''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.

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 and the elytra. 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 trochanters 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. Species of ''Georissus'' are predators on invertebrates, and under laboratory conditions sometimes engage in

cannibalism Cannibalism is the act of consuming another individual of the same species as food. Cannibalism is a common ecological interaction in the animal kingdom and has been recorded in more than 1,500 species. Human cannibalism is well documented, b ...

. 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'', 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 bipartitus'' *''

Georissus caelatus ''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 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'', 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 formosanus ''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 fusicornis ''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 granulosus ''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 instabilis ''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 japonicus ''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 kingii ''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 kurosawai ''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 laesicollis ''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 minusculus ''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 occidentalis ''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 pusillus ''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 sakaii ''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 septemcostatus ''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 substriatus ''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 trifossulatus ''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 ...

'' The genus is divided into three subgenera (''Georissus'', ''Neogeorissus'' and ''Nipponogeorissus''). Formerly it was included within the family Hydrophilidae. Recent

molecular A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bioche ...

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 Epimetopidae is a family of semi-aquatic beetles belonging to the Hydrophiloidea. They are found in sand and gravel at the edges of streams, rivers and shallow freshwater ponds. These beetles are shorter than half a centimeter long and have a pro ...

, 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