Sphodrini Laporte, 1834

Briefly, the Sphodrini includes about 850 species and is a primarily Palaearctic group which is only poorly represented elsewhere; about 15 species occur in North America and the New World fauna otherwise includes about 20 species from Mexico, 8 species occur in the Oriental region and about 20 in tropical Africa (Ethiopia) whereas about 775 species are recorded from the Palaearctic region. The group is usually (or at least, often) divided into 6 subtribes as follows: Atranopsina Baehr, 1982 includes about 100 species, more than 60 occur in Europe, mostly around the Mediterranean, 20 in North Africa, 25 in Western Asia and more further east, and a single species in North America. Despite the high European diversity only a single species, Platyderus depressus (Audinet-Serville, 1821) occurs in the UK, Platyderus Stephens, 1827 is otherwise a large genus with about 100 species recorded from the Palaearctic region, the Mediterranean region is most diverse and 55 species are recorded from the Iberian Peninsula. Calathina Laporte, 1834 is a monophyletic group including the single genus Calathus (see above); various other genera may be found in the literature e.g. Synuchidius or Lindrothius but these are now considered to be subgenera of Calathus. The genus is mostly Western Palaearctic in distribution and the subgenera tend to be restricted; Lauricalathus Machado, 1992 includes about 20 species from the Canary Islands. The UK fauna includes 8 species of 3 subgenera. Synuchina Lindroth, 1956 includes about 100 species of 4 genera, 3 genera are restricted to Japan (16 spp.) and Taiwan (1 sp.) while Synuchus Gyllenhall, 1810 is Holarctic, by far the greatest diversity is in eastern Asia and only 2 species are recorded from North America. The very widespread Eurasian S. vivalis (Illiger, 1798) is the only UK species. Sphodrina Laporte, 1834 includes about 360 species and is primarily Palaearctic in distribution; a single species is known from Mexico and 2 species of Laemostenus Bonelli, 1810 have become widely established throughout the world. Laemostenus includes about 200 species in 12 subgenera, it occurs throughout the Palaearctic region, North Africa and the Near and Middle East and is very diverse around the Mediterranean. The UK list also includes the very widespread western Palaearctic Sphodrus leucophthalmus (Linnaeus, 1758), a very rare and generally synanthropic species that has suffered a recent drastic decline through much of its European distribution, the only other member of the genus, S. trochanteribus Mateu, 1990 is endemic to Yemen. The Palaearctic subtribe Dolichina Audouin et Brulle, 1834 includes about 20 species in 6 genera, it is most diverse in eastern regions but several species are widespread in Europe, notably Dolichus halensis (Schaller, 1783) which occurs throughout the Palaearctic region and extends north into the Baltic countries, but none have been recorded from the UK. Prisosiina Lindroth, 1956 includes the single genus Pristosia Motschulsky, 1865, it contains about 100 species in 5 subgenera, they are restricted to eastern areas of the Palaearctic region and China is particularly diverse, none occur in Europe.

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Platynini Bonelli, 1810

Platynini is a cosmopolitan group of about 2700 species in almost 200 genera, the greatest diversity is in tropical and subtropical regions and the northern hemisphere is relatively poorly represented; about 160 species occur in North America and 600 throughout the Palaearctic region, the UK fauna includes 24 species of 8 genera. As yet no sub-tribal system has been worked out, the limits are far from settled and generic names will be seen to change frequently but our UK species, which are now briefly reviewed, represent large and widespread genera and are typical of much of the wider temperate fauna. In much of the older literature most of our species have at one time or another been included in Agonum Bonelli, 1810, which is likely to be split further, but our species are relatively distinctive and the specific names are fairly stable and so they should soon be recognized. Olisthopus Dejean, 1828 is an Holarctic genus of 21 species, 7 are Nearctic and 14 occur in the Palaearctic region, mostly in western and central regions with only a single species extending to the far east, the widespread European O. rotundatus (Paykull, 1790) is our only UK representative. Sericoda Kirby, 1837 includes 8 species, 3 are Holarctic and 2 occur in Central America, 4 species occur in Asia and 2 in Europe, the Holarctic S. quadripunctata (De Geer, 1774) extends north into Alaska and Newfoundland and in Europe to Fennoscandia and the UK. Anchomenus Bonelli, 1810 is an Holarctic genus of 17 species; 4 are Nearctic and 13 are Palaearctic, a single species occurs in North Africa and 3 in Europe of which the widespread Eurasian A. dorsalis (Pontoppidan, 1763) extends to the UK. The UK species Paranchus albipes (Fabricius, 1796) is a widespread across Europe and Asia. Oxypselaphus Chaudoir, 1843 includes 4 species; 2 from North Africa, a single Nearctic species and a single very widespread Palaearctic species, O. obscurus (Herbst, 1784) which is common in the UK. Agonum Bonelli, 1810 includes more than 250 species included in 4 subgenera, more subgenera will be found in the literature but only Agonum s.str., Europhilus Chaudoir, 1859, Olisares Motschulsky, 1865 and Platynomicrus Casey, 1920 are now generally considered valid although many species remain unassigned. The Palaearctic fauna includes about 90 species, most of which occur in western regions, which is slightly larger than the Nearctic fauna, 3 species are endemic to montane areas of tropical Africa and about 15 are Neotropical (Mexico), and among these only 7 are Holarctic. The Palaearctic fauna includes 30 species of Agonum s.str., 16 species of Europhilus, 23 species of Olisares and about 20 unassigned species. Agonum includes the majority of our UK Platyninae with 17 species of 3 subgenera. Platynus Bonelli, 1810 is a very difficult genus to assess; estimates of the number of species range from about 200 to more than 800, and this is because of recent changes to the limits of the genus and a general and constant re-shuffling of the subgenera and species; our single UK species is P. livens (Gyllenhal, 1810), formerly classified within Agonum or Batenus Motschulsky, 1864, and the UK species long-known as P. assimilis (Paykull, 1790) (formerly also in Agonum) is now called Limodromus assimilis (Paykull, 1790).

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Description

In the wider sense the subfamily includes many spectacular colourful and metallic species, these are relatively uncommon in northern temperate regions but a hint of this can be seen in the Palaearctic Agonum sexpunctatum (Linnaeus, 1758) or the Nearctic A. cupripenne (Say, 1823), conversely the subfamily includes many highly adapted cave-dwelling and subterranean species that have reduced eyes and wings and lack pigments, such species are diverse around northern Mediterranean regions and especially so in Italy and Spain, by contrast the UK fauna are a rather drab assemblage-although it does include Agonum sexpunctatum and the rather less spectacular but nonetheless attractive A. muelleri (Herbst, 1784)- and most are black, brown or bicoloured with the same. Fortunately our UK species are rather easily distinguished among our wider carabid fauna on obvious, though sometimes comparative, morphological characters; the mandibles are sharp, more-or-less symmetrical and lack a setiferous puncture on the external margin, the head lacks deep furrows and the terminal maxillary palpomere is at least as long as the penultimate segment, the penultimate labial palpomere has only one or two setae, the elytral epipleura are not ‘crossed’ subapically and the apex is rounded rather than truncate. These characters will exclude most of our carabids but will need to be examined carefully; the head has two setiferous punctures inside each eye, the same as our Pterostichinae, but Platyninae lack the ‘crossed’ epipleura and have the pro-tibiae narrow and sub-parallel towards the apex. The groups are keyed out here but with experience most species, or at least genera, will become obvious in the field; most have a narrow forebody and relatively broad elytra-rather like large versions of Bembidion Latreille, 1802-and several genera such as Calathus, Laemostenus, Sphodrus and Synuchus may be recognized by the serrate claws coupled with the general appearance. In most keys the genera of both tribes are included together because it is easier to separate them on gross morphology than by initially separating the tribes; there are fundamental differences in the structure of the genitalia and in Platynini the apical margin of the prosternal process is margined whereas in Sphodrini it is not. Our species are small to medium sized carabids, 4.5-28.0mm, they have prominent convex eyes and in most the head is produced anteriorly, the antennae are long and slender and pubescent from the third or fourth segment, the pronotum is often smooth or only shallowly sculptured, in contrast to many Pterostichinae, and varies widely in form i.e. rounded to strongly sinuate laterally and with rounded or sharp posterior angles, and in most it is distinctly wider than the head and narrower than the elytra. The elytra are also very variable but all have punctured striae (very fine in Sphodrus) and simple epipleura, discal punctures present in all but Laemostenus and Sphodrus and in all cases the apices are continuously rounded, never truncate. The legs are long and slender, including the front tibiae which will distinguish the subfamily from Pterostichinae, the front tibiae have a well-developed antenna-cleaning notch on the inner margin before the apex and all tibiae have a single strong spur at the inner apical angle. The tarsi are very variable in form; they may be glabrous or pubescent, various segments may have dorsal or lateral grooves and in males at least the basal pro-tarsomeres are dilated.

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Ecology

The subfamily includes many common and widespread species which should be among the first carabids recorded by the beginner. Calathus fuscipes (Goeze, 1777) and C. melanocephalus (Linnaeus, 1758) are generally abundant in open situations while C. rotundicollis Dejean, 1828 is also common in woodland, and C. erratus (Sahlberg, C.R., 1827) and C. mollis (Marsham, 1802) are common coastal species. Platyderus depressus (Audinet-Serville, 1821) and Synuchus vivalis (Illiger, 1798 are widespread but very local in open situations as well as dry woodland. Oxypselaphus obscurus (Herbst, 1784) and Paranchus albipes (Fabricius, 1796) are common and often abundant in permanently damp situations while Anchomenus dorsalis (Pontoppidan, 1763) is generally common in dry habitats. Olisthopus rotundatus (Paykull, 1790) is locally common on dry heaths and coastal dunes while the generally common Limodromus assimilis (Paykull, 1790) occurs mostly in woodlands but may also be found around wetland margins. Platynus livens (Gyllenhal, 1810) is a very local species of south and central England, it is usually associated with decaying litter in marshes but also occurs in damp woodland. The generally rare and sporadic Sericoda quadripunctata (De Geer, 1774) inhabits coniferous woodland and often occurs among burnt wood or under logs following forest fires. Sphodrus leucophthalmus is a very rare synanthropic species, it was formerly widespread in cellars and stores etc. where it specialized in predating Blaps, but has suffered a recent and drastic Europe-wide decline and has not been recorded from the UK in recent decades. Laemostenus terricola (Herbst, 1784) is largely subterranean and often associated with mammal nests or runs but also occurs under stones in sandy areas and under bark and has been recorded from basements and cellars, L. complanatus (Dejean, 1828) is more synanthropic, usually in stores and cellars among stored produce, but also occasionally outside, both species are very local and generally rare. Our species of Agonum are mostly associated with wetland habitats and a few e.g. A. marginatum (Linnaeus, 1758), A. thoreyi Dejean, 1828, A. fuliginosum (Panzer, 1809) and A. emarginatum (Gyllenhal, 1827) are widespread and very common. A. muelleri (Herbst, 1784) may also occur in wetland situations but is more eurytopic, occurring also on pasture, agricultural land and even domestic gardens. Several others are more local but nonetheless should appear by careful searching e.g. A. gracile Sturm, 1824, A. piceum (Linnaeus, 1758) and A. micans (Nicolai, 1822). Our other species are more local and generally rare e.g. A. ericeti (Panzer, 1809) occurs mostly in the north but is also present in Dorset and Hampshire, A. gracilipes (Duftschmid, 1812) is only occasionally recorded from continental vagrants and A. chalconotum Ménétries, 1832 has not been recorded since the early twentieth century and is thought to be extinct in the UK. The splendid-looking A. sexpunctatum (Linnaeus, 1758) is a very local and rare wetland species of southern England although there are older and much more widely distributed records.

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From the above it should be obvious that all the usual sampling methods can be employed to fine these species; searching at night will often produce an abundance of material, whether on open grassland, parkland pathways, woodland or wetland marginal situations, many species are also diurnal and may be seem running among tussocks or across damp soil, and searching under logs and among debris will often be successful, more especially as some species e.g. Anchomenus dorsalis, Paranchus albipes, Agonum fuliginosum and A. thoreyi, often appear in aggregations under logs etc. Many species occur throughout the year but spring and early summer are probably the best times for general sampling; some wetland species must be observed in the wild in order to appreciate how abundant they can be, which is why some make ideal subjects for studies into population dynamics, and which is also why pitfall trapping must be done very carefully as in such situations it can be destructive when large numbers of beetles are trapped. The same was formerly true of Anchomenus dorsalis which occurred in large spring aggregations during the 1970’s and 1980’s on farmland in west London but now has either vanished from many of its former haunts or occurs only in small numbers. Flight capacity and wing development varies across the group but in general many common species are usually quick to invade new sites.