Australian jewel spider (Austracantha minax)

The Australian jewel spider (Austracantha minax) belongs to the distinctive orb-weaver family, and is beautifully ornamented with spines and circular impressions on the abdomen ⁽³⁾. As in all spiders the body is divided into two parts, the cephalothorax and the abdomen, and on each side of the mouth are venom-injecting fangs and leg-like pedipalps ⁽⁴⁾.

Spiders of the Austracantha genus have brightly coloured abdomens, usually red, yellow or white, the patterns of which deter predators such as birds. As in other members of its genus, female Australian jewel spiders have a hard body ⁽⁵⁾, with yellow and white patterning and a series of black spines. However, the melanic female morph is often completely black ⁽⁶⁾. Male orb-weaver spiders, including the Australian jewel spider, are smaller with a more cylindrical abdomen ⁽⁵⁾, and have a colourful yellow, white, brown and black body with smaller spines compared to the female. Both sexes have six spines that extend from the end of the abdomen ⁽⁶⁾.

There are five recognised subspecies of the Australian jewel spider ⁽¹⁾.

Also known as

Christmas spider, spiny spider.

Size

Male length: 3 mm ⁽²⁾

Female length: 7 - 10 mm ⁽²⁾

The Australian jewel spider builds its orb-shaped web from silk ⁽²⁾, placing silky ‘tufts’ on specific threads as it does so ⁽⁷⁾. All spiders are predatory and carnivorous, feeding by injecting venom into their insect prey ⁽⁸⁾. As an opportunistic feeder, the Australian jewel spider has a web which is extremely well adapted to catch flying insects ⁽⁹⁾.

Female and juvenile Australian jewel spiders spin orb webs solitarily or occasionally in groups, which are known as ‘facultative aggregations’. The potential advantages of facultative aggregations are increased protection from predators, increased prey capture, and greater mate choice for females. Associated costs can include increased parasitism of egg cases. The collective webs of the Australian jewel spider are often made up of up to 30 individual webs that are joined together by shared support threads ⁽²⁾.

When courting a female, the male Australian jewel spider begins by building a ‘mating thread’ from the vegetation to the edge of the female’s web, and strumming it using the first and second pair of legs. The female spider is enticed onto the mating thread by the strumming, and is then tightly embraced by the male, who passes sperm to the female’s external genital structure via a pedipalp ⁽¹⁰⁾. The male Australian jewel spider will defend the female following mating, ceasing only when the female is no longer receptive to mating ⁽¹¹⁾.

The variably shaped egg sacs of the Australian jewel spider are reddish-brown, and are usually found attached to a twig, close to the web ⁽⁶⁾. Australian jewel spiderlings pass through the Australian winter season within the camouflaged egg sacs, emerging in early spring. Male spiders reach maturity by mid-December whereas females mature later, in mid-January ⁽²⁾.

The Australian jewel spider is widespread throughout Australia ⁽²⁾.

The Australian jewel spider occurs in both tropical and temperate regions of Australia ⁽²⁾. Like all members of the Austracantha genus, this species generally builds its webs between shrub branches or on buildings ⁽⁵⁾.

The Australian jewel spider is not yet classified on the IUCN Red List.

There are no known threats to the Australian jewel spider at present.

No conservation actions are known to currently involve the Australian jewel spider. 

Find out more about the Australian jewel spider:

• ClimateWatch - Australian jewel spider:
  http://www.climatewatch.org.au/species/spiders/christmas-or-jewel-spider

For more information on conservation in Australia:

• Australian Wildlife Conservancy: 
  
  http://www.australianwildlife.org/
• Australian Conservation Foundation: 
  
  http://www.acfonline.org.au/

This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
arkive@wildscreen.org.uk

Abdomen

In arthropods (crustaceans, insects and arachnids) the abdomen is the hind region of the body, which is usually segmented to a degree (but not visibly in most spiders).

Carnivorous

Feeding on flesh.

Cephalothorax

The fused head and thorax (the part of the body located near the head).

Genus

A category used in taxonomy, which is below ‘family’ and above ‘species’. A genus tends to contain species that have characteristics in common. The genus forms the first part of a ‘binomial’ Latin species name; the second part is the specific name.

Melanism

The development of dark-coloured pigment in the skin or appendages.

Morph

One of two or more distinct types of a given species, often distinct colour forms, which occur in the same population at the same time (that is, are not geographical or seasonal variations).

Parasitism

Interaction in which one organism derives its food from, and lives in or on, another living organism (the host) at the host's expense.

Pedipalps

In arachnids (a group which includes spiders and scorpions), a pair of appendages which are modified for many uses, such as killing and manipulating prey, mating, defence and sensory perception.

Subspecies

A population usually restricted to a geographical area that differs from other populations of the same species, but not to the extent of being classified as a separate species.

1. Integrated Taxonomic Information System (ITIS) (November, 2012)
   http://www.itis.gov/
2. Lloyd, N. and Elgar, M. (1997) Costs and benefits of facultative aggregating behaviour in the orb-spinning spider Gasteracantha minax Thorell (Araneae: Araneidae). Australian Journal of Ecology. 22: 256-261.
3. Barrion, A. and Litsinger, J. (1995) Riceland Spiders of South and Southeast Asia. CAB International, Wallingford.
4. Burnie, D. (2001) Animal. Dorling Kindersley, London.
5. Hogue, C. (1993) Latin American Insects and Entomology. University of California Press, Berkeley.
6. ClimateWatch - Christmas or Jewel Spider (November, 2012)
   http://www.climatewatch.org.au/species/spiders/christmas-or-jewel-spider
7. Walter, A. and Elgar, M. (2012) The evolution of novel animal signals: silk decorations as a model system. Biological Reviews. 87: 686-700.
8. O’Toole, C. (2002) The New Encyclopedia of Insects and Their Allies. Oxford University Press, Oxford.
9. Lindenmayer, D., Crane, M., Michael, D. and Beaton, E. (2005) Woodlands: A Disappearing Landscape. CSIRO Publishing, Collingwood, Australia.
10. Elgar, M. and Bathgate, R. (1996) Female receptivity and male mate-guarding in the jewel spider, Gasteracantha minax Thorell (Aranae). Journal of Insect Behaviour, 9: 729-738.
11. Birkhead, T. and Møller, A. (1998) Sperm Competition and Sexual Selection. Academic Press, Amsterdam.