Cat-Faced (Araneus gemmoides)

Physical description and identification

The cat-faced spider is one of the easiest orb weavers in western North America to name on sight, and the reason is the shape of its abdomen rather than its colour. Two blunt, horn-like tubercles sit on the front shoulders; beneath them are two dark dimples where muscles anchor internally, and below those a pale, roughly triangular patch. Together they read as ears, eyes and a muzzle. Everything else is a textbook Araneus: a heavy, pear-shaped body, short thick legs and very poor eyesight. Compare it with the rest of the genus on our Araneus page, or browse the whole orb weaver family.

Adults

• Size: mature females measure about 13–25 mm in body length, and a well-fed female in October is a genuinely bulky spider. Males are far smaller at roughly 5–8 mm, with proportionally longer legs.
• Colour: extraordinarily variable — pale straw, cream, ochre, orange, rust or deep chocolate brown, and pale and dark forms can emerge from a single egg sac. Colour is therefore useless as a species character; the body outline identifies the spider. Most individuals show a scalloped, dark-edged pattern (the folium) down the back.
• Eyes: eight eyes in two rows of four, the four middle eyes grouped into a small raised square. Like all orb weavers it sees little more than light and movement, and its world is built from vibration rather than images.
• Distinctive features: short legs faintly banded light and dark, a dense covering of fine hairs, and three claws on each foot — the hooked third claw lets an orb weaver walk its own silk. Mature males have swollen, club-shaped pedipalps and a flat abdomen with no humps.

Eggs and egg sac

Mating happens in late summer. The female then produces one or two egg sacs of several hundred eggs each, wraps them in loose, papery silk and fastens the package to a sheltered vertical surface — under an eave, behind siding, inside a window frame. She guards it until the first hard frost kills her. The eggs hatch within a few weeks, but the spiderlings stay inside the sac and overwinter there.

Spiderlings

The young emerge in spring, pale and barely a millimetre across, and cluster in a tight shimmering ball before dispersing. Most leave by ballooning, climbing high, releasing a strand of silk and letting the breeze carry them off. They build tiny orbs, grow through a series of moults, and mature in August or September. Only a small fraction reach adulthood, mostly through predation, starvation and failed dispersal rather than the sibling cannibalism the species is often credited with.

The web

The web is a classic vertical orb, typically 30–60 cm across, with a dense hub, a free zone and an outer spiral of sticky capture silk. It is strung in sheltered gaps with a clear flight path: between porch posts, across a doorway corner, under shed eaves. The spider usually takes it down and rebuilds overnight, eating the old silk to recycle its protein. By day it sits head-down at the hub or retreats into a curled leaf at the end of a taut signal thread. Our spider web guide explains how that spiral is engineered.

Where the cat-faced spider lives

Araneus gemmoides is a western and central North American species. It is common from British Columbia and Alberta south through Washington, Oregon, Idaho, Montana, Colorado, Utah, Nevada, Arizona and New Mexico, and east across the Great Plains to the Dakotas, Nebraska and Kansas. Records thin out east of the Mississippi, where its relatives take over. It reaches high elevations in the Rockies and tolerates cold, dry summers well.

Its preferred habitat is any sheltered vertical gap near a reliable supply of flying insects: sagebrush and riparian scrub, rock faces, the mouths of rodent burrows and, above all, human structures such as house eaves, porch ceilings, window frames, barns and fence lines. A porch light is close to an ideal hunting position, and the same corner is often occupied year after year.

Are cat-faced spiders venomous?

Yes — like almost all spiders, the cat-faced spider has venom glands and uses venom to subdue insects. It is not, however, dangerous to people. The venom of Araneus orb weavers is a fast-acting insect toxin with no medically significant effect on humans or pets, and there are no confirmed cases of serious illness from a cat-faced spider bite. It is unrelated to the recluse spiders and the widow spiders, which are the only two North American groups of real medical concern.

Can a cat-faced spider bite?

It can, but almost never does. A disturbed cat-faced spider drops out of the web on a dragline or bounces the web violently to blur its outline; biting is a last resort when the spider is squeezed against skin — if a gardener closes a hand around one, or a wandering male is pressed inside clothing. The fangs are short and frequently fail to break the skin. When they do, the result is a brief pinch and perhaps a small red mark or some itching that fades within a day.

First aid is the same as for any minor spider bite: wash with soap and water, apply a cold pack, and leave it alone. Seek medical advice if the area develops spreading redness, pus or fever, which points to a skin infection rather than venom, or if there is any sign of a generalised allergic reaction. Do not apply home remedies, and keep the spider or a photograph if you safely can — accurate identification prevents a great deal of unnecessary worry.

Ecological importance and behaviour of the cat-faced spider

A cat-faced spider is a passive, energy-efficient hunter. It invests a large amount of protein in a web every night and then waits, legs resting on the signal lines, for the vibration that means a moth, midge, mosquito, fly, beetle or wasp has hit the sticky spiral. It rushes out, wraps the prey in swathing silk and bites it. A single female beside a porch light can remove hundreds of night-flying insects in a season.

Natural predators: mud-dauber wasps — the black and yellow mud dauber Sceliphron caementarium among them — are important enemies, paralysing spiders and sealing them into mud cells as food for their larvae. Birds, lizards, mantises and larger spiders take their share, and parasitoid wasps attach larvae that feed on the spider from outside.

Prey–predator dynamics: because the webs sit at head height in flight corridors, this species intercepts insects that ground-level hunters never see. Newly emerged spiderlings will occasionally eat a sibling when crowded, but the idea that most young are eaten by their siblings is folklore.

Seasonal behaviour: the species runs one generation a year. Spiderlings appear in spring, grow through repeated moults, mature in late August and September, and the females swell with eggs through October. Males stop building webs once mature and wander in search of females, plucking a courtship rhythm on the outer threads. Adults die with the first hard frosts; only the egg sac survives winter.

Relationship with people: a beneficial, non-aggressive neighbour that needs no control. If a web blocks a doorway, brushing it down in the evening usually persuades the spider to rebuild a metre away.

Similar spiders and how to tell them apart

Quick facts

Did you know?

• The cat face is not a marking at all. The ears are hardened abdominal tubercles, the eyes are muscle attachment dimples visible through the cuticle, and the muzzle is part of the pale folium — the spider's real eyes are on the carapace, far below.
• The name jewel spider is shared with the very different Australian Austracantha minax, a spiny orb weaver, so the common name alone can send you to the wrong continent.
• An orb weaver digests its old web and reuses the protein, which is why a fresh web can appear each night without the spider needing to eat first.
• Colour in this species is so variable that early arachnologists described pale and dark forms as separate species before rearing them from one egg sac settled the question.

In summary, the cat-faced spider is a harmless, short-lived and remarkably useful autumn visitor. Learn the two shoulder horns and you can identify it instantly, ignore the folklore about dangerous bites and sibling-eating broods, and let it work the porch light for the few weeks it has.