Feather-legged (Uloborus walckenaerius)

Physical description and identification

One point of classification first, because it changes everything else on this page. The feather-legged spider is not a crevice weaver. It belongs to the family Uloboridae, the cribellate orb weavers, and not to Filistatidae, the family of the southern house spider and the rest of the crevice weavers in this section of the site. The two groups share only one feature — cribellate silk — and Uloboridae is separated from every other spider family by something far more unusual: its members have no venom glands at all.

Adults

• Size: small. The body is roughly 3–6 mm long, females larger and heavier-bodied than males, and the whole animal with legs extended still sits comfortably on a fingernail.
• Color: cryptic pale grey-brown to buff, mottled and often marked with darker longitudinal streaks and paler bands on the legs. The effect at rest is a fragment of dried plant material rather than a spider.
• Distinctive features: tufts of long, plumose setae on the tibiae of the first pair of legs — the feathers of the name. At rest the spider stretches those front legs straight forward and the hind legs back, flattening its outline into a short twig.
• Cribellum and calamistrum: in place of the glue-producing glands of a garden orb weaver it has a cribellum, a plate of thousands of tiny spigots in front of the spinnerets, and a calamistrum, a comb of bristles on the fourth legs that teases the output into a woolly hackled band.

Eggs

The female builds an elongated, angular egg sac, often with projecting points, and fastens it near the web or holds it beneath her. The sac is camouflaged to match dead plant fragments and is normally the last thing an observer notices about an occupied web.

Spiderlings

Spiderlings emerge resembling miniature adults in colour, though they are paler and far smaller. They disperse quickly, some on short silk lines, and build their own tiny orbs within a few molts. Juveniles often build simplified webs with fewer spiral turns before working up to the full adult structure.

The web

This is a true orb, but an unusual one. It is built horizontally or at a shallow angle rather than vertically, slung low among heather, grass stems or low shrubs, and the spider hangs beneath the hub. The capture spiral is not coated in glue; it is cribellate silk, dry and fuzzy, which holds an insect by snagging its bristles and claws in a mat of nanofibres. Many webs also carry a stabilimentum, a band or cross of dense white silk at the hub whose function is still debated — variously interpreted as camouflage, as a web-strengthening feature or as a visual signal that stops birds flying through. See our guide to spider webs for how cribellate and glue-coated orbs compare.

Where the feather-legged spider lives

Uloborus walckenaerius is a Palaearctic species, not a global one as some summaries claim. It occurs across much of Europe — commonest around the Mediterranean, including Spain, Portugal, France, Italy and the Balkans — and its range continues east through Russia and Central Asia to China. In the United Kingdom it reaches the northern edge of its distribution and is genuinely rare, restricted to a handful of dry lowland heaths in southern England, where it is treated as a species of conservation concern.

The habitat is specific: warm, dry, open ground with low woody vegetation. Heather, gorse, dwarf shrubs, calcareous grassland and sunny scrub edges all qualify, and the web is generally strung within 10–50 cm of the ground between stems. It is not a house or garden-centre spider; that reputation belongs to its relative Uloborus plumipes, a tropical species that thrives in heated greenhouses across Europe and is often mislabelled with this one's name.

Are feather-legged spiders venomous?

No — and this is not the usual hedged answer given for harmless spiders. The feather-legged spider does not merely have weak venom; it has no venom glands. Uloboridae is the only spider family known to have lost them completely, so there is no venom to inject, no matter how the spider is handled. It cannot envenomate a person, a pet or an insect. Its chelicerae are small and its fangs are used to hold and manipulate prey that has already been immobilised with silk, not to subdue it.

Can feather-legged spiders bite?

In practice, no. The spider is 3–6 mm long, extremely timid, and its response to a hand is to drop from the web on a dragline or to stretch out and pretend to be a twig. Its fangs are not built to break human skin, and even if they did there would be nothing to deliver. No bite from this species requires treatment of any kind, and no medical literature records one.

Ecological importance and behavior of the feather-legged spider

The feather-legged spider is an ambush predator that never leaves its web voluntarily. It hangs under the hub with the front legs extended along the radii, detects a strike by vibration, and moves straight to wrapping — there is no rush-and-bite phase, because there is nothing to bite with to any effect. Prey is small and soft: flies, midges, aphids, small moths, leafhoppers and other low-flying insects of open heath.

Natural predators: insectivorous birds, wasps that provision nests with spiders, predatory bugs and larger spiders all take uloborids. With no venom and almost no speed, the spider's defence is entirely camouflage and stillness, backed by dropping from the web when that fails.

Prey-predator dynamics: horizontal orbs close to the ground intercept a different set of insects from the vertical webs of orb weavers higher up, so on a heath the two groups partition the airspace rather than compete. A good season produces dense local populations that take a meaningful share of the small flies emerging from damp hollows.

Seasonal behavior: adults appear in late spring and summer, with mating and egg-laying through the warm months and juveniles overwintering in low vegetation. Most individuals complete their lives within about a year. Males are shorter-lived than females and stop building webs once mature.

Relationship with humans: entirely benign. The species is of interest chiefly to conservation ecologists, because dry lowland heath is a shrinking habitat across north-west Europe, and a spider tied that tightly to it is a useful indicator of heathland quality.

Similar spiders and how to tell them apart

Quick facts

Did you know?

• Uloboridae is the only family in the entire order Araneae known to have lost its venom glands. Every other spider, including the harmless ones, retains them.
• Losing venom cost the family nothing in efficiency: uloborids are among the most extreme silk-wrappers known, and a single small fly can be bound in hundreds of metres of thread.
• Cribellate silk is the ancient form of spider capture thread. These spiders build an orb with it, which is why they matter so much to arguments about how, and how many times, the orb web evolved.
• The species was named in 1806 by Pierre André Latreille, and honours the French naturalist Charles Athanase Walckenaer, one of the first people to attempt a global catalogue of spiders.
• Its relative Uloborus plumipes has become a fixture of European garden centres, where the warm, insect-rich air of a glasshouse suits it perfectly.

In summary, the feather-legged spider is a tiny, cryptic heathland orb weaver that has thrown away the one weapon people associate with spiders. It has no venom glands, cannot harm anything larger than a midge, and solves the same problem with silk — which makes it one of the most quietly remarkable spiders in Europe.