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 ...

species ''Plebs eburnus'' is commonly referred to as the eastern grass orb-weaver or the eastern bush orb-weaver, and sometimes more simply as the bush orb-weaver. It is an

orb-weaver spider Orb-weaver spiders are members of the spider family Araneidae. They are the most common group of builders of spiral wheel-shaped webs often found in gardens, fields, and forests. The English word "orb" can mean "circular", hence the English name ...

from the family Araneidae endemic to

Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...

. It is a very common spider with distinctive white markings (although these marking can be quite variable), which give it the species name ''eburnus'' pertaining to ivory. It is found in scrub and tall grasses where the female constructs a vertical web usually no more than 2 metres from the ground, and stays there day and night. The web of some of these spiders has been seen to be decorated with nearly vertical

stabilimentum A stabilimentum (plural: stabilimenta), also known as a web decoration, is a conspicuous silk structure included in the webs of some species of orb-web spider. Its function is a subject of debate. Origin It is likely that the use of stabiliment ...

(like a clockface at 5 minutes to 5 or its mirror image). The stabilimentum of the related ''P.cyphoxis'' is usually observed vertical (like a clockface at 6 o'clock).

Description

On the underside of 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. ...

, along with other members of the genus ''

Plebs In ancient Rome, the plebeians (also called plebs) were the general body of free Roman citizenship, Roman citizens who were not Patrician (ancient Rome), patricians, as determined by the capite censi, census, or in other words "commoners". Both ...

'', there is a characteristic U-shaped white marking with two white spots either side of the

spinnerets A spinneret is a silk-spinning organ of a spider or the larva of an insect. Some adult insects also have spinnerets, such as those borne on the forelegs of Embioptera. Spinnerets are usually on the underside of a spider's opisthosoma, and are ...

. The females, as with most spiders, are larger than the males and are around 8mm in length, compared to just 5mm in length for the males.

Taxonomy

The species was first described by

Eugen von Keyserling Eugen von Keyserling (22 March 1833 in Pockroy, Lithuania – 4 April 1889 in Dzierżoniów, Silesia) was a Baltic-German arachnologist. He studied in the University of Tartu. He was the author of ''Die Spinnen Amerikas'', and completed ''Die Ara ...

in 1886 as ''Epeira eburna''. It was transferred to the genus ''

Araneus ''Araneus'' is a genus of common orb-weaving spiders. It includes about 650 species, among which are the European garden spider and the barn spider. The genus was erected by Carl Alexander Clerck in 1757. Description Spiders of this genus prese ...

'' and then in 2012 into a newly described genus ''

''. It is closely related to the western bush orb-weaver, '' P. cyphoxis''.

Distribution

''P. eburnus'' can be found in Queensland, New South Wales, Victoria, Tasmania, Australian Capital Territory and South Australia. Some rare occurrences have been observed in Western Australia although this is not part of the typical range of this species. The ranges of this species and ''P. cyphoxis'' overlap in South Australia.

References

{{Taxonbar, from1=Q27447187, from2=Q1842867 Araneidae Spiders of Australia Spiders described in 1886