Carabus nitens Linnaeus, 1758
Of the 4 Palaearctic Hemicarabus Géhin, 1876 this, the type species, is the only one to occur in western areas; it is widespread but very local and generally rare throughout central, eastern and northern Europe extending north to the Arctic Circle in Scandinavia; it has suffered a recent and sometimes severe decline in many areas due to the loss or fragmentation of heathland or a reduction in habitat quality and there have been attempts to re-introduce it to some areas of its former range in Germany and Holland. In the UK it is widespread in Northern England, Southern and Central Scotland and Northern Ireland but in the south it is very local, generally rare and mostly confined to the south of Dorset and Hampshire. It is generally a sun-loving species of open habitats and tolerant of a wide range of conditions; in much of northern Europe it is an upland and mountain species associated with peat bogs and permanently wet dwarf shrub heathland but it also occurs on dune slacks and among patchy vegetation in sandy areas whereas in the south it is mostly associated with dry Calluna heaths, damp Erica heathland or dry coastal areas. In the UK the habitats are much the same as those across Europe and, as in Europe, it seems to be in decline. Adults occur year-round but are mostly active between April and July and show very little autumn activity, they are diurnal predators and may be seen running among heather etc. in bright sun; in most of Europe it is univoltine, mating occurs in the spring and the predatory larvae develop through the summer to produce autumn adults which overwinter and mature rapidly early in the year. Development is reported to be rapid, from 35 to 40 days from egg to adult, with the pupal stage lasting 8 or 9 days. Adults in more northern populations live longer, they overwinter and reproduce for several seasons and this is thought to be responsible for their abundance in some far northern areas.
At 13-18mm this is relatively small compared with our other Carabus species but it is absolutely distinctive and might only be confused with the larger, 20-28mm, C. auratus; nitens is on average much smaller and has differently sculptured elytra. Dorsal surface entirely metallic; head, pronotum and elytral margins red to golden or coppery, elytra otherwise green with black stripes, appendages black or the legs may be weakly metallic. On the continent rare variations have the elytra metallic red, the pronotum green or the entire beetle may be dull black; the entirely black form, which has also been recorded in the UK, occurs particularly in the far north of Scandinavia. Head elongate with prominent mandibles and convex eyes, vertex sparsely punctured and wrinkled. Pronotum transverse, rounded laterally and with backwardly-produced posterior angles, surface finely punctured and, especially towards the base, rugose. Elytra with granular microsculpture between strongly-raised shiny black ridges which extend almost to the apex but may be interrupted, especially in the apical half; in C. auratus the elytra are smooth between keels that are metallic. Legs long and robust; middle and hind tibiae long and straight, anterior tibiae broadened towards the apex and lacking an internal antennae-cleaning notch, all tibiae with 2 strong apical spurs. Male pro-tarsi with dilated basal segments.