HARPALINAE Bonelli, 1810
This large group of ground beetles will sometimes be found to include the majority of the western Palaearctic species in a series of tribes e.g. Pterostichini Bonelli, 1810 and Zabrini Bonelli, 1810 among many others, and the latest UK checklist treats our fauna accordingly but the classification will be found to vary widely and some of these tribes are variously given as distinct subfamilies. In the widest sense the subfamily is sometimes divided into two supertribes: Pterostichitae and Harpalitae, with the Harpalini further divided into a series of subtribes, some of which are represented in the UK. Here we define the subfamily in a very narrow sense, mostly because it is thus very straightforward to define; briefly as those species with rounded elytral apices, antennae pubescent from the third segment and the head with a single setiferous puncture beside each eye, this combination of characters is also seen in the otherwise very different Callistus lunatus (Fabricius, 1775) but nonetheless it makes the UK genera easy to identify. There have been many changes to the nomenclature and classification over the years, especially among the larger genera, and it will be absolutely essential to refer to the latest checklist when working with this group. On the other hand there are several excellent modern identification works which make the task much easier. The following tribes, or subtribes as the case may be, are represented in the UK.
Anisodactylini Lacordaire, 1854 includes about 350 species in 31 genera; it has a worldwide distribution and is well-represented across the Holarctic region with about 50 species of six genera occurring in the Nearctic region and 16 species of six genera occurring in Europe. Five species of the following three genera occur in the UK. Anisodactylus Dejean, 1829 is a Holarctic group which extends south into North Africa and the Near East; it includes 50 species in nine subgenera and is most diverse in North America; nine species of five subgenera occur in Europe, of which three species of two subgenera extend to the UK. The very widespread European species, Diachromus germanus (Linnaeus, 1758), the only member of the genus, occurs very occasionally in the UK, usually near to the south coast and probably as a vagrant. Scybalicus Schaum, 1862 includes four species of which two are European; S. minoricensis Vives & Vives, 1994 is endemic to the Balearic Islands while the widespread S. oblongiusculus (Dejean,
1829) occurs sporadically in the south of England. Our UK species are easily identified: Diachromus is medium sized, 7.5-10.0mm, with pubescent elytra and characteristically coloured; reddish brown with the pronotum and an apical elytral macula dark metallic blue or green. Scybalicus is relatively large at 11-13mm, the body is pale to dark brown and punctured and pubescent throughout and, distinctive for this species, the basal elytral margin is sinuate in front of the third and fourth interstices. Species of Anisodactylus are superficially similar to those of Harpalus Latreille, 1802 but here the first segment of the posterior tarsi is longer and much longer than the apical spur, giving rise to the vernacular name of ‘short spur beetles’.
Harpalini Bonelli, 1810 is a cosmopolitan and very large group of more than 70 genera, the western Palaearctic region is speciose though relatively poor in genera; the group is represented in the UK by only two genera. Harpalus is a large genus of more than four hundred species in seven subgenera although some of these e.g. Pseudoophonus Motschulsky, 1844 are variously regarded as distinct genera, it occurs throughout the Holarctic region, extending south into tropical Africa and the Oriental region but the greatest diversity is in Asia; about sixty species occur in North America and more than one hundred in Europe of which twenty extend to the UK. Ophonus Dejean, 1821 is a large genus of about seventy species which are all native to the Palaearctic region although two of the most widespread and generally common species; O. puncticeps Stephens, 1828 and O. rufibarbis (Fabricius, 1792) have become established and are widespread in the USA. Both were first recorded in the 1950’s. More than 40 species occur in Europe of which thirteen occur in the UK. A further fifteen genera representing more than sixty species occur in Europe. Our UK species are medium sized beetles, 5.2-16.0mm, of a fairly uniform elongate-oval or parallel-sided habitus, the head lacks frontal furrows and the antennae are at most only moderately long. The pronotum and elytra overlap, the pronotum is transverse to quadrate, with or without distinct posterior angles and in most there are only shallow and indistinct basal fovea. The elytra have nine complete striae and an abbreviated scutellary striole, the interstices have various dorsal setiferous punctures and the outer interstices may have a group, or several groups, of preapical punctures. The legs are robust and in many rather short, the basal metatarsomere is short (when compared with Anisodactylus), much shorter than the following two combined, and characteristically about as long as the apical tibial spur. Ophonus differs from Harpalus in having the head extensively punctured and pubescent.
Stenolophini Kirby, 1837 is a large and cosmopolitan group of about thirty genera which is only poorly represented in Europe by about eighty species of seven genera, of these twenty three species of five genera occur in the UK. The majority are small, between 2 and 5mm, and drab insects, most (Dicheirotrichus are an exception) lack a sensory seta at the posterior pronotal angles and (in UK species) the pronotum lacks the raised basal bead seen in most members of the Harpalini. More fundamentally the tribe is distinguished from other groups within the subfamily by having two (or there may occasionally be an extra one on one or both sides) sensory setae on the penultimate labial palpomere, in other tribes there are at least three setae. The genera are quite distinctive but specific identification can be very difficult without reference material, especially with species of Bradycellus Erichson, 1837 and Acupalpus Latreille, 1829. The position of Trichocellus Ganglbauer, 1892 remains uncertain; it is variously treated as a distinct genus or as a subgenus of Dicheirotrichus Jacquelin du Val, 1857, two species of each group occur in the UK and both may be recognised by the rudimentary or missing scutellary striole and pubescent elytra; in the former group this is confined to the outer elytral intervals whereas in the latter the elytra are pubescent throughout. In our remaining genera the elytra are glabrous. Species of Bradycellus are distinct in having a central tooth on the mentum (chin) but in any case our UK species have pale antennae which will distinguish them from the remaining three genera. Our three species of Stenolophus Dejean, 1821 are relatively large at 5-6.5mm and distinctively coloured; the pale-margined dark pronotum of the very common S. mixtus (Herbst, 1784) will soon become familiar when examining wetland carabids. Members of the remaining two genera are small, <5mm and readily distinguished; Anthracus Motschulsky, 1850, formerly included in the following genus, includes a single UK species, A. consputus (Duftschmidt, 1812) which is distinguished by the cordiform pronotum with sinuate lateral margins and sharp posterior angles. Our eight species of Acupalpus Latreille, 1829 are small, at most 4.5mm but usually 2.5-4.0mm, and rather nondescript beetles recognized within the group by the dark antennae and rounded pronotal angles. The European fauna includes only a further three genera and so our list is quite representative but on a wider scale the genera are widespread and fairly speciose: Acupalpus (>100 spp.) with 25 in Europe, Stenolophus (about 70 spp.) with 11 in Europe, Bradycellus (>100 spp.) with 17 in Europe, Dicheirotrichus (including Trichocellus) (>40 spp.) with 17 in Europe, and Anthracus (30 spp.) with 7 from Europe.
Two further groups occur in Europe but not in the UK which are generally considered as subtribes of the Harpalini. Amblystomina Fauvel, 1889 is represented by nine species of Amblystomus Erichson, 1837 whereas the Ditomina Bonelli, 1810, a large group of twenty six genera, is represented by thirty nine species of eleven genera, some of which e.g. Dixus (above) are quite atypical of the subfamily.
Ecologically the UK species are quite diverse and will generally occur in specific habitats. Species of Stenolophus, Acupalpus and Anthracus occur in wetlands generally although, as always, there are exceptions; Acupalpus parvulus (Sturm, 1825) and A. meridianus (Linnaeus, 1760) occur more generally and A. exiguus Dejean, 1829 also occurs in salt marshes. Bradycellus species inhabit drier habitats such as heaths and moorland but some are synanthropic and may be attracted to light in numbers in domestic gardens. Dicheirotrichus are a varied group, our two species of Dicheirotrichus s.str. are restricted to saline coastal habitats while our two members of the subgenus Trichocellus occur inland as well; T. cognatus on dry heaths and heather moors, and T. placidus in wetlands generally as well as permanently damp grassland and woodland. Diachromus germanus (Linnaeus, 1758) is a mostly southern European species which is generally rare in northern areas and only very occasionally occurs in dry habitats near the south coast of England. Scybalicus oblongiusculus (Dejean, 1829) occurs very rarely in open dry habitats near the south coast but adults are nocturnal and it may be under recorded, it is worth looking for at night as we found a specimen in a local Watford park. Anisodactylus binotatus (Fabricius, 1787), one of our largest species, is generally common on damp arable land and grassland but may also occur in gardens and other disturbed areas, A. poeciloides (Stephens, 1828) is a very local and generally rare coastal species of south and east England which often occurs in among salt marsh vegetation, and A. nemorivagus (Duftschmid, 1812) is a rare dry-heathland species of southern England and Wales. Species of Ophonus inhabit dry areas, often exposed to the sun and often with patchy vegetation; calcareous grassland and sandy heaths are good places to find them, many may be found on agricultural headlands or coastal dunes and they are generally active at night, remaining beneath debris or among matted grass or tussocks during the day. Some of our species are rare or very rare but many are widespread, albeit local, and may be found by pitfall trapping or nocturnal searching, and in general the most diverse areas are around the coast of southern England and Wales. Much the same applies to species of Harpalus although they are generally more common and diverse, at least across the south, and several species should quickly be found to be common; H. affinis and H. rufipes are among the most common of our medium-sized carabids. All members of the subfamily are terrestrial and most are nocturnal although wetland species tend to be active by day and night, most are thought to be predatory but the larger species are well-known as being omnivorous and will often occur by sweeping as they climb stems to feed on seeds.
Identification can be a challenge; assigning specimens to genera is straightforward for the UK fauna but members of e.g. Harpalus, Ophonus, and Bradycellus will need to be examined very carefully and in some cases dissected. Fortunately there are several very good guides to our species and a wealth of information as well as a few keys on line; a very good way to become acquainted is to read the RES Handbook (1974) by Carl Lindroff which is available free to download, the more recent (2007) Handbook by Martin Luff is the benchmark work for our fauna but the guide by Trevor Forsythe and the first volume of Andrew Duff’s Beetles of Britain and Ireland are also very good.