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

beetle Beetles are insects that form the Taxonomic rank, order Coleoptera (), in the superorder Holometabola. Their front pair of wings are hardened into wing-cases, elytra, distinguishing them from most other insects. The Coleoptera, with about 40 ...

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 (; ; : elytra, ) 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 (sometime ...

. 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 e ...

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 have two, sometimes three, trochanters. Etymology The anatomical term ' ...

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 has fallen to the ground. This detritus or dead organic material and its constituen ...

. 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 also well document ...

. Species within the genus are known for their habit of psammophory (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'', also called minute mud-loving beetles, is the only genus in the beetle Beetles are insects that form the Taxonomic rank, order Coleoptera (), in the superorder Holometabola. Their front pair of wings are hardened into wing- ...

'' *'' Georissus canalifer'' *'' Georissus capitatus'' *'' 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 ...

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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 pusillus'' *''

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

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

Hydrophiloidea Hydrophiloidea, known as water scavenger beetles, is a Taxonomic rank, 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 rais ...

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 ''Hydrochus'' is the only living genus of beetle in the family Hydrochidae, which belongs to the superfamily Hydrophiloidea, and was formerly treated as a subfamily of Hydrophilidae. ''Hydrochus'' includes about 180 species, which are found worldw ...

, 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