Carabids (as here treated) include all of the terrestrial adephagans other than trachypachids. This is by far the largest family of Adephaga, with over 30,000 described species. Among the more well-known members of the family are the genus Carabus (Carabini), bombardier beetles (Brachinini), and tiger beetles (Cicindelitae).
The vast majority of carabids are predacious. Most of theseare generalist predators, but there are a number of groups thathave become specialized (e.g., Peleciini and Promecognathini on millipedes, Cychrini and Licinini on snails). A few clades have larvae that are ectoparasitoids on other arthropods (e.g., Lebiini, Brachinitae, and Peleciini). Others are seed-eaters (e.g., Harpalini).
There are very few derived features that delimit carabids. In adults, the metacoxae are narrower than other adephagans, with the metapleuron extending posteriorly to contact the second abdominal sternite. There are also a few minor features in the head structure and musculature of larvae (see Beutel, 1995, for a summary).
This is a very large family of beetles, with over 26,000 species known from around the world, and many thousands probably not yet known. In Michigan there are as many as 450 species of Ground Beetles.
Biogeographic Regions: nearctic (Native ); palearctic (Native ); oriental (Native ); ethiopian (Native ); neotropical (Native ); oceanic islands (Native )
Ground Beetles are rather diverse in shape. Most adults are glossy and black, but some are iridescent, some are green, some are yellow or orange. Their bodies are usually flattened with grooves or rows of punctures running down the wing covers. They are usually a bit longer than wide, have long legs (for a beetle) and run fast. Larvae have large heads and are somewhat hairy.
Other Physical Features: ectothermic ; bilateral symmetry
Ground beetles are found in just about any habitat that has other small animals for them to eat. They are most diverse and common in forests, but can be found on high mountains, in deserts, even on the seashore.
Habitat Regions: temperate ; tropical ; terrestrial
Terrestrial Biomes: tundra ; taiga ; desert or dune ; chaparral ; forest ; rainforest ; scrub forest ; mountains
Wetlands: marsh ; swamp
Ground beetle larvae and adults are predators, eating other small animals. Some speciailze on a particular group (Gastropoda for example, or Lepidoptera) others will eat anything they can find.
Ground beetles have their tough beetle shell for protection. They run fast, and only hunt at night. Many can give off bad-tasting chemicals. One group, bombardier beetles, can shoot out boiling hot toxic chemicals from glands on their abdomen!
- other Coleoptera
Laboulbenia argutoris ectoparasitises live metasternum of Carabidae
Animal / parasite / ectoparasite
Laboulbenia polyphaga ectoparasitises live Carabidae
Animal / parasitoid / endoparasitoid
larva of Zaira cinerea is endoparasitoid of abdomen of imago of Carabidae
Known prey organisms
Based on studies in:
Costa Rica (Carrion substrate)
This list may not be complete but is based on published studies.
- L. F. Jiron and V. M. Cartin, 1981. Insect succession in the decomposition of a mammal in Costa Rica. J. New York Entomol. Soc. 89:158-165, from p. 163.
Life History and Behavior
Communication and Perception
Mostly by taste and smell, though they have large eyes, and no doubt do a lot of touching of things.
See page on all Beetles.
Development - Life Cycle: metamorphosis
Most species in this family mature in one year, and can live for 2-3.
After mating, female beetles lay eggs in the soil. They place them one by one, not in groups. They can lay many dozens of eggs over the summer.
Breeding season: Summer.
Key Reproductive Features: iteroparous ; seasonal breeding ; sexual ; fertilization (Internal ); oviparous
Males do not care for young. Females in some species place eggs in mud cells attached to plants or stones, others just hide the egg in the soil. Once the egg is laid (and possibly enclosed in the cell), the female leaves it alone.
Parental Investment: no parental involvement
Evolution and Systematics
Discussion of Phylogenetic Relationships
While carabid phylogeny has been extensively studied, the convergences and reversals present in morphological traits has lead to a great deal of controversy about many groups. Two of these groups, the tiger beetles (Cicindelitae) and wrinkled bark beetles (Rhysodini) are often considered outside the carabid clade. The phylogeny shown of carabid tribes on this and other pages is a conservative consensus view, in which a large number of "basal" groups give rise to a middle and upper grade of carabids. Within this latter group is a large, relatively uniform clade, the Harpalinae, which includes many of the larger, more common carabids.
Included below the tree are a number of especially enigmatic groups, including Gehringiini and Rhysodini, which may be older lineages, related to groups in this page, or they may instead be related to groups within the Carabidae Conjunctae. Their placement, along with the resolution of other aspects of carabid phylogeny, awaits numerical analysis of available morphological and molecular data.
The body surfaces of jewel beetles and other beetles create colors by reflecting lights at different wavelengths.
"The Buprestid beetles…as well as many ground-beetles (Carabidae), are different again in that the body surface producing the colour is hardened and quite permanent and sculptured into subtly varying shapes that reflect light at different wavelengths - blue, purple, green, bronze, silver and gold. The purple flush on the elytra of the ground-beetle, Carabus violaceus, is due to this cause, as are the metallic marks on various butterfly pupae." (Wootton 1984:140)
Learn more about this functional adaptation.
- Wootton, A. 1984. Insects of the World. Blandford. 224 p.
Molecular Biology and Genetics
Statistics of barcoding coverage
|Specimen Records:||19,994||Public Records:||4,856|
|Specimens with Sequences:||14,902||Public Species:||1,286|
|Specimens with Barcodes:||12,596||Public BINs:||854|
|Species With Barcodes:||1,780|
Locations of barcode samples
Relevance to Humans and Ecosystems
Economic Importance for Humans: Negative
A few species in this group attack seeds of corn as well as animal prey, but this is usually a minor factor.
Negative Impacts: crop pest
Economic Importance for Humans: Positive
This group of beetles is very important in controlling pests in the soil, especially the larvae of other insects.
Positive Impacts: controls pest population
|This article needs additional citations for verification. (February 2011)|
Description and ecology
Although their body shapes and coloring vary somewhat, most are shiny black or metallic and have ridged wing covers (elytra). The elytra are fused in some species, particularly large Carabinae, rendering the beetles unable to fly. The genus Mormolyce is known as violin beetles due to their peculiarly shaped elytra. All carabids except the quite primitive flanged bombardier beetles (Paussinae) have a groove on their foreleg tibiae bearing a comb of hairs used for cleaning their antennae.
Typical for the ancient beetle suborder Adephaga to which they belong, they have paired pygidial glands in the lower back of the abdomen. These are well developed in ground beetles, and produce noxious or even caustic secretions used to deter would-be predators. In some, commonly known as bombardier beetles, these secretions are mixed with volatile compounds and ejected by a small combustion, producing a loud popping sound and a cloud of hot and acrid gas which can injure small mammals, such as shrews, and is liable to kill invertebrate predators outright. To humans, getting "bombed" by a bombardier beetle is a decidedly unpleasant experience. This ability has evolved independently twice as it seems – in the flanged bombardier beetles (Paussinae) which are among the most ancient ground beetles, as well as in the typical bombardier beetles (Brachininae) which are part of a more "modern" lineage. The Anthiini, meanwhile, can mechanically squirt their defensive secretions for considerable distances and are able to aim with a startling degree of accuracy; in Afrikaans they are known as oogpisters ("eye-pissers"). In one of the very few known cases of a vertebrate mimicking an arthropod, juvenile Heliobolus lugubris lizards are colored similar to the aposematic oogpister beetles, and move in a way that makes them look surprisingly similar to the insects at a casual glance.
Charles Darwin may have found himself on the receiving end of a bombardier beetle's defences on a collecting trip in 1828, but this is based on a misreading of his autobiography;[not in citation given] a bombardier beetle's "bombing" is already triggered by picking it up, and Darwin had been carrying the beetle in question in his closed hand for some time already before he ran afoul of its secretions. He discussed this incident and another such case in a letter to Leonard Jenyns as follows:
A Cychrus rostratus once squirted into my eye & gave me extreme pain; & I must tell you what happened to me on the banks of the Cam in my early entomological days; under a piece of bark I found two carabi (I forget which) & caught one in each hand, when lo & behold I saw a sacred Panagæus crux major; I could not bear to give up either of my Carabi, & to lose Panagæus was out of the question, so that in despair I gently seized one of the carabi between my teeth, when to my unspeakable disgust & pain the little inconsiderate beast squirted his acid down my throat & I lost both Carabi & Panagæus!
Common habitats are under the bark of trees, under logs, or among rocks or sand by the edge of ponds and rivers. Most species are carnivorous and actively hunt for any invertebrate prey they can overpower. Some will run swiftly to catch their prey; tiger beetles (Cicindelinae) can sustain speeds of 8 km/h (5 mph) – in relation to their body length they are among the fastest land animals on Earth. Unlike most Carabidae which are nocturnal, the tiger beetles are active diurnal hunters and often brightly coloured; they have large eyes and hunt by sight. Ground beetles of the species Promecognathus laevissimus are specialised predators of the cyanide millipede Harpaphe haydeniana, countering the hydrogen cyanide which makes these millipedes poisonous to most carnivores.
Relationship with humans
As predators of invertebrates, including many pests, most ground beetles are considered beneficial organisms. The caterpillar hunters (Calosoma) are famous for their habit of devouring prey in quantity, eagerly feeding on tussock moth (Lymantriidae) caterpillars, processionary caterpillars (Thaumetopoeidae) and woolly worms (Arctiidae), which due to their urticating hairs are avoided by most insectivores. Large numbers of the Forest Caterpillar Hunter (C. sycophanta), native to Europe, were shipped to New England for biological control of the gypsy moth (Lymantria dispar) as early as 1905.
A few species are nuisance pests. Zabrus is one of the few herbivorous ground beetle genera, and on rare occasions Zabrus tenebrioides for example occurs abundantly enough to cause some damage to grain crops. Large species, usually Carabinae, can become a nuisance if present in numbers, particularly during outdoor activities such as camping; they will void their defensive secretions when threatened, and if they hide among provisions this can despoil food. Since ground beetles are generally reluctant or even unable to fly, it is usually easy to block their potential routes of entry mechanically or with a topical insecticide.
Especially in the 19th century and to a lesser extent today, their large size and conspicuous coloration as well as the odd morphology of some (e.g. the Lebiini) made many ground beetles a popular object of collection and study for professional and amateur coleopterologists. High prices were paid for rare and exotic specimens, and in the early to mid-19th century there was a veritable "beetle craze" in England. As mentioned above, Charles Darwin was an ardent collector of beetles when he was about twenty years old, to the extent that he'd rather scour the countryside for rare specimens with William Darwin Fox, John Stevens Henslow and Henry Thompson than to study theology as his father wanted him to do. In his autobiography he fondly recalled his experiences with Licinus and Panagaeus, and wrote:
No poet ever felt more delight at seeing his first poem published than I did at seeing in Stephen's Illustrations of British Insects the magic words, "captured by C. Darwin, Esq."
Evolution and systematics
|This article is outdated. (October 2011)|
The Adephaga are documented since the end of the Permian, about . Ground beetles evolved in the latter Triassic, having separated from their closest relatives by . The family diversified throughout the Jurassic, and the more advanced lineages, such as the Harpalinae, underwent a vigorous radiation starting in the Cretaceous. The closest living relatives of the ground beetles are the false ground beetles (Trachypachidae) and the wrinkled bark beetles (Rhysodidae). They are sometimes even included in the Carabidae as subfamilies or as tribes incertae sedis, but more preferably they are united with the ground beetles in the superfamily Caraboidea.
Much research has been done on elucidating the phylogeny of the ground beetles and adjusting systematics and taxonomy accordingly. While there is no completely firm consensus, a few points are generally accepted: As it seems, the ground beetles consist of a number of more basal lineages and the extremely diverse Harpalinae which contain over half the described species and into which several formerly independent families had to be subsumed.
Subfamilies and selected genera
The taxonomy used here is based on the Catalogue of Palaearctic Coleoptera and the Carabidae of the World Database. Other classifications, while generally agreeing with the division into a basal radiation of more primitive lineages and the more advanced group informally called "Carabidae Conjunctae", differ in details. For example, the system used by the Tree of Life Web Project makes little use of subfamilies, listing most tribes as incertae sedis as to subfamily. Fauna Europaea on the other hand splits rather than lumps the Harpalinae, restricting them to what in the system uses here is the tribe Harpalini.
All the approaches mentioned above are legitimate as they agree with the phylogeny as far as it has been resolved. The inclusive Harpalinae presented here are used for two reasons, one scientific and one practical – first, the majority of authors presently uses this system, following the Catalogue of Palaearctic Coleoptera. Second, the MediaWiki markup cannot at present adequately represent the relationships of the ground beetle subgroups in detail if the restricted view of the Harpalinae is chosen.
Basal ground beetles
- Aplothorax (monotypic genus)
- Calosoma - including Callisthenes
Elaphrinae Latreille, 1802
Loricerinae Bonelli, 1810
Omophroninae Bonelli, 1810 – round sand beetles
Paussinae – ant nest beetles, flanged bombardier beetles
Scaritinae Bonelli, 1810 – pedunculate ground beetles
Siagoninae Bonelli, 1810
Brachininae – typical bombardier beetles
Tribes incertae sedis
- Amarotypini – Migadopinae or a distinct subfamily?
- Gehringiini – Psydrinae, Trechinae or a distinct subfamily?
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Bombardier beetles are ground beetles (Carabidae) in the tribes Brachinini, Paussini, Ozaenini, or Metriini—more than 500 species altogether—which are most notable for the defense mechanism that gives them their name: when disturbed, they eject a hot noxious chemical spray from the tip of their abdomen, with a popping sound.
The spray is produced by a reaction between two chemical compounds, hydroquinone and hydrogen peroxide, stored in separate reservoirs in the beetle's abdomen and mixed when needed in a third chamber with water and catalytic enzymes. Heat from the reaction brings the mixture to near the boiling point of water and produces gas that drives the ejection. The damage caused can be fatal to attacking insects and small creatures and is painful to human skin. Some bombardier beetles can direct the spray over a wide range of directions.
Bombardier beetles inhabit most of the continents, with the exception of Antarctica. They typically live in woodlands or grasslands in the temperate zones but can be found in other environments if there are moist places to lay their eggs.
Most species of bombardier beetles are carnivorous, including the larva. The beetle typically hunts at night for other insects, but will often congregate with others of its species when not actively looking for food.
The two reactant chemical compounds, hydroquinones and hydrogen peroxide, are secreted by specialized glands and are stored in separate reservoirs in the rear tip of its abdomen. When threatened, the beetle contracts muscles that open the valves of these reservoirs and force the two reactants into a thick-walled mixing chamber lined with cells that produce enzymes including catalases and peroxidases.
In the mixing chamber the enzymes rapidly break down the hydrogen peroxide, releasing free oxygen and catalyzing the oxidation of the hydroquinones into p-quinones. The reaction is very exothermic, and the released energy raises the temperature of the mixture to near 100 °C, vaporizing about a fifth of it. The resultant pressure buildup forces the entrance valves from the reactant storage chambers to close, thus protecting the beetle's internal organs. The boiling, foul-smelling liquid partially becomes a gas by flash evaporation and is expelled explosively through an outlet valve, with a loud popping sound.
The flow of reactants into the reaction chamber and subsequent ejection occur in a series of about 70 pulses, at a rate of about 500 pulses per second. The whole sequence of events takes only a fraction of a second.
Typically the beetle turns its body so as to direct the jet towards whatever triggered the response. The gland openings of some African bombardier beetles can swivel through 270° and thrust between the insect's legs, discharging the fluid in a wide range of directions with considerable accuracy.
Evolution of the defense mechanism
The unique combination of features of the bombardier beetle's defense mechanism—strongly exothermic reactions, boiling-hot fluids, and explosive release—have been used by creationists and proponents of intelligent design as examples of irreducible complexity that could not have been produced by evolution. However, while the true evolutionary path is still unknown, biologists have shown that the system could in fact have evolved from defenses found in other beetles in incremental steps by natural selection.
Specifically, quinone chemicals are a precursor to sclerotin, a brownish substance produced by beetles and other insects to harden their exoskeleton. Some beetles additionally store excess foul-smelling quinones, including hydroquinone, in small sacs below their skin as a natural deterrent against predators—all carabid beetles have this sort of arrangement. Some beetles additionally mix hydrogen peroxide, a common by-product of the metabolism of cells, in with the hydroquinone, and some of the catalases that exist in most cells makes the process more efficient. The chemical reaction produces heat and pressure, and some beetles exploit the latter to push out the chemicals onto the skin; this is the case in the beetle Metrius contractus, which produces a foamy discharge when attacked. In the bombardier beetle, the muscles that prevent leakage from the reservoir additionally developed a valve permitting more controlled discharge of the poison and an elongated abdomen to permit better control over the direction of discharge.
- Poecilocerus pictus, a grasshopper from India; squirts liquid several inches for defense.
- Parasanaa donovani, a grasshopper from north India, squirts a yellow slimy liquid several inches 
- Aularches miliaris, a grasshopper from Myanmar, forcefully ejects a foamy sticky liquid when pressed.
- Tegra novaehollandiae, a grasshopper, secretes yellow liquid when slightly pressed.
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