Ground beetles are a large,cosmopolitanfamily ofbeetles,[2] theCarabidae, with more than 40,000 species worldwide, around 2,000 of which are found inNorth America and 2,700 inEurope.[3] As of 2015, it is one of the 10 most species-rich animal families. They belong to the suborderAdephaga. Members of the family are primarilycarnivorous, but some members areherbivorous oromnivorous.[4]
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 somespecies, particularly the largeCarabinae, rendering the beetles unable to fly. ThespeciesMormolyce phyllodes is known as violin beetle due to their peculiarly shaped elytra. All carabids except the quite primitiveflanged bombardier beetles (Paussinae) have a groove on theirfore leg tibiae bearing a comb of hairs used for cleaning theirantennae.[5]
Typical for the ancient beetlesuborderAdephaga to which they belong, they have pairedpygidialglands in the lower back of theabdomen. These are well developed in ground beetles, and produce noxious or evencaustic secretions used to deter would-bepredators. In some, commonly known asbombardier beetles, these secretions are mixed withvolatile compounds and ejected by a smallcombustion, producing a loud popping sound and a cloud of hot and acrid gas that can injure smallmammals, such asshrews, and is liable to killinvertebrate predators outright.
To humans, getting "bombed" by a bombardier beetle is a decidedly unpleasant experience.[citation needed] This ability hasevolved independently twice, as it seems, in theflanged bombardier beetles (Paussinae), which are among the most ancient ground beetles, and in the typical bombardier beetles (Brachininae), which are part of a more "modern" lineage. TheAnthiini, though, can mechanically squirt their defensive secretions for considerable distances and are able to aim with a startling degree of accuracy; inAfrikaans, they are known asoogpisters ("eye-pissers"). In one of the very few known cases of avertebratemimicking anarthropod, juvenileHeliobolus lugubrislizards are similar in color to theaposematicoogpister beetles, and move in a way that makes them look surprisingly similar to the insects at a casual glance.[6]
A folk story claims thatCharles Darwin once found himself on the receiving end of a bombardier beetle's attack, based on a passage in his autobiography.[7][8] Darwin stated in a letter toLeonard Jenyns that a beetle had attacked him on that occasion, but he did not know what kind:
ACychrus rostratus once squirted into my eye & gave me extreme pain; & I must tell you what happened to me on the banks of theCam 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 sacredPanagæus crux major; I could not bear to give up either of my Carabi, & to losePanagæus 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![9]
Commonhabitats are under the bark of trees, under logs, or among rocks[2] or sand by the edge of ponds and rivers. Most species arecarnivorous and actively hunt for anyinvertebrate prey they can overpower.[2] Some run swiftly to catch their prey;tiger beetles (Cicindelinae) can sustain speeds of 9 km/h (5.6 mph)[10] – in relation to their body length they are among the fastest land animals on Earth. Unlike most Carabidae, which arenocturnal, the tiger beetles are active diurnal hunters and often brightly coloured; they have large eyes and hunt by sight. Ground beetles of the genusPromecognathus are specialised predators of the cyanide millipedesHarpaphe haydeniana andXystocheir dissecta, countering thehydrogen cyanide that makes these millipedes poisonous to most carnivores.
A few species are nuisance pests.Zabrus is one of the fewherbivorous ground beetle genera, and on rare occasionsZabrus tenebrioides, for example, occurs abundantly enough to cause some damage tograin crops.[11] Large species, usually theCarabinae, can become a nuisance if present in large numbers, particularly during outdoor activities such ascamping; they void their defensive secretions when threatened, and in hiding among provisions, their presence may spoil food. Since ground beetles are generally reluctant or even unable to fly, mechanically blocking their potential routes of entry is usually easy. The use ofinsecticides specifically for carabid intrusion may lead to unfortunate side effects, such as the release of their secretions, so it generally is not a good idea unless the same applications are intended to exclude ants, parasites or other crawling pests.
Especially in the 19th century and to a lesser extent today, their large size and conspicuous coloration, as well as the oddmorphology of some (e.g. theLebiini), made many ground beetles a popular object of collection and study for professional and amateurcoleopterologists. High prices were paid for rare and exotic specimens, and in the early to mid-19th century, a veritable "beetle craze" occurred in England. As mentioned above, Charles Darwin was an ardent collector of beetles when he was about 20 years old, to the extent that he would rather scour the countryside for rare specimens withWilliam Darwin Fox,John Stevens Henslow, andHenry Thompson than to studytheology as his father wanted him to do. In his autobiography, he fondly recalled his experiences withLicinus andPanagaeus, and wrote:
No poet ever felt more delight at seeing his first poem published than I did at seeing in Stephen'sIllustrations of British Insects the magic words, "captured by C. Darwin, Esq."[8]
TheAdephaga are documented since the end of thePermian, about250 million years ago (Mya). Ground beetlesevolved in the latterTriassic, having separated from their closest relatives by 200 Mya. The family diversified throughout theJurassic, and the more advanced lineages, such as theHarpalinae, underwent a vigorous radiation starting in theCretaceous. The closest living relatives of the ground beetles are thefalse ground beetles (Trachypachidae) and thetiger beetles (Cicindelidae). They are sometimes even included in the Carabidae as subfamilies or as tribesincertae sedis, but more preferably they are united with the ground beetles in thesuperfamilyCaraboidea, orGeadephaga.[12]
Much research has been done on elucidating thephylogeny of the ground beetles and adjustingsystematics andtaxonomy accordingly. While no completely firm consensus exists, a few points are generally accepted: The ground beetles seemingly consist of a number of morebasal lineages and the extremely diverse Harpalinae, which contain over half the described species and into which several formerly independent families had to be subsumed.[13]
The taxonomy used here is primarily based on the Catalogue of Life and the Carabcat 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",[14] differ in details. For example, the system used by theTree of Life Web Project makes little use of subfamilies, listing mosttribes asincertae sedis as to subfamily.[15]Fauna Europaea, though,splits rather than lumps the Harpalinae, restricting them to what in the system used here is the tribeHarpalini.[16] The exclusion of Trachypachidae as a separate family is now amply supported, as is the inclusion of Rhysodidae as a subfamily, closely related toPaussinae andSiagoninae.[12]
The exclusive Harpalinae is presented here, because the majority of authors presently use this system, following theCarabidae of the World,Catalogue of Palaearctic Coleoptera, or theCarabcat Database[17] (which is reflected theCatalogue of Life).[18]
Tiger Beetles have historically been treated as a subfamily of Carabidae under the name Cicindelinae, but several studies since 2020 indicated that they should be treated as a family, Cicindelidae, a sister group to Carabidae.[12]
^abcVasilikopoulos, A., Balke, M., Kukowka, S., Pflug, J.M., Martin, S., Meusemann, K., Hendrich, L., Mayer, C., Maddison, D.R., Niehuis, O., Beutel, R.G. and Misof, B. (2021), Phylogenomic analyses clarify the pattern of evolution of Adephaga (Coleoptera) and highlight phylogenetic artefacts due to model misspecification and excessive data trimming. Syst Entomol, 46: 991-1018.https://doi.org/10.1111/syen.12508
^Shōzō Ōsawa, Zhi-Hui Su & Yūki Inmura (2004).Molecular Phylogeny and Evolution of Carabid Ground Beetles.Springer.ISBN4-431-00487-4.
E. Csiki (1946).Die Käferfauna des Karpaten-Beckens [The beetle fauna of the Carparthian basin] (in German). Budapest. pp. 71–546.{{cite book}}: CS1 maint: location missing publisher (link)
K. Kult (1947).Klíč k určování brouků čeledi Carabidae Československé republiky [Key to the beetles of family Carabidae of the Czech Republic] (in Czech). Prague.{{cite book}}: CS1 maint: location missing publisher (link)
C. H. Lindroth (1942).Coleoptera, Carabidae. Svensk Insectenfauna, Vol. 9 (in Swedish). Stockholm. pp. 1–260.{{cite book}}: CS1 maint: location missing publisher (link)
Edmund Reitter (1908–1917).Die Käfer des Deutschen Reiches [The beetles of the German Empire] (in German). Stuttgart: K. G. Lutz.
