Cross Orb Weaver (Araneus diadematus)

Physical description and identification

The cross orb weaver is a rounded, heavy-abdomened spider with long banded legs and a group of white marks arranged as a cross on top of the abdomen. Four or five larger dots run down the midline with shorter arms to either side; the exact pattern varies, but some version of the cross is present in every individual. It is the most reliable field mark in the genus.

Adults

• Size: females vary enormously with age and feeding, from 6.5 mm in a young adult to a fat 20 mm (0.8 in) when laden with eggs in October. Males stay slighter at 5.5–13 mm, with a narrower abdomen, longer legs and swollen pedipalps.
• Colour: not diagnostic. Individuals range from pale cream and straw through ginger, brick and foxy orange to deep chocolate or near-grey brown. Darker specimens show a paler folium — a leaf-shaped, scalloped panel — across the abdomen.
• Eyes: eight small eyes in two rows, the side pairs set on low mounds at the edges of the carapace. Vision is poor; the spider judges everything by vibration.
• Other features: the legs are ringed light and dark and bristle with stout spines that pin a struggling fly. The carapace carries a dark central stripe with a paler margin, and short fine hairs give the body a frosted look.

Eggs and egg sac

Mating takes place from late summer into autumn. In September and October the female leaves her web for a sheltered site — under bark, in a crevice, beneath a windowsill or fence rail — and lays several hundred eggs, up to about nine hundred, in a single rounded mass wrapped in a loose pad of pale yellow silk that weathers to dull brown. She does not survive to see them hatch: having laid, she weakens and dies with the first hard frosts.

Spiderlings

The embryos develop inside the sac and the spiderlings overwinter there, emerging in late spring. Newly emerged young are bright yellow with a dark triangular patch and gather in a dense golden ball on a scaffold of silk. Touch it and the ball bursts apart, each spiderling running outward on its own thread, then reassembling minutes later. Within days they disperse for good by ballooning on silk lines, and from then on each one lives alone. There is no maternal care at any stage.

The web

The web is a textbook vertical orb, commonly 20–40 cm in diameter, with around 25–35 radii, a free zone around the hub and a sticky capture spiral. It is strung across gaps in hedges, between fence posts, over gateways, in window frames and among tall grass. Most adults sit head-down at the hub; others build a small tented retreat at the edge and monitor the web through a taut signal thread held in a front leg. The sticky spiral loses its glue within a day or so, so the spider eats the old silk and lays a fresh spiral, often before dawn. For the mechanics, see our guide to spider webs.

Where the cross orb weaver lives

Araneus diadematus is native to Europe and temperate Asia and is one of the most abundant garden spiders anywhere in its range, from Ireland and the United Kingdom east across Scandinavia, central Europe and Russia. It arrived in North America with European settlement and is now thoroughly established there, from New England and the mid-Atlantic to the Great Lakes and, most densely of all, through the Pacific Northwest, British Columbia and northern California. Populations are heaviest in cool, damp maritime climates.

Habitat is anywhere with structure to anchor a web and flying insects to fill it: hedgerows, woodland edges, reed beds, heath, gardens, allotments and the outsides of buildings. The sheltered corner of a porch, a greenhouse frame or a lit window is prime real estate. It is not an indoor spider, so a cross orb weaver on a living-room wall has wandered in by mistake.

Are cross orb weaver spiders venomous?

Yes, like effectively all spiders, and the venom is used to quiet insect prey. It carries no medical significance for humans: no tissue damage, no systemic illness, no lasting effect, and no antivenom has ever been needed. The old claim that its venom is unusually potent because it "liquefies" a victim's insides describes something every spider does — digestion happens outside the body, with enzymes pumped into the prey and the fluid sucked back out. Ordinary spider biology, not exceptional toxicity.

Can cross orb weaver spiders bite?

They can, but it takes real provocation. The instinct on being disturbed is to bounce the web until it blurs, then drop to the ground on a dragline and freeze. Bites happen almost exclusively when a spider is squeezed — pressed inside a glove, rolled against skin while gardening, or gripped. The fangs of even a large female barely break skin on a hand, and the sensation is usually compared to a nettle sting: brief sharp pain, a small red mark, occasionally some itching, gone within hours.

Wash the site with soap and water and apply a cold pack if it stings; no other treatment is needed. Seek medical advice only if the area becomes hot, spreading and increasingly painful over the following days, which points to a skin infection rather than venom, or if you have signs of an allergic reaction such as hives away from the bite or difficulty breathing.

Ecological importance and behaviour of the cross orb weaver

An adult female running a 40 cm web takes hundreds of flying insects over a season — craneflies, midges, mosquitoes, hoverflies, blowflies, moths, aphids and winged ants. Prey is rushed, bitten and wrapped in broad bands of silk, then eaten at the hub or stored for later. The spider is discriminating: a wasp or bee that could sting is often cut free rather than risked.

Natural predators: tits, wrens and other small birds pick spiders off webs, and spider-hunting wasps paralyse them as larval food. Parasitoid ichneumon wasps lay on the abdomen and the larva feeds externally, sometimes manipulating the host into spinning an abnormal cocoon web before killing it. Shrews, frogs and larger spiders take the rest.

Courtship and mating: the male stops web-building at maturity and goes looking for females. He approaches the edge of an orb, plucks the silk in a deliberate rhythm to announce that he is not food, and attaches a mating thread he can retreat along. In this species males frequently die spontaneously during copulation — the heart stops while the palp is still engaged — and the female then consumes the body. Less an attack by the female than a male investing everything in one encounter.

Seasonal pattern: spiderlings emerge in late spring, grow through the summer, and the species becomes conspicuous from August to October when the females reach full size and webs appear everywhere at once. Adults die off with the first sustained frosts and the population overwinters as eggs.

Relationship with people: wholly beneficial and worth leaving alone. Remove a web's anchor points rather than the spider and she will relocate within a night.

Similar spiders and how to tell them apart

Quick facts

Did you know?

• The white cross is a waste product: clusters of cells packed with crystalline guanine, a nitrogen compound stored just under the cuticle, where it happens to show as brilliant white.
• Two cross orb weavers, Arabella and Anita, flew aboard NASA's Skylab 3 mission in 1973 to test whether a spider could spin in weightlessness. Their first attempts were ragged, but both went on to build recognisable orbs.
• Carl Clerck named the species in 1757, in the work that is the starting point for all spider nomenclature — making Araneus diadematus one of the oldest valid spider names in existence.
• A female's weight can triple between midsummer and the moment she lays; much of the bulk people photograph in October is egg mass, not spider.

In summary, the cross orb weaver is a harmless, extraordinarily common autumn spider with the clearest field mark in the family. Find the white cross on a bulbous abdomen at the centre of a fresh wheel of silk and the identification is finished. More of the family on our orb weaver hub, and compare the yellow garden spider.