Joro spiders are a wildly invasive species from Asia thought to have arrived on shipping containers in the port of Savannah, Georgia. From there they apparently hitched a ride to north Georgia, where they were first observed in 2014. Drifting on gossamer filaments of silk in an ingenious technique called ballooning, they have now spread into every nook and cranny of north Georgia and northwestern South Carolina — and beyond.
Ballooning in spiders is an extremely effective method of getting from one place to another, and Joros have perfected the art.
Baby Joro spiders, born in the spring, are naturally attuned to wind speed, updraft and humidity. When conditions are just right, they climb to some elevated launch pad and spray drag lines of silk from their little spinnerets. These long drag lines catch the vernal breezes, sending them off into the wild blue yonder. Sometimes it may only be a few dozen yards, but when there is sufficient thermal updraft, they can ascend all the way into the jet stream and drift a hundred miles or more.
Joros are remarkably prolific. I recently took a short four-wheeler trip on our property and encountered no less than a dozen Joro webs in 30 minutes. I was surprised with a face-full of the silk from one web that I did not see coming. I can tell you that it is quite sticky and very effective at catching insects.
Examine a Joro web and you will find numerous insect carcasses neatly wrapped in golden strands of silk. You may also notice a small nondescript spider in some remote corner of the web. Those are the males, just waiting in the wings for the time when they get the call to contribute to the next generation.
The gold-colored silk of Joro webs is only apparent when the sun is at just the right angle; otherwise, they are nearly invisible from a distance.
Female Joro spiders are frightfully big, boldly colored and supported by wickedly long black legs. Frankly, they’re kind of scary looking — somewhat like those giant Halloween spooky spider decorations dangling from front porches this time of year.
While they look scary, Joros are actually pretty timid and will sometimes run and hide if you stand too close to the web. They rarely bite unless threatened, and if they do the wound is not serious and easily remedied in the same way you would treat other insect bites and stings.
The real question about the relatively recent arrival of Joros is whether they will displace our native spiders. Time will tell, but one thing is certain — when they occupy an area, they quickly multiply and fill it to the max.
One fundamental principle of ecology is that when an animal is first introduced into a new habitat, it will rapidly expand beyond the carrying limits of the habitat. The population will then crash, but over time will recover and re-establish itself at a level more in balance with the resources of the habitat.
Meanwhile, don’t get spooked. Joros are now firmly entrenched in the Upcountry of South Carolina and are here to stay.
Dennis Chastain is a Pickens County naturalist, historian and former tour guide. He has been writing feature articles for South Carolina Wildlife magazine and other outdoor publications since 1989.
