Curtonotus Stephens, 1827
Formerly included within Amara Bonelli, 1810, this Holarctic genus includes almost one hundred species, with the greatest diversity in mountain regions of Asia while only twelve species are known from Europe. Of the fifteen or so Nearctic species, five are Holarctic and one, (C. aulicus (Panzer, 1796) ) is an established and widespread introduction from Europe. All the European species are widespread across the Palaearctic region but of these only three are widespread in Europe, the others displaying the essentially Asian origins of the genus. Some have very restricted distributions e.g. C. alexandriensis Heike, 1988 is known only from Kyrgyzstan and C. baimaxueshanica Heike, 2010 has recently been named from China, but many are widespread and these include the majority of the European fauna. The following European species occur across much of the Palaearctic region but are restricted to certain parts of south-eastern Europe, mostly Ukraine and south-western Russia: C. brevicollis (Chaudoir, 1850), C. castanea (Putzeys, 1866), C. cribricollis (Chaudoir, 1846), C. deserta (Krynicky, 1832) and C. propinqua Ménétriés, 1832, while C. fodinae Mannerheim, 1825 and C. torrida (Panzer, 1796) are also widespread across the Palaearctic region but extend only into parts of north-eastern Europe. The cold-adapted C. alpina (Paykull, 1790) is circumpolar, occurring only at high latitudes in northern Europe, including the UK, while another cold-adapted species, C. gebleri Dejean, 1831, is more widespread, extending into the central and northern European mountain ranges and occasionally occurring elsewhere but it has not been recorded from the UK. Our other UK species, C. aulicus (Panzer, 1796) and C. convexiusculus (Marsham, 1802), have very widespread Palaearctic distributions. In general the genus occurs from Arctic and tundra regions south to cooler temperate areas, most species occur in open and rather dry places on heavy or calcareous soils and of the widespread species some are common in coastal areas, although none are exclusively maritime, and some are associated with mountain valleys or riparian flood plains. Most species are univoltine and nocturnally active and adults of the few species that have been studied are known to feed on seeds, mostly at night when they may climb stems to do so. Most are fully-winged; they fly in the evening or at night and many have occurred at light traps. Larvae display varied phenology, developing through the summer or winter, first and second instars develop rapidly but third instars often diapause before pupation to produce adults in late summer, coinciding with the abundance of mature grass seeds etc. Larvae tend to be polyphagous although most are thought to be primarily seed-feeders; those of C. aulicus need seeds in order to develop successfully while those of C. convexiusculus have been reared on seeds, mealworm larvae or a mixture of both. This flexibility may allow closely related species to share the same habitats.
Most species are large, >10 mm, dark in colour and robust with elongate bodies, a relatively large head and cordate pronotum, in general appearance superficially resembling Pterostichus but distinct in having at least three setae on the penultimate labial palpomere. The following combination of characters will identify the genus among our UK fauna: mandibles sharp and symmetrical, the outer margin without a setiferous puncture, dorsal surface glabrous, head with two setiferous punctures beside each eye, maxillary palpi normally developed, pronotum with well-developed basal fovea, elytral with rounded apices and crossed epipleura, striae punctured and impressed, interstices without setiferous punctures, apex of front tibiae strongly widened. Larger than most species of Amara but distinct from that genus in that the prosternal process is not bordered. They soon become obvious in the field due to their large size and general appearance. Our UK species are readily distinguished as follows:
Smaller species, at most 11 mm. Antennae extensively dark, pale only at the base.
Larger species, mostly >11 mm. Antennae entirely pale brown.
Pronotum more strongly sinuate towards the base, the posterior angles strongly protruding. Raised lateral border of pronotum not extending to the posterior angles.
Pronotum less strongly sinuate towards the base, the posterior angles hardly protruding. Raised lateral border
of pronotum reaching the posterior angle.
Curtonotus alpinus (Paykull, 1790)
This species has a Holarctic distribution, occurring across far northern parts of the Palaearctic region from Fennoscandia to the far east of Russia, it is present on the Aleutian Islands and there are recent fossil remains from Greenland. In North America it is more widespread and extends much further south; along the Rocky Mountains as far as California, but is generally absent further east, it is widespread and locally common across much of Northern Canada and Alaska and is the most northerly of the Nearctic carabids. In Europe it is very local and generally rare, being restricted to northern and central parts of Fennoscandia where it occurs beyond 1650m, higher than any other beetle, and there are a few relict populations in the Scottish Highlands. Typical habitats in Europe are moraines and open grassland with patchy grass or dwarf shrub- open woodland cover, usually on poor or sandy soils, while across northern Russia it is more characteristic of the tundra. In North America, where it is usually quoted as an autumn breeder, it is typical of dry sandy soils in upland and mountain regions but also occurs on ruderal sites further south. In northern Europe the adults are active from June until October, they peak in abundance during July and it is likely only a certain percentage will overwinter as numbers of dead adults are present from August. The life history is not well known but mating has been observed in July and immature adults are present in August. The duration of larval development is uncertain, they may complete their development during the summer or, which is more likely, overwinter and finish developing during the following spring and summer. Both adults and larvae are thought to be primarily seed-feeders although cannibalism has been observed in larvae. In Europe adults are fully-winged and have well-developed flight muscles but flight has not been directly observed, while in the UK the species is usually reported as apterous. The species is primarily nocturnal although swarming in bright sun has been observed; adults spend much of their time under stones or matted vegetation but ascend grass and dwarf shrubs, mostly at night, to feed.
9.0-11.0 mm. Body entirely non-metallic black, sometimes with the elytra reddish-brown, legs black or with femora and tarsi partly reddish, antennae gradually darkened from pale basal segments. Head with two setiferous punctures beside each eye, maxillary palps long and slender, and antennae densely pubescent from the fourth segment. Pronotum transverse, broadest slightly in front of the middle and sinuate just before very weakly projecting posterior angles, lateral borders narrow, complete to the base but not merging with the basal keel, surface punctured across the base except medially and with doubled fovea, the external fovea delimited by a fine ridge which reaches the basal border. Prosternal process not bordered. Elytra elongate (about 1.6X longer than wide) and more-or-less parallel-sided from rounded shoulders to a weak subapical constriction, striae narrow and finely punctured, interstices flat, the third without setiferous punctures. Males may be distinguished by the dilated front tarsi and modified middle tibiae.
Curtonotus aulicus (Panzer, 1796)
This species is widespread and generally common throughout Europe from Spain and central Italy in the south to the UK and far above the Arctic Circle to the north; it extends through Asia Minor and Russia into Siberia and has become established in eastern Canada and the United States following accidental introductions with ship ballast. It is generally common and often abundant throughout the UK including all the islands north to Shetland and widespread though sporadic and local across Southern Ireland. Adults occur year-round although they are mostly recorded from July until October and tend to remain hidden for the rest of the year; typical habitats are well-vegetated river and agricultural margins although they will occur in most not too wet habitats and are often common on disturbed sites such as parkland and domestic gardens. Adults are both diurnal and nocturnal and spend much of their time climbing among herbaceous vegetation; they are primarily vegetarian and will be found among the flowers of various Asteraceae and Apiaceae where they consume seeds. Breeding occurs in late summer and autumn, although it is not known whether the current year adults reproduce or whether they need to overwinter before reproducing during the following summer and autumn. Larvae are also vegetarian and need to consume seeds for successful development although they are very likely to consume a range of organic matter including, occasionally, eggs and larvae of other insects, first instars develop late in the year and it is generally second instars that overwinter and continue developing in the spring, final instars diapause before pupating in the summer to produce adults from June onwards. Adults are occasionally seen from early summer but they increase in numbers from August and by September are usually abundant, during the day they generally remain hidden among tussocks or under debris but may often be seen on umbels, thistles and burdock that have formed seeds and at this time mating pairs are common, at night they may be seen on flowers in numbers or on pathways etc. and they sometimes come to light.
Adults are large, broad and discontinuous in outline and this form will soon become absolutely distinctive in the field. 10.5-15.0 mm. Body reddish-brown to very dark brown, often with a metallic brassy reflection, appendages paler reddish-brown. Head large, broad and rather flat, with two setiferous punctured beside convex and protruding eyes, frontal furrows obsolete or weakly developed, mandibles broad and blunt and antennae thin and relatively short. Pronotum widely transverse, rounded laterally and strongly sinuate before acute and protruding posterior angles, lateral border not reaching the posterior angle, basal third extensively punctured and with doubled fovea, the outer delimited externally by a keel that merges with the lateral border at its base. Elytra broader across the base than the base of the pronotum, widest behind the middle and continuously curved around the apical margin, with impressed and finely punctured striae, including a scutellary striole, and convex interstices which lack dorsal punctures, epipleura crossed before the apex. Legs long and robust, front tibiae with an antenna-cleaning notch and all tibiae with sharp apical spurs that are shorter than the first tarsal segment. Male middle tibiae broadened and with a strong median tooth and sub-apical tubercles.
Curtonotus convexiusculus (Marsham, 1802)
Still widely referred to as Amara convexiusculus; Curtonotus being included as a subgenus of Amara Bonelli, 1810. Widespread across Europe but with a discontinuous distribution in the south, this species occurs from France to Greece and north to the UK and reaching above the Arctic Circle in Scandinavia although it is missing from various regions e.g. Switzerland. To the east it extends through Asia Minor and Russia to the Caspian Sea and southern parts of Siberia, it is often quoted as reaching the eastern Palaearctic region but this may be in error. In the UK it is generally common along the southern and eastern coasts of England, including much of the Thames and Humber catchments, extending north to southern Scotland, and locally common across southeast and central England. In the west it is much more local and rare, there are coastal records from Anglesey, the Western Isles and Ireland but, with the exception of the south coast of Wales, it seems to avoid the Atlantic climate. The species is often associated with saline or maritime habitats, certainly in Northern Europe, and this has sometimes lead to the opinion that it is halophilic, indeed it was formerly considered to occur as two subspecies with ssp. bohemicus (Fassati, 1944) occurring inland the nominate subspecies coastal, but it occurs inland throughout Europe and is not necessarily associated with salt. Typical habitats are vegetated coastal shingle banks, dunes and grassland, often with patchy herbaceous vegetation, more generally the species does not display any preference for soil type or habitat; it occurs on permanently damp heavy clay soils, peaty or loamy substrates and calcareous grassland, usually in partly shaded or open situations but also, occasionally, in open woodland and often on ruderal sites. Adults occur year-round; they are active from early spring until late in the autumn and peak in abundance from June until September, they are mainly nocturnal, spending the day under debris or matted vegetation, including stranded seaweed, but they may be active during hot summer spells when specimens will occasionally bask on low foliage. Reproduction occurs during spring and early summer and females oviposit in the ground from late June until late august or September. Both adults and larvae feed primarily on seeds, and while the long-lived adults may overwinter this is done mostly by the larvae. Eggs hatch in the autumn and larvae develop through the winter and early spring within small cells in the ground, they stock them with seeds so that they can continue feeding through the winter and become active in early spring. Pupation occurs within the larval cell from April or May and adults emerge from June although in warmer years they may remain underground, aestivating through the warmest parts of summer. Adults should be looked for at night when they often climb plant stems to feed or run on turf or pathways etc., and they sometimes occur on vegetation beside water although they are not riparian. Pitfall traps may also produce adults and sometimes in numbers as they occasionally swarm, adults are fully winged, they are good fliers and have been widely reported from light traps.
11.0-13.0 mm. Body dark brown, usually faintly metallic, legs and antennae reddish-brown. Head with two setiferous punctures inside convex and protruding eyes, the surface smooth and only very finely punctured. Maxillary palps long and slender; the penultimate segment with at least three setae along the inner margin. Antennae slender with all segments elongate, densely pubescent from the third segment. Pronotum transverse, widest slightly in front of the middle and gently sinuate before acute posterior angles that hardly project laterally, raised lateral border complete to the basal margin, surface weakly convex and usually with fine transverse wrinkles, strongly punctured only towards the base, basal fovea doubled, the external fovea with a fine ridge that reaches the basal margin. Prosternal process not margined. Elytra elongate, about 1.7X longer than together wide, and only slightly widened from rounded shoulders to a weak subapical constriction, striae, including a long scutellary striole, weakly punctured and interstices distinctly convex, the third without setiferous punctures. Legs long and robust, the front tibiae rather strongly broadened apically and the hind tibial spurs much shorter than the basal tarsomere. Tarsi 5-segmented with smooth claws. Basal segments of front tarsi dilated and middle tibiae with a strong median internal tooth in males.