Garden Orb Weaving Spiders: Eriophora (Araneidae)
Banded Orb Weaving Spiders: Argiope (Araneidae)
Golden Orb Weaving Spiders: Nephila (Tetragnathidae)
Humped or Silver Orb Weaving Spiders: Leucauge (Tetragnathidae)
Orb weaving spiders are found throughout Australia. Common Garden Orb Weavers are Eriophora biapicata and E. transmarina from eastern and southern Australia. A common Argiope is the St. Andrew's Cross Spider, A. keyserlingi of eastern Australia. Golden Orb Weavers are found in dry open forest and woodlands, coastal sand dune shrubland and mangrove habitats, with Nephila edulis and N. plumipes being the two species found in the Sydney region. The Humped or Silver Orb Weaver, Leucauge, is often found amongst understorey vegetation in moist forest and woodland habitats, including streamside and swampland vegetation.
All orb weaving spiders make suspended, sticky, wheel-shaped orb webs. Webs are placed in openings between trees and shrubs where insects are likely to fly.
The Garden Orb Weavers build large, strong, vertical orb webs. Generally, the spider constructs its web in the evenings and takes it down again at dawn. The spider rests head-down in the centre of the web, waiting for prey. During the day, the spider rests on nearby foliage with its legs drawn under the body. Birds such as honeyeaters are common predators of these spiders. Flying insects such as flies, beetles and bugs (including large prey like cicadas), are common prey. Butterflies and day-active moths are sometimes caught but are partially protected from web entrapment by the presence of scales on their wings - these scales can be shed and this may allow the insect to struggle free of the sticky web.
The Golden Orb Weavers build large, semi-permanent orb webs. The strong silk has a golden sheen. These spiders remain in their webs day and night and gain some protection from bird attack by the presence of a 'barrier network' of threads on one or both sides of the orb web. Sometimes their strong webs manage to trap small birds or bats, and the spider will wrap them and feed upon them. Commoner prey items include flies, beetles, locusts, wood moths and cicadas. Like the St Andrew's Cross Spider, they will vibrate their webs to distract potential predators. Sometimes aggregations of Golden Orb Weavers are found, with a tangled network of overlapping webs. Their webs are often host to the small kleptoparasitic spiders of the genus Argyrodes (often the Quicksilver Spider, Argyrodes antipodeanus) which inhabit the larger spider's web and eat the smaller insects that become trapped on the web, thereby helping keep the web clear of debris.
Humped Orb Weavers build small flimsy, horizontal webs among shrubs and grasses or over water. They remain in their webs during the day and capture flies and other small insects.
The commonly seen Garden Orb Weavers are 2 - 3 cm (female) or 1.5 - 2 cm (male) in body length. Most are stout, reddish-brown or grey spiders with a leaf-shaped pattern on their fat, roughly triangular abdomens, which also have two noticeable humps towards the front. They sometimes have a dorsal stripe which may be white or brown edged with white.
Golden Orb Weavers are large spiders (body 2-4 cm) with silvery-grey to plum coloured bodies and brown-black, often yellow banded legs. The males are tiny (5 mm) and red-brown to brown in colour. The main difference between the common Sydney species, Nephila plumipes and N. edulis (which is commoner in inland regions) is the presence of a 'knob' on the front of the sternum (the heart shaped plate on the underside of the body between the legs) of N. plumipes.
Humped or Silver Orb Weavers are easily recognised by their silvery body, with yellow or green and black markings. They are long-bodied, long-limbed spiders, with a body length of about 1 cm. The abdomen often has rounded 'shoulder' humps that give these spiders their common name.
The female Garden Orb Weaver lays her eggs in late summer to autumn. The eggs are encased in a fluffy silken cocoon and attached to foliage. The lifespan is about twelve months. They mature in summer, mate, lay their eggs, and die in late summer-autumn. Males and females are similar in size. During autumn, the spiderlings disperse by ballooning (floating on the breeze using small silk strands as "balloons"), and build their own tiny orb webs among vegetation.
In the Golden Orb Weaver group, it is common for a number of tiny (6 mm) males to live around the edges of a female's web, waiting for a mating opportunity. After mating, the female Golden Orb Weaver wraps her single egg sac in a mass of golden silk, which is then hidden on foliage away from the web, disguised within a curled leaf or sprig of twigs.
Predators of orb weavers include several bird species and wasps of the family Sphecidae. The wasps land on the web, lure the spider to the perimeter by imitating a struggling insect's vibrations, and then carry the spider away to be paralysed and stored as live food for their young.
Orb weavers are reluctant to bite. Symptoms are usually negligible or mild local pain, numbness and swelling. Occasionally nausea and dizziness can occur after a bite. Humped Orb Weavers have very small fangs and they are timid and reluctant to bite.
Seek medical attention if symptoms persist.
Copyright © Australian Museum, 2003
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