Carabidae | UK | Ukbeetles

CARABIDAE Latreille, 1802

Ground Beetles

A large, diverse family found in a wide range of habitats, ground beetles are one of the most popular groups of beetles, and are among the most frequently encountered.

Suborder: ADEPHAGA

Family: HYGROBIIDAE

Genus: Hygrobia

Species: H. hermanni (Fabricius, 1775)

Size: 8-10mm

ADEPHAGA Clairville, 1806

360

1.5-35mm

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Because this is an enormous family the following description is intentionally brief, firstly because we intend to add a more detailed description under the headings of the various tribes and genera, and secondly because we intend to feature a few species from outside the U.K. in order to give a wider appreciation of the group. To have attempted a description of the group on a world, or even a Palaearctic, basis would have been very ambitious indeed.

Carabids in Europe

Estimates of the number of species vary but it is safe to say that at least 40000 have been described worldwide and of these almost 3000 occur in Europe and around 350 in the U.K. Our comparatively impoverished fauna will serve to give a general idea of the Palaearctic members of the family but further south, in tropical regions, things become very much more exotic e.g. tropical Cicindelinae will be recognized as belonging to the group but it is probably fair to say that they need to be seen to be believed! European species range from 1.5 to 40mm and for the most part will be recognized from a study of our own fauna. They are characterized by the filiform antennae, the possession of sensory bristles at fixed points on the body, 5-segmented tarsi which generally consist of simple segments, prosternum with distinct notopleural sutures, basal segments of the abdomen coalescent, hind coxae large; completely dividing the first visible sternites and not expanded laterally to meet the elytral epipleurs and hind trochanters extending at least some way along the hind margin of the femora. Most carabids will quickly become obvious and, bearing in mind the above list of characters, the less obvious types e.g. Omophron Latreille, 1802 or the Scaritini Bonelli, 1810 should soon be identified as carabids. Species of some other families superficially resemble carabids but experience will soon rule them out. For example:

Some Omaliinae (Staphylinidae) with long elytra, but this group possess ocelli on the frons, a character never seen in the carabids.
Some Tenebrionidae and Anthicidae which, as with all the Heteromeran groups, have 4-segmented hind tarsi.
Some Cerambycids and Chrysomelids, all of which have the fourth tarsal segment tiny and generally enclosed by the widely bilobed third.

Ecology

Most carabids live on the ground although species of Harpalus Latreille, 1802, Ophonus Dejean, 1821, Zabrus Clairville, 1806 and Amara Bonelli, 1810 commonly climb plant stems in search of seeds, while species of Calosoma Weber, 1801 and a few Lebiini Bonelli, 1810 are arboreal. Most are predatory or for the most part predatory and some are specialized in this role e.g. species of Leistus Frölich, 1799 and Loricera Latreille, 1802 prey on springtails, and Cychrus Fabricius feed on snails. Some species of Dyschirius Bonelli, 1810 feed exclusively on staphylinids of the genus Bledius. Most species are long lived and may be searched for throughout the year; in some cases e.g. Amara only the larvae overwinter and the adults will not be seen until late Spring, but the majority overwinter as adults or adults and larvae and so may be found early in the year. Many carabid species are stenotopic and so working a new biotope e.g. calcareous grassland or the seashore can be very rewarding. A few species are generally distributed in the U.K. and occur in many situations. In most species the body is elongate and to some extent flattened so accommodating a terrestrial lifestyle in soil crevices or under stones etc. Omophron is an exception, and burrowing species e.g. Clivina or Dyschirius are more convex and cylindrical. The hind wings are usually well developed and used mostly when moving between summer and winter sites. Two genera, Cicindela Linnaeus, 1758 and Bracteon Bedel, 1879, fly readily to catch prey. Some species of Carabus Linnaeus, 1758, as well as Cychrus caraboides (Linnaeus, 1758) are flightless, the hind wings being rudimentary and the elytra fused. Wing dimorphism is common. Among the carabids many are stenotopic and so working a new biotope e.g. calcareous grassland or the seashore can be very rewarding. A few species are generally distributed in the U.K. and occur in many situations. Most U.K. species are black or mostly drab in colour but there are exceptions and while, admittedly, most of our strikingly coloured species are rare, at least some should be found quite quickly e.g. Bembidion Latreille, 1802, Elaphrus Fabricius, 1775, Badister Clairville, 1806 and Harpalus affinis (Schrank, 1781).

Description

The general form is elongate and rather parallel with the head narrower than the pronotum, and the pronotum narrower than the elytra. The head is prognathous and sometimes elongate e.g. Stomis Clairville, 1806, Cychrus and Odacantha Paykull, 1798. A transverse fronto-clypeal suture is usually distinct. The anterior margin of the clypeus is sometimes toothed, as in Dyschirius. The frons may be furrowed beside, or in front of, the eyes e.g. Bembidion and Notiophilus Duméril, 1806, or there may be a furrow extending back and recurved behind the eyes as in the Trechini Bonelli, 1810. The antennae are 11-segmented, filiform and pubescent from the third or fourth segment. In Loricera the basal segments bear very long setae. They are inserted in front of the eyes outside the base of the mandibles except in the Cicindelinae Latreille, 1802 where they are placed on the dorsal surface behind the mandibles. The mouthparts are usually obvious from above; the mandibles are generally robust and may be toothed or asymmetrical as in e.g. Badister. Sometimes there is a seta on the outer edge of the mandibles, and this can be an important diagnostic character. The palps are generally well developed and sometimes exceptionally so e.g.in Cychrus, but in the Bembidiini Stephens, 1827 the apical segment of the maxillary palps is tiny. The pronotum is generally flat or only weakly convex, rarely cylindrical e.g. Drypta Latreille, 1796, bordered and with various surface sculpture and setiferous punctures which may be diagnostically important. The scutellum is visible in all but Omophron, its basal margin in line with the elytral base except in the Broscini Hope, 1838 and the Scaritini Bonelli, 1810.The elytra generally bear striae, at least to some extent, exceptions being some Carabus and Broscini. An abbreviated scutellary stria is usually present. In the Trechini the Sutural stria is recurved at the elytral apex. In most species the interstices bear setiferous punctures which are often diagnostic for a species or a group. The abdomen has 6 visible sternites except in the genus Brachinus Weber, 1801 where there are 7 or 8. The legs are long and slender in many species, less often so they are robust and well developed and sometimes, e.g. in Clivina, they are adapted for digging. The fore tibia generally has a deep notch on the inner margin which is used as an antennal cleaner, but there are exceptions e.g. Nebriini Laporte, 1834.The tarsi are always 5 segmented and generally without lobes, but in some plant climbing species, e.g. Demetrias Bonelli, 1810 or Drypta, the fourth segment is widely bilobed. The males of most species have dilated basal segments on the fore and sometimes also the middle tarsi.