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Nephila plumipes (Family Tetragnathidae)

Golden Orb-weaving Spider

Distribution:

Nephila plumipes is found in eastern and northern Australia, especially in coastal areas. Spectacular congregations may be seen in mangroves habitats. (VIC, NSW, QLD)

Features:

Golden Orb-weaving Spiders are well known for both their large size and the golden sheen of their strong, closely-meshed, aerial webs (40 to 80 cm diameter) that are suspended between amongst shrubs and trees in open forest and woodland. well above the ground. Their long legs bear yellow bands, the carapace has a covering of silvery hairs and the light silvery-grey abdomen becomes yellow-brown behind. Nephila plumipes has a characteristic tubercle near the front of the sternum (the plate between the spider's leg bases). The orange-brown males are much smaller than the females (the sexes differ in form), with body lengths of 4 to 6 mm and 18 to 25 mm respectively.

Ecology/Way of Life:

Golden Orb-weavers build semi-permanent webs which they occupy continuously, sitting head-down at the central hub. Unlike other orb-weavers, their strong orb webs are closely meshed because they leave both the scaffolding and stick silk spirals in place as well as doubling each radial line. Nephila webs are sometimes very numerous, forming spectacular congregations in habitats such as mangrove stands. Much of their food is caught by day, while at night the spiders repair their webs. Their insect prey includes beetles, bees, flies, leafhoppers, wasps and cicadas. They subdue their prey by first biting it, then wrap it in silk and carry it back to the hub to feed.

Occupying a web by day has penalties. On hot days, Golden Orb-weavers will may avoid excessive heat stress by keeping the end of the abdomen pointed at the sun, so presenting a small heating surface. To discourage bird attack, Nephila these spiders spin irregular barrier networks on one or both sides of the web. As an added deterrent the spider may also vigorously shake the web. Food remains and silk-wrapped prey are hung in the barrier web, where small black and silver spiders (Argyrodes spp.) lurk, awaiting opportunities to "steal" any tiny insects caught in the web (kleptoparasitism).

Mating occurs in late summer-autumn and is closely associated with feeding. Often several small males sit in the upper outskirts of the web. If the female begins feeding, an approaching male will advance slowly on the opposite side of the web, occasionally web-plucking, to make sure that the female is fully preoccupied. His small size also disguises his approach. He then slips onto the female's side of the web, climbs under her abdomen, and inserts his mating organs alternately into the female'sher genital opening. Unreceptive females may attack advancing males and cannibalise them. Male size varies and this may affect mating success; the smaller males may approach the female and mate virtually unnoticed but they are also more likely to be chased away before mating by the larger males. A female spins one yellow silk egg sac per season, concealing it among foliage, where its yellowish silk may "weather" to a greenish tinge; each egg sac may contain from 300 to 1000 eggs. Spiderlings hatch in about 2 weeks and emerge after about a month; they overwinter in the egg sacs before emerging and dispersing by ballooning in spring.

Interaction with Humans/Threats:

The flexible strength and beauty of Nephila silk has attracted people to use it for many purposes, ranging from making fishing nets to weaving ceremonial garments. For weaving purposes, the difficulty has always been harvesting sufficient silk from such uncooperative, solitary and predatory animals - very different to silkworms cocoons.! Biotechnology is solving this by identifying, isolating and transferring spider genes responsible for silk protein production into organisms such as bacteria, plants and even the secretory cells of goat's udders, with the aim of producing harvestable silk in commercial quantities. Potential uses range from medical sutures and artificial tendons to suspension bridge cables and composite materials for the space industry.

Other Comments:

Described by L. Koch in 1839; the genus name comes from the Latin nere = to spin, and -phila = attracted to; the species name is from the Latin: pluma = feather and pes = foot, perhaps a reference to the hair tufts on the legs.

Further Reading:

Austin, A.D, and Anderson D.T. (1978). Reproduction and development of the spider Nephila edulis (Koch) (Araneidae: Araneae). Australian Journal of Zoology 26: 501-518.

Beattie, A. and Ehrlich, P.R. (2000). Wild Solutions: How biodiversity is money in the bank. Melbourne University Press.

Elgar, M. and Fahey, B. (1966). Sexual cannabilism, competition and size dimorphism in the orb-weaving spider Nephila plumipes Latreille (Araneae: Araneoidea). Behavioural Ecology 7: 195-198.

Herberstein, M.E. and Elgar, M.A. (1994). Foraging strategies of Eriophora transmarina and Nephila plumipes (Araneae: Araneoidea): nocturnal and diurnal orb-weaving spiders. Australian Journal of Ecology 19: 451-457.

McKeown, K. (1963). Australian Spiders. Angus and Robertson, Sydney.

Topics: Spider webs Sexual cannabilism Silk Prey capture Kleptoparasitism

Acknowledgments:

Text & map by Mike Gray; photographs by Mike Gray, courtesy of the Australian Museum.

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