The Joro Spiders Are Coming...

Robert E Furey

...and That Just May Be a Very Good Thing.

Species can move around, particularly when there are dynamic changes taking place in the environment. Organisms exploit opportunities or flee disruptions and have done so since the beginning. These shifts in a species' distribution in response to environmental change are normal and so fine and dandy. Under certain circumstances, these species can cause ecological harm. When human activity is involved with these migrations, triggering or facilitating geographic shifts, we label them with the judgmental handle, Invasive species.

Invasive species are a thing since human beings began spreading around the globe. We took other creatures with us. Some on purpose: dogs, cats, horses, potatoes, and corn for a few examples. We also took other not so welcome travel companions: mice, rats, wheat weevils, flies, and bamboo from the dark and shady side. But the list for human-mitigated migration is much longer. And unfortunately, in some cases, very bad.

Let’s briefly talk about a few.

Asian carp were brought to the United States to clean water treatment facilities holding ponds and early efforts in aquaculture. They escaped into the Mississippi River and from there the Missouri and Illinois Rivers.

Zebra mussels came to North America likely through ballast water dumped into the Great Lakes from cargo ships coming from Asia. Their spread has been rapid and relentless, filling tributaries and clogging machinery. Zebra Muscles have even managed to leave the contiguous Great Lakes system on the feet of wading birds. They are very good at spreading.

More recently we’ve had to contend with insect and spider species that appear to be taking a toehold in the Eastern United States. The brown marmorated stink bug has been devastating crops and overwintering inside people’s homes. Stink bugs are not harmful to humans or pets, so inside your home are not a danger. Although they are annoying, the smell when disturbed can be even more so. The impact on crop yields and so cost to farmers is a real issue that affects all of us.

The spotted lanternfly, too, has become a devastating invader to the ecosystem. These animals pack a double wallop in that they damage and kill trees, vines, and crops. If that wasn’t enough, the lanternflies excrete a sugary honeydew as waste that promotes the growth of a black mold that causes its own damage to plants.

Recently in the news, we’ve heard about a new expected arrival, the Joro spider. Joro spiders are large, similar to the golden orb spiders in the American South. Like the invaders mentioned above, Joro spiders come from Asia as well. We think they came clinging to shipping containers.

These animals are big and imposing, with spread legs they are larger than the size of your hand. They themselves are brightly colored. They spin strong, yellow-colored silk orb webs. And more importantly for this discussion, they can survive cold.

Our own Golden Orb spiders are larger than a Joro, yet they are restricted to more southern climes due to their own susceptibility to cold. It’s now postulated that the Joro spider will quickly spread north, particularly in states along the east. Possibly as far north as Pennsylvania.

Is this a bad thing?

Lots of people are afraid of spiders. And reasons, why this might be, are better suited to a later article. For now, we can acknowledge a fear of spiders that in many cases do not require the impressive size of an adult female Joro spider. They are large, flashy, and build large, strong webs of yellow silk. If one were to fall on you, as unlikely as it would be, you would feel it thump onto your shoulder. Not so with any other spider you are likely to encounter. But see, here’s the thing, they are harmless. They will not hurt you. They are not aggressive and even under the most unusual circumstances, were they to try to bite you, their jaws cannot pierce your skin.

So is there any reason to be concerned about the pending arrival of Joro spiders? None at all. In fact, these animals will help us in that they prey on those invasive stink bugs and the devastating lanternflies. So not all accidental introductions are going to be bad. And sometimes an organism comes in and finds old friends to eat, like the Asian Joro discovering the lanternflies and brown stink bugs from home.

So if you are lucky enough to see a Joro, enjoy the sight of a truly spectacular animal. You don’t need to kill it as it probably barely knows you’re there. So take a picture and brag to your neighbor that you have a Joro in your garden and that you are doing your part in reducing the toll taken by those nasty invasive species.

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Associate Provost of International Relations and Professor of Integrative Science at Harrisburg University. Forensic Entomologist / Deputy Coroner for Dauphin Co, Pennsylvania. Writes about science, travel, and society.

Harrisburg, PA
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