Nephila plumipes
Family Tetragnathidae (Araneomorphae)
Described by P.A. Latreille in 1804.
Nephila: origin uncertain (possible reference (Latin) to Nephele whose daughter fled on a golden ram - an allusion to the golden web of these spiders) plumipes: from Latin: pluma = feather and pes = foot - (perhaps a reference to hair tufts on the legs)
Golden Orb-weaving Spiders are well known for both their large size and the golden sheen of their strong, closely-meshed, aerial webs (40-80 cm diameter) that are suspended amongst shrubs and trees in open forest and woodland. Their long legs have 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 cuticular plate between the spider's leg bases). The orange-brown males are much smaller than the females (dimorphic) - body lengths 4 - 6 mm and 18-25 mm respectively.
Nephila plumipes is found in eastern and northern Australia, especially in coastal areas.
Golden Orb-weavers build semi-permanent webs which they occupy continuously, sitting head-down at the central hub. Their strong orb webs are closely meshed because, unlike other orb weavers, 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 followed by silk wrapping and carrying it back to the hub to feed.
Occupying a web by day has penalties. On hot days Golden Orb-weavers may avoid heat stress by keeping the end of the abdomen pointed at the sun, so presenting a small heating surface. To discourage bird attack Nephila webs have irregular barrier networks spun on one or both sides. As an added deterrent the spider may vigorously shake the web. Food remains and silk-wrapped prey are hung in the barrier web. Small black and silver spiders (Argyrodes spp.) also lurk there, awaiting opportunities to "steal" any tiny insects caught in the web (kleptoparasitism).
Mating occurs in 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 into her genital opening. 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 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, eventually ballooning away.
The flexible strength and beauty of Nephila silk, has resulted in people using 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 unlike silkworms. 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.
Copyright © Australian Museum, 2003
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