Giant Wood Spider (Nephila pilipes)

Physical description and identification

Almost nothing else in a Southeast Asian forest looks like an adult female Nephila pilipes. She hangs head-down in a wide yellow orb, her body longer than a thumbnail and her banded black-and-yellow legs stretched far beyond it. She is the type species of the genus Nephila and the largest golden orb-weaver, a group that sits inside the orb-weaver family as the subfamily Nephilinae.

Adults

• Size: the sexes differ enormously. Female body length runs from roughly 30 mm to 50 mm, with a leg span that regularly reaches 12–20 cm. Males mature at only 5–6 mm and weigh a tiny fraction of what an adult female weighs.
• Colour: the female's carapace is dark and covered in fine silvery-white hairs. Her long abdomen is mostly black or deep olive with paired yellow to cream blotches along the sides, and the underside carries a bold black pattern with red or yellow markings. The legs are black with vivid yellow or orange bands at the joints. Males are plain reddish brown with no banding.
• Eyes: eight small eyes in two rows of four, the side pairs set close together on low tubercles. None are enlarged; this spider works almost entirely by touch and vibration.
• Distinctive features: the abdomen is elongated and cylindrical rather than round, which separates Nephila from almost every other large orb-weaver. Mature females lose the juvenile leg hair, leaving a smooth, glossy, obviously banded leg.

Eggs and egg sac

The egg sac is not hung in the web. The female comes down to the ground near her supporting tree, digs a shallow pit, deposits a silk-wrapped mass of several hundred to a couple of thousand eggs, then covers it with soil, leaf litter and camouflaging silk. Burying the sac hides it from ants and parasitoid wasps. Females usually lay once at the end of their lives and die soon afterwards.

Spiderlings

Hatchlings are pale and stay bunched together briefly before dispersing on silk lines. Juveniles of both sexes carry conspicuous brushes of dark hair on the first, second and fourth pairs of legs; the third pair lacks them. Those brushes are lost as a female matures, so a hairy-legged juvenile and a smooth-legged adult can look like two different spiders. Females pass through many more molts than males before maturing, which is the real reason for the size gap — contrary to a widespread claim, neither sex keeps molting once adult.

The web

The orb is a fine-meshed golden wheel commonly 50 cm to 1 m across, hung from bridge lines that may run several metres between trees and often tilted slightly from vertical. In front of and behind it hang loose curtains of tangled barrier silk that stop birds flying through and knock insects into the trap. The silk is genuinely yellow, coloured by pigments the spider adds as she spins, and the frame lines are strong enough to be felt as a tug across the face. Unlike most orb webs, this one is semi-permanent: the female repairs sections rather than rebuilding nightly, so a single web may stay up for weeks or even months — not for years, as is sometimes claimed, since the spider lives only about a year.

Where the giant wood spider lives

Nephila pilipes is an Old World species with one of the widest ranges of any large orb-weaver. It occurs from India, Nepal, Sri Lanka and Myanmar eastwards through Thailand, Laos, Cambodia, Vietnam, southern China, Taiwan and southern Japan, south through Malaysia, Singapore, the Philippines and Indonesia to Papua New Guinea and the tropical north and east coasts of Australia.

Across that range the habitat requirement is consistent: a warm, humid, lightly wooded place with gaps wide enough to bridge. Primary and secondary rainforest, forest edges, clearings, river margins, mangroves, plantations, wasteland scrub and large gardens all suit it. Webs go up across footpaths, between trees, along fence lines and under the eaves of buildings at the forest edge, usually one to four metres above the ground. It is a lowland spider, scarce in cool uplands and absent from open desert.

Are giant wood spiders venomous?

Yes, in the sense that nearly every spider is venomous: Nephila pilipes uses venom to subdue the large flying insects that hit a web this size. The venom is not medically significant to humans or pets: it is tuned to insect nervous systems, delivered in small amounts, and has never been associated with tissue damage, systemic illness or a death. There is no antivenom because none is needed.

Can giant wood spiders bite?

They can, but bites are genuinely rare. A female's first response to disturbance is to shake the web violently, then drop out of it on a dragline; she bites only when pinched or pressed against skin, which usually means somebody has walked into the web and grabbed at it. Her fangs are large enough to break skin easily, so the puncture itself is felt.

A bite produces sharp but short-lived pain often compared to a bee sting, with local redness and mild swelling that fade within a day. Blistering, numbness and nausea are not expected. Wash the site with soap and water, apply a cold pack and take a simple painkiller if needed. Seek medical advice if pain worsens after the first day, if redness spreads, or if there is breathing difficulty or faintness — that would be an allergic reaction of the person rather than an effect of the venom. Do not cut, suck or burn the bite, and keep a photograph of the spider if you can.

Ecological importance and behavior of the giant wood spider

A giant wood spider's web is a standing trap that works day and night. The female stays at the hub, reading tension in the radial lines to locate anything that lands. Large or dangerous prey is wrapped in silk before it is bitten; small items are bitten first. The diet is overwhelmingly flying insects — flies, bees, wasps, moths, beetles, grasshoppers and large cicadas — and one web removes hundreds of them in a season.

The exceptional catches: because the frame silk is so tough, small birds and bats are occasionally found entangled. Such cases are documented but unusual, and the spider often cannot subdue a struggling vertebrate at all.

Males and freeloaders: mature males stop building webs and live as tenants at the edge of a female's orb, approaching her while she is feeding or molting to reduce the risk of being eaten. Kleptoparasitic dewdrop spiders (Argyrodes) live in the barrier silk and steal wrapped prey; a large female may support a dozen uninvited guests.

Natural predators: birds, lizards, monkeys and spider-hunting wasps take adults, ants and parasitoids raid buried egg sacs, and in parts of Asia predatory damselflies pluck small spiders out of orb webs. Juveniles are far more vulnerable than adult females, whose size and bold colouring deter many attackers.

Relationship with humans: almost entirely positive. The species removes huge numbers of flying insects and never colonises the inside of a house. In Bình Thuận Province in Vietnam the Raglai people roast and eat the spiders. If a web blocks a doorway, lift the female onto a stick and move her to a nearby shrub instead of killing her.

Similar spiders and how to tell them apart

Quick facts

Did you know?

• Nephila pilipes is the type species of the genus — the reference point against which every other Nephila is compared.
• Several subspecies have been named, among them N. p. hasselti from Java and N. p. lauterbachi from New Guinea, though their status is debated.
• Juveniles build a line of insect husks and plant debris across the hub. Experiments show these decorations lower the chance of a wasp attack by breaking up the spider's outline.
• The bright yellow-and-black colouring is not an accident: field experiments indicate it works as a visual lure for insects while also deterring larger animals.
• Golden orb silk absorbs more energy before breaking than steel of the same weight, which is why it has been studied for sutures and nerve-repair scaffolds — and why Pacific islanders once stretched these webs over bent frames to make fishing nets.

In summary, the giant wood spider is spectacular but completely harmless. Learn the cylindrical black-and-yellow abdomen, the banded black legs and the semi-permanent golden orb, and you will recognise it for what it is: a superb insect trap with no interest in you.