FAYETTEVILLE — "Giant." "Venomous." If those adjectives weren't enough to pique America’s arachnophobic interests, some are also tagging joro spiders as “flying.”
Sensational headlines are popping up across the country about the latest species introduced to the US, the joro spider Trichonephila clavata.
However, these sensationalized claims, just like the spiders themselves, do not have wings, and as with much of the news today, there is less to worry about than headlines suggest.
What are joro spiders?
Joro spiders are an impressive-looking species of orb-weaving spider with females exhibiting bright yellow markings on their body and legs. Orb-weavers create the iconic angular-yet-circular spider webs that are often depicted in everything from children’s books to low budget horror films.
The spider family Araneidae (A-rain-E-ah-day) contains about 3,500 species of orb-weavers, with more than 150 species being native to the US. The closest native relative of the joro spider is very similar in overall body shape, habits, and size, and is known as the golden orb-weaver — Trichonephila clavipes. Golden orb-weavers have actually been farmed for silk production and females can be separated in appearance from joros by coloration that is less striking and presence of obvious tufts of hair on three of their four pairs of legs.
Other native orb-weavers and friends of the garden, the garden spiders — Argiope aurantia and A. trifasciata — could also be mistakenly identified as joros by the public as they are also large and colorful yellow and white orb-weavers. Garden spider females can actually get larger than joros and can be differentiated by how their web contains a zig-zag pattern reminiscent of a zipper that runs right up the middle of the orb web. This structure is called a stabilimentum.
Are they giant and can they fly?
Of course, “giant” is relative, but it would probably only be used to describe the mature females that can reach a body length of about 1.25 inches, not including legs. So, these are not carry-away-your-pets-kind-of-big by any means, but quite a bit larger than jumping spiders or black widows for instance. Females still fall far short of tarantula size and males would not be noticed by most people as they lack the striking coloration of the females and only reach a little over .25 inch in body length.
As for the flying, well technically, no, they cannot fly, and adults will never be airborne unless they have fallen or been picked up by wind, just like any other spider could.
However, baby joro spiders do partake in an activity known as ballooning. This is when the tiny and very lightweight spiderlings push out some web into the breeze and catch it much like a miniature kite. Where ballooning spiders land is generally up to the winds of fate instead of targeted destinations.
It has also been shown that some spiders can not only balloon on wind currents, but also electromagnetic fields. Could a joro spider land in your yard from the sky? Sure, but would an individual be enough for you to notice upon landing? Probably not. Each spring, overwintering egg sacs will spill forth with tiny ballooning daredevils that, if successful, will become mature by fall and will perish in late autumn or winter.
Where are joro spiders found?
Joro spiders are native to Japan and many other parts of Asia and are not known to have been reported in Arkansas at the time of this article. However, a lone report from Bartlesville, Oklahoma, was made on the app iNaturalist with the user mentioning that it was likely transported from a recent road trip to Athens, Georgia, (so it probably came through Arkansas!).