Every late summer the Joro spiders come into their own. They’re from East Asia, were first found in the U.S. near Athens, Georgia in 2014, and have spread through the Upstate since. By September the females are full-sized, banded yellow and blue-black, with webs strung between trees, eaves and porch lights.
The first time you walk face-first into one, it’s hard to feel neighbourly about it. A full-grown female can span the width of your palm with her legs out, and the webs glint gold in the morning light. But the more I’ve learned about them, the more they’ve become one more part of the fall garden, like the goldenrod and the first cool mornings, rather than something to wage war on.
Not dangerous
Clemson Extension says the venom isn’t medically relevant and isn’t known to harm people or pets. Bites are rare. The spiders are docile and would rather drop or flee than bite, and when a bite does happen it’s about like a mosquito bite: a small, itchy red welt, gone in a day or two. They’re also unlikely to come indoors.
Where they came from, and what we don’t know yet
Joros most likely arrived riding on shipping containers. Since then they’ve spread across Georgia and into South Carolina, North Carolina and Tennessee. Young spiders travel by “ballooning,” letting out a thread of silk and riding the wind, sometimes for many miles. A 2022 University of Georgia study found they handle cold far better than their close relative, the golden silk spider, with a higher heart rate and metabolism in chilly weather, and concluded they could likely survive through most of the Eastern Seaboard.
What they do to local ecosystems is still being studied. They eat a lot of insects, including pests like stink bugs. Whether they crowd out native orb-weavers is an open question. That’s one reason the University of Georgia runs Joro Watch, a citizen-science project where anyone can report a sighting with a photo. Every report helps researchers map the spread, and it turns an uneasy feeling about a new neighbour into something useful.
The webs
The orb itself is usually around two feet across, but the anchor lines can stretch several feet on every side, which is how you end up wearing one. I treat it as seasonal maintenance, like raking.
- Knock down webs across paths and doorways with a cobweb brush or a broom.
- Move the spider instead of killing it. Carry it on the brush to the edge of the woods, away from where people walk. Clemson notes that relocating them well away from where they were found can keep them from coming back.
- Leave the ones that aren’t in anybody’s way. A web strung between two shrubs at the edge of the yard is doing pest control for free.
- Wave a stick ahead of you on paths through the woods in September and October. Old advice for orb-weavers of every kind.
- The season ends on its own. Adults die with the first hard freeze, after laying eggs in late fall. The next generation hatches in spring.
Why not spray
Clemson’s factsheet notes that any registered acaricide will kill them. I don’t use one, for the same reason I don’t spray the garden for much of anything. A spray strong enough to kill a large spider in an open web drifts onto everything else: the pollinators working the fall asters, the other spiders, the lacewings and ground beetles that keep the garden in balance. The broom works, costs nothing and doesn’t poison anything. And the problem is gone with the first freeze anyway.
Further reading
- Jorō spider, Clemson HGIC factsheet 2517. Identification, safety and management for South Carolina.
- Joro Watch, University of Georgia. Report a sighting and see the latest spread maps.
- Large, parachuting spiders could soon invade the East Coast, Smithsonian Magazine, 2022. On the UGA cold-tolerance study.
- iNaturalist. Photograph and identify what’s living in your yard, and share it with researchers.
- Xerces Society. Science-based conservation of insects and other invertebrates, including how to garden without pesticides.