Ocys Stephens, 1828
This is a small western Palaearctic genus of about 25 species and subspecies, the majority are very local and rare and restricted to small areas, mostly in mountain regions of North Africa, Spain and Italy but a few are endemic to Mediterranean islands e.g. O. beatricis Magrini, Cecchi & Lo Cascio, 2000 from Sicily. All are small to medium sized and of typical carabid appearance; elongate to broadly-oval and brown to black with pale appendages. Among out UK fauna they are very similar to Bembidion, with the same diminutive terminal maxillary palpomere, but distinguished by the apically recurved sutural stria which ends in a raised keel above the apex of the eighth stria, and any setiferous punctures being situated in the apical half. Three species are widespread and all extend north into the UK, of these one has only recently been recognized (see below), and one, O. quinquestriatus (Schaum, 1857) is also represented in Europe by the endemic Greek subspecies subtilis (Schaum, 1857).
Black to dark reddish-brown with a distinct metallic blue lustre. Pronotal basal margin curved forwards towards obtuse posterior angles. 3.9-4.7mm
Colour variable, entirely pale to dark brown or with forebody and elytra contrasting, with at most a faint metallic reflection. Basal margin of pronotum straight towards sharp posterior angles. 4.2-5.8mm.
Ocys harpaloides 1
Ocys tachysoides 1
Ocys quinquestriatus 1
Ocys harpaloides 2
Ocys tachysoides 2
Ocys harpaloides 3
Elytra paler, reddish brown and usually paler on the disc than along the lateral and apical margins. Elytral microsculpture consisting of narrow and less closely spaced transverse lines that tend form long cells. Ventral margin of the aedeagus (lateral view) more strongly curved down towards the apex, dorsal margin more strongly arched towards before a subapical constriction. Spermatheca broadly and evenly rounded above and strongly constricted below, overall appearance rounded (lateral view).
Elytra mostly dark brown, almost black, sometimes narrowly paler along the suture and lateral margins. Transverse elytral microsculpture slightly wider and tending to form denser meshes. Ventral margin of the aedeagus less curved towards the apex, dorsal margin less strongly arched and either smoothly curved or only slightly constricted subapically. Spermatheca narrower, more weakly and unevenly curved above and below, overall appearance broadly elongate (lateral view).
Ocys quinquestriatus (Gyllenhal, 1810)
This western Palaearctic species occurs locally throughout southern Europe from Spain to Greece and sporadically further east into Ukraine and south-western parts of Russia, to the north it extends into Fennoscandia, where it is very local and scarce, and the UK although it is absent from some of the eastern Baltic countries. Here it is a local and mostly lowland species throughout the mainland to the far north of Scotland although it is absent from the islands (there are old records from the Isle of Man but it is now thought to extinct there), and it is widespread but very rare and mostly coastal in Ireland. Adults are present year-round but are recorded mostly from April to September, they occur under bark and on tree trunks in open woodland and wooded parkland, especially where these are densely covered with ivy, and they have been found in dry rocky coastal habitats, but they are also synanthropic and many records are from ivy-clad walls, stables or cellars where they may be associated with rodents. On the continent it is recorded from a wider range of habitats although it also seems to be synanthropic throughout its range, in south and central Europe it occurs to low mountain altitudes, is most often found in sandy or calcareous districts and often along the banks of streams and rivers where adults are sometimes found early in the year aggregated under debris or in deep cracks in the soil. This species is probably not uncommon in the UK but it is certainly seldom found, adults are active through the winter when the temperature exceeds 5°C but they are nocturnal and even then tend to remain concealed. Through the milder months they may be active on the surface at night but are cryptic and difficult to find-as we know from experience when we found a single example on the trunk of a small Prunus avium at night in our local park. Adults peak in abundance around July and are active until the first cold weather arrives, thus the species is thought to breed during winter and early spring, with larvae developing through to early summer and producing new generation adults from July. The species is macropterous and has been observed in flight in central Europe.
3.5-5.0mm. Body glabrous and dark brown, often with a metallic blue or green reflection, and pale brown appendages. Head with converging temples and convex eyes, vertex and frons smooth, frontal furrows single, short and only weakly impressed, each eye with two adjacent supra-orbital punctures. Penultimate maxillary palpomere darker than the others and much broader and longer than the diminutive apical segment (hence the genus was formerly included as a subgenus of Bembidion), all antennomeres long and slender. Pronotum transverse, broadest about the middle and curved laterally to rounded anterior angles and obtuse posterior angles, the margin slightly sinuate before the base, basal margin widely but weakly produced across the middle, surface smoothly convex; depressed inside the posterior angles but without distinct fovea. Elytra with six striae consisting of weakly-depressed rows of punctures and two outer striae that are usually much weaker, these extend into the apical third but fade before the apex; the sutural stria becomes weakly keeled and recurves around the apical margin and towards the disc, third striae with two setiferous punctures in the apical half. Legs long and slender, front tibiae with a deep antennal-cleaning notch internally towards the apex which is truncate, entire and without an apical notch.
The form of the elytra (punctured striae-including a short scutellary striole-recurved first stria and two setiferous punctures in the apical half) and front tibiae will distinguish Ocys among the Bembidiini, they superficially resemble some small Trechini but lack impressions on the head and have diminutive apical maxillary palpomeres.
Ocys harpaloides (Audinet-Serville, 1821)
Ocys harpaloides is widespread though local and of rather sporadic occurrence throughout Europe from Portugal to Greece and north to the UK and the extreme southern coast of Norway, it is also known from the Azores, Algeria, Morocco and most of the Mediterranean islands, but Bulgaria and Poland may well be the eastern limit of the distribution. Here it is generally common throughout England and Wales, including the islands, and rather less so through Scotland to the Hebrides and Orkney, in Ireland it is common across the north but more local and often coastal in the south. On the continent the species is usually associated with lowland forest areas, usually on permanently damp and heavy soils or floodplains etc. and rarely in open situations e.g. in Switzerland it occurs in lower parts of large river valleys but only up to about 600m, and in Belgium it is mainly associated with wooded river margins. In the UK it occurs more generally; among decaying wood and under bark or fallen timber in wooded areas, but also under debris and matted vegetation under hedgerows or in open situations. In general the species seems to prefer damp habitats on heavy soils but adults may occur in most situations, including disturbed areas such as wooded parkland and domestic gardens, and specimens have been found in an avian nest and among plant litter in mammal burrows. Adults occur year-round, they are active over a long season from late winter until the autumn, peaking in abundance from March until June. They overwinter under among debris under bark or in litter among fallen timber but specimens may often be found active at this time, even during the coldest spells. Breeding occurs in the spring but little is known of the biology, adults are crepuscular and nocturnal and they are fully winged (at least in the UK; specimens with reduced wings occur in northern Europe) although flight has not been observed directly. During the spring of 2005 we found them in numbers (about 20) on a single occasion at UV light in our local Watford woodland but flight was not observed. Adults are easily found by searching trunks or fallen timber at night when they are active on the surface, by day they remain under loose bark or among debris under logs etc., usually in small numbers and often alone.
4.0-6.0 mm. Very distinctive among our fauna (but see below), broadly rounded and rather convex, colour varies; entirely pale brown or with the forebody and/or elytra darker, commonly with the forebody brown and the elytra darker brown with the suture and margins paler usually with the head darker and the elytra extensively dark brown to black, often with a bluish or faintly metallic overtone, appendages entirely pale brown.. Head with large convex eyes and short temples converging to a broad neck, surface smooth but for indistinct transverse wrinkles between the eyes and weakly-defined frontal furrows. Two setiferous punctures beside each eye. Terminal maxillary palpomere diminutive (the species was formerly included in Bembidion). Pronotum transverse, broadest in front of the middle, curved to produced anterior angles and sinuate before sharp posterior angles, basal margin produced medially. Lateral pronotal margins widely explanate, surface evenly convex but for broad and ill-defined basal fovea. Elytra evenly curved from rounded shoulders to a continuous apical margin, each with five striae that extend into the apical third, sutural stria recurved at apically; the recurved part with a distinct external ridge, interstices broad and flat, the third with a single puncture which joins the third stria behind the middle. Legs long and slender, front tibiae with an antenna-cleaning notch before the apex. Tarsi 5-segmented and simple, Males may be determined by the enlarged (compared with females) basal segment of the front tarsi.
Ocys tachysoides (Antoine, 1933)
Ocys harpaloides was among the most distinctive of our small carabids until the recent discovery of O. tachysoides in the UK. O. tachysoides has been known from lowland regions of Morocco since its discovery, it was recognized from a mountain region of Portugal in 1998 and from Spain in 2013, and since then has been found to occur widely across Europe; Belgium, Ireland, Germany, UK, France, Germany and southern Norway, and there is a record from the north of Norway, about the Arctic Circle. That the species are sympatric and superficially very similar in appearance, and that both occur together in populations in southern Spain and Morocco, It seems very likely that a more extensive range will emerge for tachysoides as further specimens are identified. In the UK it has been recorded widely across the English midlands and there are records from southern Scotland and Northern Ireland. Most records are from damp broadleaf woodland but on the continent the species occurs more widely e.g. in Belgium it is recorded from freshwater marshes. Adults occur year-round, peaking in May and again in the autumn, and so the biology (which is largely unknown) is likely to be similar to that of harpaloides.
Formerly considered as a variety of O. harpaloides, the specific identity of tachysoides is now beyond doubt following genetic analysis (Maddison & Anderson, 2016). Maybe surprisingly, typical forms of the two species are rather obviously different and the identity of specimens in the wild might be suggested from their overall appearance, but atypically coloured specimens do occur and so likely specimens of either species will need to be taken for careful examination. The differences are summarized in the above key, adapted from HERE.