Are Joro Spiders Bad? Are they an Invasive Species?

Written by Cindy Rasmussen
Published: March 10, 2022
© Kelly vanDellen/Shutterstock.com
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Killer bees are bad. Murder hornets are bad too, but are Joro spiders bad? They may be giant parachuting spiders but Joro spiders are not harmful. They are not native to the United States, they are from Japan. The first Joro spiders were found in Georgia in 2014 and have spread throughout Georgia and into South Carolina. That doesn’t necessarily make them “invasive”. Let’s find out if these spiders are bad and considered an invasive species.

What are Joro spiders?

close up of a Joro spider
These giant parachuting spiders are very colorful and weave large golden webs.

©iStock.com/David Hansche

Joro spiders are large colorful spiders that weave golden webs. They can get to be 3-inches wide with their long skinny legs stretched out. The body of the Joro spider is black and yellow with red markings mixed in. They have distinctive blue and yellow-banded legs and can be found in giant golden webs (some as big as 10 feet across). Part of the Orb-weaver family, the webs are spherical versus the more common funnel-web (tighter woven in the middle, then gradually getting further apart as you get closer to the outside of the circle). They make their webs in gardens, next to sheds and behind garages so they are a very visible spider.

How did they get here?

Most invasive species are brought into the country accidentally by humans. The TSA bans passengers from bringing in fruit or vegetables from areas like Hawaii, Puerto Rico, and the U.S. Virgin Islands “due to the risk of spreading invasive plant pests”.

Africanized Honey Bees (aka Killer Bees) migrated north to the US from an original group of 26 swarms that were accidentally released in Brazil in 1957. Wait, Brazil is not in Africa? Correct, the bees from Africa were brought to Brazil on purpose by bee experts in 1956 to start a cross-breeding program. They were hoping to create bees that would increase honey production.

It is unknown how Joro spiders got here. The most common belief is that they came over from Japan or other Asia countries in shipping containers.  

What is an invasive species?

First, we need to define an invasive species. The term “invasive” is commonly used to define a animals, plant, insect etc. that wasn’t here before. They are new to the environment or area. But the technical definition according to the USDA is that they have to be new to the environment and harmful. There is even an Executive Order signed in 1999 that defines an invasive species as:

  • “non-native (or alien) to the ecosystem under consideration and,
  • whose introduction causes or is likely to cause economic or environmental harm or harm to human health.”

So to determine if a species is an invasive species you would need to ask the following four questions:

            1. Are Joro spiders non-native?

            2. Are Joro spiders affecting the economy in any negative way?

            3. Do Joro spiders wreck the environment (plants, animals, other spiders etc.)?

            4. Are Joro spiders harmful to humans?

Joro spider in web
Joro spiders are from Japan and other East Asian countries. They were first identified in the US in Georgia in 2014.

©iStock.com/Jef Wodniack

1. Are Joro spiders non-native?

Yes! We know that before 2014 there were not Joro spiders in the United States. They are native to Japan and a few other East Asian countries. So, yes they are non-native to the United States. A recent study by the University of Georgia states that the Joro spider “could colonize the entire East Coast”. The study reveals that the Joro spider is more resilient to the cold than the golden silk spider implying that the Joro may be able to survive better in the cooler northern states along the coast.

2. Are joro spiders affecting the economy in any negative way?

No! Not yet at least. We are still learning about the Joro spider, but it has been in Georgia since 2014 with its population growing fast without any recorded negative impacts on the economy. For example, the Asian Giant Hornet (nicknamed “Murder Hornets”) were found in Washington state in December 2019. The biggest problem with Murder Hornets is that they can wipe out an entire hive of honeybees in an hour. Imagine the impact that would have on the honey industry if they were to spread throughout the US. Not just the honey industry but many crops, like fruits and vegetables depend on pollinators like honeybees. So you can see the ripple effect.

3. Do Joro spiders wreck the environment (plants, animals, other spiders etc.)?

No! So far the Joro spider does not seem to be negatively affecting other plants, animals, or fellow spiders. An example of an animal that is invasive because of its effect on the environment is the feral pig. These can be located in every county in Georgia and are very destructive. A herd of feral pigs can eat and trample crops, kill off livestock like calves and lambs and they are also harmful to humans by carrying diseases. They are the poster pig for invasive species.

One Georgia resident commented how you can get covered by spider webs just from mowing your lawn which could be considered annoying but not an environmental hazard.

4. Are Joro spiders harmful to humans?

No! Joro spiders are not harmful to humans. They prefer to stay away from humans and are not aggressive. Joro spiders are venomous but their venom is not toxic to humans (unless someone is allergic). Their bites are extremely rare because their fangs are not large enough to puncture human skin. They are not harmful to pets either for the same reason.

Are Joro spiders bad?

Joro spiders are not bad. They are not harmful to our environment, other animals or plants and they are not dangerous to humans. In fact, they can be good!

Are Joro spiders good?

Joro Spider in Web
Joro spiders eat mosquitoes! Their webs are excellent at catching these pesky bugs.

©Surapong Kaewsa-ad/Shutterstock.com

Yes! There are actually some benefits that these colorful spiders provide. The best thing about Joro spiders is they eat mosquitoes! Maybe instead of Citronella torches, residents could install trellis’ and add a couple of Joro spiders. Joro spiders are also a new food source for mud dauber wasps (which are also beneficial because they eat black widows) So it looks like Joro spiders are here to stay and although they can appear intimidating they are actually a good spider!


The Featured Image

Are Joro Spiders Invasive - Joro Spider Close Up
© Kelly vanDellen/Shutterstock.com

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About the Author

I'm a Wildlife Conservation Author and Journalist, raising awareness about conservation by teaching others about the amazing animals we share the planet with. I graduated from the University of Minnesota-Morris with a degree in Elementary Education and I am a former teacher. When I am not writing I love going to my kids' soccer games, watching movies, taking on DIY projects and running with our giant Labradoodle "Tango".

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