''Gaius'' is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of large

mygalomorph The Mygalomorphae, or mygalomorphs, are an infraorder of spiders, and comprise one of three major groups of living spiders with over 3000 species, found on all continents except Antarctica. Many members are known as trapdoor spiders due to the ...

spider Spiders ( order Araneae) are air-breathing arthropods that have eight legs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude silk. They are the largest order of arachnids and rank seventh in total species ...

s in the family

Idiopidae Idiopidae, also known as armored trapdoor spiders, is a family of mygalomorph spiders first described by Eugène Simon in 1889. They have a large body similar to tarantulas. Description In some species the males have a spur on their legs, which ...

. Erected in 1914 by

William Joseph Rainbow William Joseph Rainbow (1856–1919) was an entomologist and arachnologist whose work includes the first catalogue of Australian spiders. Life Rainbow was born in 1856 in Yorkshire, England. His father was a Warrant Officer in the Royal Marines, ...

, for much of its history the genus contained only one species, ''

Gaius villosus ''Gaius villosus'' is a species of spider in the family Idiopidae (armored trapdoor spiders) found in Western Australia in a variety of different habitats. Originally described in 1914 as ''Gaius villosus'' by William Joseph Rainbow, in 1957 it ...

''. More species were added in 2018. All are endemic to

Western Australia Western Australia (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to th ...

Description

Species of ''Gaius'' are large spiders, usually dark brown or black. Females have a body length of around , males around . The

carapace A carapace is a Dorsum (biology), dorsal (upper) section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tor ...

has a dense fringe of hairs (setae) along the sides. The

abdomen The abdomen (colloquially called the belly, tummy, midriff, tucky or stomach) is the part of the body between the thorax (chest) and pelvis, in humans and in other vertebrates. The abdomen is the front part of the abdominal segment of the torso. ...

is oval, densely covered with hairs. Males have

pedipalp Pedipalps (commonly shortened to palps or palpi) are the second pair of appendages of chelicerates – a group of arthropods including spiders, scorpions, horseshoe crabs, and sea spiders. The pedipalps are lateral to the chelicerae ("jaws") and ...

s with a

retrolateral tibial apophysis This glossary describes the terms used in formal descriptions of spiders; where applicable these terms are used in describing other arachnids. Links within the glossary are shown . Terms A Abdomen or opisthosoma: One of the two main body parts ...

(RTA), which in most species is large and long. Females have a pair of simple, widely spaced

spermathecae The spermatheca (pronounced plural: spermathecae ), also called receptaculum seminis (plural: receptacula seminis), is an organ of the female reproductive tract in insects, e.g. ants, bees, some molluscs, oligochaeta worms and certain other in ...

Taxonomy

The genus ''Gaius'' was erected by

in 1914 for his new species ''Gaius villosus''. In 1957,

Barbara York Main Barbara Anne York Main (27 January 1929 – 14 May 2019) Ann Jones (2019"Barbara York Main, Australia's spider woman and Wheatbelt advocate, author and poet dies"''Off Track'', Australian Broadcasting Corporation. Published May 23, 2019. Acces ...

transferred ''G. villosus'' (then still the only species of ''Gaius'') to the genus ''Anidiops'', noting the inadequacy of many characters used in

taxonomy Taxonomy is the practice and science of categorization or classification. A taxonomy (or taxonomical classification) is a scheme of classification, especially a hierarchical classification, in which things are organized into groups or types. ...

. Main placed the species in the tribe Aganippini, within the family Ctenizidae (as then circumscribed). (Rainbow had used the same placement, although with different ranks.) By 2017, the Ctenizidae had been split, and the tribe Aganippini was placed in the subfamily Arbanitinae of the family

. A major study of the Arbanitinae, including

molecular phylogenetic Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...

evidence, concluded that ''Gaius'' was a distinct genus, although all the other species of ''Anidiops'' were placed in the genus ''

Idiosoma ''Idiosoma'' is a genus of Australian armored trapdoor spiders that was first described by Anton Ausserer in 1871. Originally placed with the Ctenizidae, it was moved to the armored trapdoor spiders in 1985. The name is derived from the Greek ...

''. ''Gaius'' remained a

monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unispec ...

genus until 2018, when a further seven species were added.

Phylogeny

Within the tribe Aganippini, ''Gaius'' is sister to the genus '' Eucyrtops'':

Species

, the

World Spider Catalog The World Spider Catalog (WSC) is an online searchable database concerned with spider taxonomy. It aims to list all accepted families, genera and species, as well as provide access to the related taxonomic literature. The WSC began as a series of ...

accepted the following species: *'' Gaius aurora'' Rix, Raven & Harvey, 2018 – Australia (Western Australia) *'' Gaius austini'' Rix, Raven & Harvey, 2018 – Australia (Western Australia) *'' Gaius cooperi'' Rix, Raven & Harvey, 2018 – Australia (Western Australia) *'' Gaius hueyi'' Rix, Raven & Harvey, 2018 – Australia (Western Australia) *'' Gaius humphreysi'' Rix, Raven & Harvey, 2018 – Australia (Western Australia) *'' Gaius mainae'' Rix, Raven & Harvey, 2018 – Australia (Western Australia) *'' Gaius tealei'' Rix, Raven & Harvey, 2018 – Australia (Western Australia) *''

'' Rainbow, 1914 (

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...

) – Australia (Western Australia)

Distribution and habitat

''Gaius'' species are found in a broad region in the south-west of Western Australia. They are most common in mallee woodlands, ''

Acacia ''Acacia'', commonly known as the wattles or acacias, is a large genus of shrubs and trees in the subfamily Mimosoideae of the pea family Fabaceae. Initially, it comprised a group of plant species native to Africa and Australasia. The genus na ...

'' (mulga) woodlands and shrublands, and spinifex ('' Triodia'') plains, where the soil is clay or hard loam. They construct deep burrows with a flap- or wafer-like door.

References

Mygalomorphae genera Idiopidae Taxa named by William Joseph Rainbow Spiders described in 1914 {{Mygalomorphae-stub