CARABINAE Latreille, 1802
This group includes some of our most impressive ground beetles. Most species are terrestrial, and some such as the violet ground beetle are among the most popular British beetles.
This large and very distinctive group includes 2 tribes, Cychrini Laporte, 1834 and Carabini Latreille, 1802. The latter is divided into 2 sub-tribes, Carabina Latreille, 1802 and Ceroglossina Vacher de Lapouge, 1927. The latter includes the single large Neotropical genus Ceroglossus Solier, 1848, members of which resemble elongate and narrow, often brilliantly metallic, species of Carabus. Carabina includes, basically and notwithstanding attempts to split them, 2 genera; Carabus and Calosoma although each includes many subgenera, some of which will be found as full genera in the literature.
Carabus Linnaeus, 1758
Carabus Linnaeus, 1758 is a very diverse genus of more than 1000 species, along with numerous subspecies, classified among almost 100 subgenera; the number of subspecies cannot yet be reliably estimated as in many cases it is unclear whether regional variations represent genuine subspecies or simply races, it is the nominate genus of the family and the one in which Linnaeus included almost all of his ground beetles. Despite being a very morphologically diverse genus, and despite some authors e.g. Jeannel, 1941-42 and Ishikawa, 1978 dividing it into several distinct genera, the group has proved to be very resistant to splitting, and this further despite its immense popularity with collectors. The genus is Holarctic with species present in Iceland, North Africa, the Canaries, most Mediterranean islands and Japan, but by far the greatest diversity is in the Palaearctic region, particularly in the east e.g. >260 are listed from China, and mountain areas may be very diverse; the Oriental region is poor in species and only 14 are recorded from North America, of which 3 are adventive, while the central European fauna includes about 30 species, 135 are recorded from Europe as a whole, and the relatively tiny state of Abkhazia (e.g.) on the Black Sea boasts 72. The UK fauna consists of 12 species in 11 subgenera and this includes the type species, C. granulatus Linnaeus, 1758. New species are regularly described, especially from China, but even the fauna of south-eastern Europe is not yet fully understood. They occur in a very wide range of habitats e.g. woodlands, grasslands or wetlands and most are flightless nocturnal predators although some subgenera are stenotopic and highly specialized e.g. the 2 species of Cathoplius Thomson, C.G., 1875 live in desert habitats along the
Violet Ground Beetle
coast of north-western Africa and both adults and larvae are diurnal, while some are cold-adapted over parts of their range e.g. C. nemoralis Muller, O.F., 1764 or C. problematicus Herbst, 1786. Many species are apterous and have fused elytra which are adaptations to a foraging terrestrial lifestyle among soil and leaf-litter etc, and where species are widely distributed, which is common among the genus, geographically isolated populations have evolved into distinct subspecies which has made the intraspecific classification and nomenclature very complicated and difficult to understand. The larvae are nocturnal predators of insects, worms and molluscs etc, when fully grown they tend to be large and heavily sclerotized and while most develop through the summer from eggs laid in the spring some develop over a number of years. They generally develop rapidly, pass through 3 instars and pupate in the soil. The genus includes some of the largest carabid species, certainly in the northern hemisphere, and while they are morphologically very diverse they are as a whole distinct and readily recognizable among ground beetles; they are elongate with separately rounded pronotum and elytra, long and filiform antennae and long and robust legs, a few have become atypically slender and elongate e.g. the Japanese snail-feeding C. (Damaster Kollar, 1836) blaptoides (Kollar, 1836). They range from about 10mm to 60mm, are rather flattened to very convex, especially the elytra, and while most are dark overall they often have distinctive metallic reflections, this is spectacularly developed in e.g. species of Chrysocarabus Thomson, C.G., 1875. The head is usually well-developed; elongate and smoothly convex with robust projecting mandibles and convex eyes. The pronotum is generally near-quadrate although there are many notable exceptions, moderately to weakly convex and variously depressed, especially towards the posterior angles, laterally explanate, bordered and rounded but usually sinuate before backwardly-projecting hind angles, posterior margin without a distinct border. Elytra variously convex usually narrowly explanate, the explanate margin often contrasting in colour with the rest, and evenly rounded from weakly-developed and usually sloping shoulders to a continuously rounded or acuminate apex. They vary from almost smooth to very strongly sculptured; the sculpture consists of various longitudinal interrupted striae, tubercles or carinae, often rows of elongate tubercles or fovea separating dense smaller striae, in some Coptolabrus Solier, 1848 these tubercles are raised and shiny, reminiscent of Elaphrus, in Tachypus Weber, 1801 with strongly raised carinae but otherwise simple. The elytral sculpture is hugely variable across the genus but also within species, more so than in any other carabid genus, and has given rise to a bewildering list of subspecies, races and varieties. The legs are long and robust with well-developed tarsi and claws, the tibiae have two long apical spurs and the pro-tibiae lack an antenna-cleaning notch on the inner margin.
Calosoma Weber, 1801
Calosoma Weber, 1801 includes between 128 and about 170 species, depending on whether some geographical races are considered distinct, in 17 subgenera and is cosmopolitan; in the northern hemisphere, unlike Carabus, it is more diverse in the Nearctic region, with 90 species, than the Palaearctic, with about 75. Several subgenera e.g. Calopachys Haury, 1880 or Callisthenes Fischer von Waldheim, 1820 will be found listed as distinct genera which may be further divided into sub-genera, but the group is, especially in tropical areas, and more-especially given the history of its classification and nomenclature, only poorly understood and these aspects need to be worked out. The biology is essentially different to that of Carabus; adults of most species are fully-winged and many are strong fliers e.g. the European C. sycophanta (Linnaeus, 1758) is regularly recorded in the UK, and the North African C. olivieri Bedel, 1895 regularly crosses the Mediterranean into Europe, thus the much smaller diversity when compared to Carabus becomes understandable. Adults may be diurnal, nocturnal or both, and some occasionally appear in light-traps in very large numbers; many are predators of lepidopteran larvae, either on the ground or among foliage on trees and shrubs, fertility increases as prey populations increase and so large outbreaks of larvae tend to be accompanied by similar increases in beetle numbers. The Palaearctic species C. sycophanta (Linnaeus, 1758) has been introduced into North America as a biocontrol agent of the Gypsy Moth, Lymantria dispar. Some exotic species are short-winged and adapted for a terrestrial lifestyle, similar to that of Carabus, these are widespread and include species of the Palaearctic subgenus Callisthenus from Central Asia, the Nearctic Callistenia Lapouge, 1929 and the Central American Carabomimus Kolbe, 1895. Most of the more typical species occur in wooded or meadow habitats worldwide from lowland to high mountain altitudes e.g. C. maderae ssp. indicum Hope, 1831 occurs in meadows up to 4000m in the Himalayas, it is short-winged but otherwise typical of the genus. Other more specialized groups occur around the African Rift Valley up to 4000m and in high Andean deserts up to 3500m. Three species occur in the Galapagos Islands; they are among the smallest of the genus and have reduced wings but are otherwise typical.
Typically these are very distinct beetles and only likely to be confused with various Carabus but distinguished by the very short second antennomere, wrinkled mandibles and regularly striate elytra. They are large and flattened with the head narrower than the pronotum and the pronotum narrower than the elytra, the colour is very variable; many species are dark and drab but there are also brilliant metallic species which tend to vary widely in colour. The head is smoothly convex or variously wrinkled around the very convex eyes, with large robust mandibles and long filiform antennae. Pronotum widely transverse, rounded laterally and usually sinuate before backwardly projecting posterior angles, variously explanate and usually strongly bordered laterally and wrinkled or punctured dorsally but usually without well-delimited fovea. The elytra are broad with distinct shoulders and often widest behind the middle, typically with numerous punctured striae and often with series of larger punctures along various striae or interstices. Two species occur in the UK; C. sycophanta (Linnaeus, 1758) is a fairly regular vagrant from the continent which has not become established, its occurrence probably coincides with population explosions on the continent which are associated with outbreaks of various lepidopteran larvae, and the native C. inquisitor (Linnaeus, 1758) which is a very local woodland species. Both are arboreal predators of lepidopteran larvae, C. sycophanta is mostly diurnal while C. inquisitor is generally nocturnal.
A key to the UK species of Carabinae can be found HERE.