Yellow Garden (Argiope aurantia)

Physical description and identification

An adult female yellow garden spider is hard to mistake for anything else. She is large, boldly patterned in black and bright yellow, and she sits openly at the centre of a big vertical web with her legs paired into an X. The species belongs to Argiope, a worldwide genus of conspicuous orb weavers within the orb weaver family, and she shows every hallmark of it: a silvery carapace, a broad egg-shaped abdomen and a taste for sunny, sheltered vegetation.

Adults

• Size: females measure roughly 19–28 mm in body length, with a leg span that can cover a palm. Males are dramatically smaller at about 5–9 mm and are slim, drab and easy to overlook on the edge of the female's web.
• Colour: the abdomen is glossy black with large blocks and bands of yellow and orange, arranged symmetrically either side of a dark median stripe. The carapace is densely clothed in short silvery-white hairs. The legs are black, usually with orange, yellow or reddish bases, and often show pale banding on the front pairs. Seen from below the abdomen is black with two pale lengthwise stripes.
• Eyes: eight small eyes in two rows of four, set on a low carapace. Sight plays almost no part in hunting; the spider reads the web through sensory hairs and slit organs in its legs.
• Distinctive features: three claws on each foot, a fine comb of bristles on the hind legs used to draw out swathing silk, and the habit of resting head-down with the legs held in four close pairs rather than spread evenly.

Eggs and egg sacs

From late summer onwards the female builds one to four egg sacs and hangs them in vegetation close to the web. Each is a rounded, papery brown flask roughly 20–25 mm across, tough enough to shed rain, and holds several hundred to well over a thousand eggs. The eggs hatch inside the sac in autumn, but the spiderlings do not leave: they moult once and overwinter as a dense cluster inside the protective shell.

Spiderlings

The young break out in spring, tiny and dark, and mass briefly on nearby stems before dispersing by ballooning on threads of silk. They spend the summer growing through repeated moults, building progressively larger orbs, and reach maturity from July onwards. Very few survive; egg parasitoids, predators and the hazards of dispersal remove the great majority.

The web

The web is a large vertical orb, commonly 45–60 cm across and occasionally more, anchored to tall plants, fences or eaves in a sunny spot sheltered from wind. Its signature is the stabilimentum: a thick, bright zigzag ribbon of silk running vertically through the hub, which gave the spider its old name of writing spider. Its purpose is still debated. The leading explanations are that it advertises the web to birds so they do not blunder through it, that it reflects ultraviolet light in a way that attracts flying insects, and that it helps conceal the spider's outline. The female rebuilds the central portion of the web most nights, eating the old silk to recycle its protein; our spider web guide explains how the spiral is laid down.

Where the yellow garden spider lives

Argiope aurantia ranges from southern Canada through the contiguous United States into Mexico and Central America, and it has also been recorded in Hawaii. It is common everywhere from the Atlantic seaboard to Texas and California, thinning out only in the driest deserts and at high elevation.

The habitat requirement is simple: tall, stiff vegetation in full sun with enough shelter that the web is not shredded by wind. Field edges, hedgerows, tall flower borders, vegetable gardens, maize and soybean fields, marsh margins, roadside goldenrod and the sunny side of a porch rail all qualify. A female that finds a productive site will usually stay in the same few square metres for the rest of her life, shifting the web only when prey dries up or the plant collapses.

Are yellow garden spiders venomous?

Yes, in the way nearly all spiders are: the yellow garden spider injects venom to paralyse insects caught in its web. It is not dangerous to people. The venom is a fast insect neurotoxin with no medically significant effect on humans or pets, there is no tissue damage of the kind caused by recluse spiders, and no systemic syndrome of the kind caused by widow spiders. Gardeners and farm workers share fields with this species every season without incident.

Can a yellow garden spider bite?

It can, and unlike many orb weavers it is big enough for the fangs to reach skin — but it very rarely does. A female that feels the web shaken will first pump it violently up and down, blurring her outline, and then drop to the ground on a dragline. A bite normally requires the spider to be grabbed, pinned or trapped against the body, for example when clearing vegetation by hand.

The bite itself is usually described as comparable to a bee sting: a sharp local pain with slight redness and swelling that settles within a few hours to a day. Wash the site with soap and water, apply a cold pack, and take a simple analgesic if it aches. See a doctor if the redness spreads over the following days, if pus appears or a fever develops — signs of secondary infection rather than venom — or if you experience hives, breathing difficulty or dizziness, which would suggest an allergic reaction. Avoid home remedies, and keep a photograph of the spider for identification.

Ecological importance and behaviour of the yellow garden spider

This is one of the most valuable predators a garden can host. A single mature female intercepts grasshoppers, crickets, flies, moths, bees, wasps, aphids, leafhoppers and beetles, and she is strong enough to subdue prey heavier than herself, wrapping large insects in a shroud of silk before biting them. In row crops, populations of Argiope measurably reduce numbers of leaf-feeding pests.

Natural predators: birds take adults from the web, mud-dauber and spider wasps paralyse them for their larvae, and lizards, shrews and larger spiders account for others. The egg sacs are heavily attacked by parasitoid wasps and by the larvae of specialist flies, which is one reason so few spiderlings emerge in spring.

Courtship and mating: the mature male builds a small web at the edge of the female's and courts by plucking her radial threads in a set rhythm, advancing when she does not respond aggressively. Copulation is brief and usually fatal to him: his heart stops during the act, and one pedipalp typically breaks off inside the female, forming a plug that reduces the chance of another male mating with her.

Seasonal behaviour: one generation a year. Spiderlings emerge in spring, mature from midsummer, and females reach their maximum size in September and October before dying at the first hard frosts. The egg sacs are what carry the population through winter.

Relationship with people: entirely beneficial and worth leaving alone. Webs built across a footpath can be moved by gently transferring the spider on a stick; she will rebuild within a night.

Similar spiders and how to tell them apart

Quick facts

Did you know?

• The genus name Argiope is Greek, from a mythological naiad whose name combines argos, bright or silvery, with ops, face — a good description of the silvery carapace. The species name aurantia is Latin for orange-coloured.
• Writing spider and zigzag spider both refer to the stabilimentum, and rural folklore in parts of the American South once held that finding your name written in one foretold bad luck.
• The male's death during mating is not an accident of the female's appetite. His heart stops spontaneously, and the broken pedipalp left behind acts as a mating plug — a reproductive strategy, not a predation event.
• Overwintering inside the egg sac lets the spiderlings hatch in autumn without facing the frost, and gives them a head start on insects the following spring.
• Abandoned Argiope egg sacs are readily reused as shelter by other small spiders and by insects.

In summary, the yellow garden spider is a large, dramatic and completely harmless orb weaver whose zigzag signature is one of the sights of late summer. It costs a gardener nothing and repays the space many times over in insects removed.