''Georissus'', also called minute mud-loving beetles, is the only genus in the

beetle Beetles are insects that form the order Coleoptera (), in the superorder Endopterygota. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 400,000 describ ...

family Georissidae (or Georyssidae). They are tiny insects living in wet soil, often near water. They are found on every continent except Antarctica.

Characteristics

Georissidae are small beetles (length 1–2 mm). They have a broadly oval body whose outline is more or less interrupted between the

pronotum The prothorax is the foremost of the three segments in the thorax of an insect, and bears the first pair of legs. Its principal sclerites (exoskeletal plates) are the pronotum ( dorsal), the prosternum (ventral), and the propleuron (lateral) on e ...

and the

elytra An elytron (; ; , ) is a modified, hardened forewing of beetles (Coleoptera), though a few of the true bugs (Hemiptera) such as the family Schizopteridae are extremely similar; in true bugs, the forewings are called hemelytra (sometimes alterna ...

. The head and pronotum are granulate, the

prosternum The prothorax is the foremost of the three segments in the thorax of an insect, and bears the first pair of legs. Its principal sclerites (exoskeletal plates) are the pronotum (dorsal), the prosternum (ventral), and the propleuron (lateral) on ea ...

is rudimentary, without intercoxal processes. The anterior coxae and

trochanter A trochanter is a tubercle of the femur near its joint with the hip bone. In humans and most mammals, the trochanters serve as important muscle attachment sites. Humans are known to have three trochanters, though the anatomic "normal" includes ...

s are fused. The basal ventrite is very large.

Ecology

Species are generally found within mud and sand at the periphery of rivers and streams, but also occur in tropical rainforest

leaf litter Plant litter (also leaf litter, tree litter, soil litter, litterfall or duff) is dead plant material (such as leaves, bark, needles, twigs, and cladodes) that have fallen to the ground. This detritus or dead organic material and its constituent ...

. Species of ''Georissus'' are predators on invertebrates, and under laboratory conditions sometimes engage in cannibalism. Species within the genus are known for their habit of

psammophory Psammophory is a method by which certain plants armor themselves with sand on their body parts making chances less for them to be eaten by animals. Over 200 species of plants hailing from 88 genera in 34 families have been identified as psammorpho ...

(actively covering their elytra with sand or mud) which helps protect them against predators.

Systematics and evolution

There are about 75 living species, including: *'' Georissus australis'' *'' Georissus babai'' *'' Georissus bipartitus'' *'' Georissus caelatus'' *'' Georissus californicus'' *'' Georissus canalifer'' *''

Georissus capitatus ''Georissus'', also called minute mud-loving beetles, is the only genus in the beetle family Georissidae (or Georyssidae). They are tiny insects living in wet soil, often near water. They are found on every continent except Antarctica. Character ...

'' *'' Georissus coelosternus'' *''

Georissus costatus ''Georissus'', also called minute mud-loving beetles, is the only genus in the beetle family Georissidae (or Georyssidae). They are tiny insects living in wet soil, often near water. They are found on every continent except Antarctica. Character ...

'' *'' Georissus crenulatus'' *'' Georissus formosanus'' *'' Georissus fusicornis'' *'' Georissus granulosus'' *'' Georissus instabilis'' *'' Georissus japonicus'' *'' Georissus kingii'' *'' Georissus kurosawai'' *'' Georissus laesicollis'' *'' Georissus minusculus'' *'' Georissus occidentalis'' *'' Georissus pusillus'' *'' Georissus sakaii'' *'' Georissus septemcostatus'' *'' Georissus substriatus'' *'' Georissus trifossulatus'' The genus is divided into three subgenera (''Georissus'', ''Neogeorissus'' and ''Nipponogeorissus''). Formerly it was included within the family

Hydrophilidae Hydrophilidae, also known colloquially as water scavenger beetles, is a family of beetles. Aquatic hydrophilids are notable for their long maxillary palps, which are longer than their antennae. Several of the former subfamilies of Hydrophilidae ...

. Recent molecular data indicate, that they belong to a clade comprising the small groups of

Hydrophiloidea Hydrophiloidea, known as water scavenger beetles, is a superfamily of beetles. Until recently it included only a single family, the Hydrophilidae (water scavenger beetles), but several of the subfamilies have been removed and raised to family ra ...

- Epimetopidae, Hydrochidae, Helophoridae and Georissidae.D.Bernhard et al., From terrestrial to aquatic habitats and back again — molecular insights into the evolution and phylogeny of Hydrophiloidea (Coleoptera) using multigene analyses. Zoologica Scripta 35 (6), 597–606, 2006

References

Hydrophiloidea Staphyliniformia genera Taxa named by Pierre André Latreille {{Hydrophiloidea-stub