PTEROSTICHINAE Bonelli, 1810
Includes many common and distinctive species although some are difficult to identify without modern keys, most occur in open or wooded habitats and most are nocturnal.
It is very difficult to keep up with the higher classification of the ‘harpaline’ group of ground beetles; whatever the current status it is likely to change, this should be obvious from the popularity of the group and it is likely to continue changing as molecular data become available. The present group is often classified as a tribe of a much wider Harpalinae but, pedantry aside, it does form a distinct and easily-recognizable assemblage (at least in northern temperate regions) that is relatively well-understood. As discussed here the group consists of 9 tribes and this includes the Zabrini Bonelli, 1810 which is often given equal status to the ‘Pterostichini’ within the Harpalinae (or within the supertribe Pterostichitae, a supertribe of the Harpalinae), 5 of these occur in Europe and two of these, Pterostichini and Zabrini, extend to the UK. Abacetini Chaudoir, 1872 which variously includes between 500 and 800 species in between 31 and 45 genera (depending upon the definition), is a mostly tropical and subtropical group with only about 10% of species in the Northern Hemisphere and 10% in the New World, it is by far most diverse in the Old World tropics and is distributed throughout Africa, southern Asia, and the Pacific region south to Northern Australia; 45 species occur in North America (all but one in the large, >210 spp. and mostly Neotropical genus Loxandrus LeConte, 1853), only two species of Abacetus Dejean, 1828 (a genus of about 450 spp.) extend north into Europe but not the UK. Catapieseini Bates, 1882 is a Neotropical tribe of 2 genera and about 10 species. Chaetodactylini Tschitscherine, 1903 includes about 20 species of the Madagascan endemic genus Chaetodactyla Tschitscherine, 1897. Cnemalobini Germain, 1911 includes only the Neotropical genus Cnemalobus Guerin-Meneville, 1838 with about 35 species from Uruguay, Chile and Argentina. Cratocerini Lacordaire, 1854 includes 4 species of 3 genera; one each from Japan, Australasia and South America. Morionini Brullé, 1835 includes about 85 species in 9 genera, most occur in the Old World tropics; 13 species of 3 genera occur in the New World of which 2 species of the pantropical genus Morion Latreille, 1810 (about 40 spp.) extend into North America, a single species of Morion, M. olympicus Redtenbacher, 1843 occurs in Europe (Cyprus, Greece and the Near East) but none occur in the UK. Microcheillini Jeannel, 1948 includes 2 species of the Madagascan endemic genus Microcheila Brulle, 1834. Drimostomatini Chaudoir, 1872 is
Pterostichus madidus larva
another pantropical group with only very few species extending into northern temperate areas, about 300 species of 31 genera are known but none occur in Europe. The two remaining tribes are very speciose in northern temperate regions and well-known to British coleopterists, various systems of classification will be found and the tribes are prone to splitting e.g. the genus Stomis Clairville, 1806 will sometimes be found in its own tribe, but the following discussion assumes a classification in line with the UK checklist and includes a brief look at the European fauna. The tribes can be identified by the key HERE, which uses morphological characters as a matter of convenience rather than attempting to define anything in phylogenetic terms; it will be seen that the tribes are distinguished by a contrived combination of characters, these work well for the limited UK list (and even so, exceptions need to be made) but soon fail with the wider European fauna.
Pterostichini Bonelli, 1810 includes more than 3000 species in about 150 genera and a variable number of subtribes which will only be mentioned in passing as they tend to be used sporadically in the literature, they occur worldwide but are most diverse in temperate regions, especially in the Palaearctic where there is a diverse fauna extending into the Arctic tundra, the Nearctic fauna is relatively poor by comparison with about 250 species of 12 genera. The European fauna is very diverse and (usually) falls into 4 subtribes; Molopina Bonelli, 1810 is a very speciose and widespread Old-World group of 27 genera; about 85 species of 13 genera occur in Europe and the Mediterranean region is particularly diverse, included is the familiar genus Abax Bonelli, 1810, a single species of which extends to the UK. Myadina Jakobson, 1907 is represented by 2 genera and 2 species in southern Europe. Poecilina Bonelli, 1810 includes 5 European genera and about 75 species. The Holarctic genus Poecilus Bonelli, 1810 includes about 140 species, the majority occur in the Palaearctic region, including North Africa, and about 40 are European, they are most diverse in the south and only 4 species extend north into the UK. The small Western Palaearctic genus Pedius Motschulsky, 1850, formerly included in Pterostichus, includes 4 European species; one is widespread across the Northern Mediterranean region, 2 are island endemics; from Sicily and the Canary Islands, and P. longicollis (Duftschmid, 1812 is widespread in central Europe and extends to the UK. Pterostichina is the largest European subtribe with about 275 species in 6 genera, the majority, >200, are included in the very large genus Pterostichus (which includes more than 2000 species) and 18 of these extend to the UK. The Holarctic genus Stomis Clairville, 1806 includes about 40 species, the majority occur in Asia; 2 occur in North America (one of which is adventive) and only 6 are European, the most widely distributed of which, S. pumicatus (Panzer, 1796), extends to the UK.
Zabrini Bonelli, 1810 includes a small but variable number of genera although one of these, the monotypic Nearctic genus Pseudamara Lindroth, 1968 is now more generally included in the Sphodrini Laporte, 1834. Amara Bonelli, 1810 is a large worldwide genus of more than 600 species in almost 60 subgenera, it is primarily Holarctic with the greatest diversity in the Palaearctic region, to the south it extends to mountainous regions of Ethiopia and into southern China and Indochina, the Nearctic fauna includes just over a hundred species of 11 subgenera and the genus extends south as far as Costa Rica. The European fauna includes about 130 species of 25 subgenera and of these 29 species of 7 subgenera extend to the UK. Curtonotus Stephens, 1828, still widely accepted as a subgenus of Amara, is a Holarctic genus of about 85 species; the greatest diversity is in mountainous regions of Asia, 15 species occur in North America and 12 in Europe of which 3 extend to the UK. Zabrus Clairville, 1806 is a Palaearctic genus of about 120 species, the European fauna includes 64 species, most of which occur in southern regions or mountain areas and many of which have very limited distributions or are endemic to certain areas e.g. the Canaries or various Mediterranean islands, and adjacent areas of northwest Africa are also very diverse but only a single species, the widespread central European Z. tenebroides (Goeze, 1777), extends to the UK.
UK members of this subfamily are very typical carabids and will soon become familiar despite the rather awkward way they key out e.g. all have two setiferous punctures beside each eye except for Zabrus, and all have ‘crossed’ elytral epipleura except for Pterostichus cristatus (Dufour, 1820). Among our fauna Stomis and Abax are unmistakable; species of Poecilus are bright metallic and have a fine longitudinal keel on the three basal antennal segments. Zabrus is large and robust and may be distinguished by the form of the front tibiae. Amara are very distinctive, elongate oval and more or less continuous in outline, many are metallic bronze or green and all lack the dorsal ridge on the basal antennal segments seen in Poecilus. Curtonotus was formerly included in Amara, they are distinguished by the prosternal process being unmargined but all UK species are very distinctive in having the pronotum narrowed towards the base and strongly sinuate laterally before the posterior angles, a condition also seen, but to a much lesser extent, in some Amara. All members of the subfamily are small to medium sized beetles, 4.5-16.0mm, in UK species Poecilus and many Amara are metallic, the rest black or black with pale appendages, all have a mostly unsculptured head, large eyes, and relatively short antennae. The pronotum is very variable, especially in Pterostichus but in most there are well-developed basal fovea. The elytra are rounded apically, they usually have well-impressed and complete striae and most have an abbreviated scutellary stria. All have an antenna-cleaning notch on the internal margin of the front tibia and well-developed terminal spurs. Males are often duller than females and have variously dilated front and sometimes middle tarsal segments. Identification is straightforward for many species but some Amara may be problematical and need to be dissected. Most species are fully winged or wing-dimorphic. A very valuable guide to Amara can be found HERE. UK species of Platyninae Bonelli, 1810 also have two setiferous punctures beside each eye but here the elytral epipleura are not crossed and the front tibiae are narrower and more parallel-sided towards the apex compared with those of the present subfamily.
Many species within this subfamily are phytophagous, either as adults or as both adults and larvae, more especially in the Zabrini but more generally among the Pterostichini as well, this is atypical of carabids but is also seen in many groups within e.g. Harpalinae. The UK list includes typical ground beetles but more widely the subfamily includes many highly adapted cavernicoles and hypogean species and many of these may be found in Mediterranean Europe and North Africa. Most of our UK species are widespread and common across Europe and, while we certainly have our share of rare and very local species, many are also abundant and widespread here and so the group is a rewarding one to study, more especially as many are large and distinctive and there are several very good English keys available.
Our UK species of Poecilus occur in dry and open grassland, heathland and moorland, often on lighter or sandy soils and usually among dense vegetation, they are sometimes active during the day and may be found by grubbing among tussocks etc, especially on field margins and headlands, but they are also crepuscular and nocturnal and will be seen running on pathways etc. on warm summer evenings. Stomis pumicatus (Panzer, 1796) occurs in a range of undisturbed habitats including woodland, moorland and parkland, it is generally common and adults will soon be found by general collecting both by day and night. Pterostichus occur in a variety of habitats, some are confined to the coast and several of our species occur mostly in woodlands, many will be found in wetlands or on permanently damp pasture etc. but many are generally abundant and will be found under logs and debris in a wide range of situations, they are mostly nocturnal predators both as adults and larvae and several will soon be found by searching pathways and wetland margins by night.
Species of Amara occur in a very wide range of habitats but it is probably fair to say that the majority are xerophilous, inhabiting open grassland, agricultural land and pastures, a diverse range of species occur in disturbed areas and so will be found in gardens, parks and allotments; many common species prefer certain conditions but occur generally e.g. A. aenea (DeGeer, 1774) prefers dry conditions and is often common in gardens, parkland, woodland and moorland etc. while A. plebeja (Gyllenhal, 1810) prefers moist conditions and is often abundant in all kinds of marginal situations, others are more specialist and confined to uplands or coastal areas. Adults are mostly nocturnal and will be found running on pathways or may be swept from vegetation, but they are also active in bright sun when several common species may be observed running on pavements or parkland pathways. Adults are phytophagous and often climb grass stems etc to obtain seeds, hence they are frequently swept from vegetation while larvae are ground dwelling predators, consuming eggs and larvae of other arthropods. At certain times adults may be found in great abundance e.g. locally we find A. apricaria (Paykull, 1790) by day and night on pathways and seeded umbel heads during late summer and autumn. Zabrus are generally phytophagous as both adults and larvae and in at least one case, that of the widespread and common Z. tenebroides, are sometimes pests of agricultural products. Curtonotus aulicus (Panzer, 1796) is widespread and common in open and dry habitats across the UK, A. convexiusculus (Marsham, 1802) is mostly coastal while C. alpinus (Paykull, 1790) is a very rare insect of the Scottish Highlands. All are phytophagous as adults.
Sampling is straightforward as many species are common and widespread, searching under debris or among tussocks will produce many species, pitfall trapping and sweeping are very rewarding and flight-interception and light trapping can be very productive. Adults of many species are long-lived and so may be found throughout the year although many aestivate in the soil during middle or late summer and may temporarily vanish, this does not occur every year and sometimes there is no change in the numbers of adults counted on pathways at night through the spring and summer.
PTEROSTICHINI Bonelli, 1810
ZABRINI Bonelli, 1810