic and associated with wetlands and damp grassland, often in coastal situations. Adults are brilliant metallic but may be distinguished from C. nitidulus by the dark third antennomere.
LICININI Bonelli, 1810
Licinini includes about 240 species in 23 genera and 4 subtribes and is distributed worldwide, more than 60% occur in the Northern Hemisphere and of these about two thirds are Palaearctic, southern temperate regions are also diverse although the Neotropical region is only very poorly represented and as the various genera tend to be restricted to certain areas each region has a very distinctive fauna. Dichrochilina includes about 30 species of Dicrochile Guérin-Méneville, 1846 and is restricted to Australasia and more particularly New Zealand. Dicaelina Laporte, 1834 includes about 45 species of 2 genera and is Holarctic. Lestignathina Ball, 1992 is a widespread Old World group of about 60 species of 10 genera. Licinina Bonelli, 1810 includes about 100 species in 9 genera and occurs worldwide but the greatest diversity (>80%) is in the Northern Hemisphere; 14 species are recorded from the Nearctic region and 68 from the Palaearctic while 5 species are Neotropical, 3 are Afrotropical, 11 are Australasian and 4 are Oriental. Badister Clairville, 1806 is a widespread genus of about 50 species, most occur in temperate and boreal regions of the Northern Hemisphere and 27 are recorded from the Palaearctic region, 10 of these occur in Europe and 7 extend to the UK. Licinus Latreille, 1802 is an indigenous Palaearctic genus of about 30; 14 occur in Europe and 2 of these extend to the UK. Members of this tribe are closely related to the previous groups but have unique mandibular structure and lack ‘crossed’ elytral epipleura. The common name of ‘notch-mouthed Ground Beetles’ refers to the deeply emarginate or grooved labrum. Two subtribes are represented in the Nearctic region by 62 species of 3 genera, one of which is indigenous, and all subtribes occur in the Palaearctic region, 3 are represented in Europe by 31 species of 5 genera and of these 9 species of 2 genera extend to the UK.
The biology of many species is unknown but all species studied so far are terrestrial predators, specializing in both adult and larval stages to feed on molluscs, more generally on snails which they attack by biting through the shell rather than through the operculum as in some other ground-beetle groups e.g. Cychrus. This is facilitated by the asymmetric mandibles; the shell is cut along the upper part of a whorl with slow bites made at an angle (an action like that of an old-fashioned can-opener), this cut extends across to the lower part of a second whorl and continues to form a wide hole across several whorls, a process known as ‘shell crushing, which seems to be an instinctive behaviour that can be adapted to shells of differing sizes. The modified shape and size of the mouthparts i.e. shorter and broader mandibles which are stronger and a cleft labrum which is movable and can slide under the broadly excavate clypeus, may be an adaptation to deal with the dextral spiral seen in most terrestrial gastropods. A few species are associated with wetlands but the majority occur in open and damp habitats; calcareous grassland often being rich in species.