The nomadic jorō spider (Trichonephila clavata) first made ground in the United States back in 2014, likely after arriving via shipping container, and has since has been ballooning its way across its newfound home (that's right, spiders can fly). Now believed to have taken up residence in at least 25 counties from Georgia to South Carolina, it seems the jorō spider may be a permanent residence across much of the East Coast.
The invasion isn’t without precedent, as the closely-related golden silk spider (Trichonephila clavipes) successfully moved into the same region over the last 160 years. Now, a paper published in Physiological Entomology examined whether the success of this spider could be used to map the future residential status of the jorō spider in the US.
To determine the likelihood of a jorō spider takeover, they compared its biology and physiology to the golden silk spider to see if it would be similarly contained to the southeastern united states. It’s believed that the latter never spread beyond this region owing to its penchant for tropical climes presenting thermal limitations to its range.
Snatching up specimens and looking to reports of jorō spiders on iNaturalist.org, researchers ascertained how their heart rate, survival, and metabolism compared to golden silk spiders. They also looked at the length of their lifecycle, which could indicate how likely the species are to be killed off in a cold snap.
Their results showed that jorō spiders have an inherently higher metabolism – twice that of golden silk spiders – and a heart rate that was 77 percent higher in cold temperatures, both of which would contribute to surviving in colder weather.
Freeze tests supported this, showing that they had a survival rate of 74 percent in a brief cold snap compared to just 50 percent among golden silks.
Jorō spiders also complete their life cycle in a comparatively shorter amount of time, meaning they need just a small window of good weather to keep the good times rolling.
“These findings suggest the jorō spider can exist in a colder climatic region than the southeastern USA,” conclude the study authors, which they say “can be useful information for management or planning purposes.”
As for what to do if you find the jorō has landed in your back yard, corresponding author Andy Davis from the Odum School of Ecology at the University of Georgia says resistance is futile.
“People should try to learn to live with them,” he said in a release. “If they’re literally in your way, I can see taking a web down and moving them to the side, but they’re just going to be back next year.”
The Jorō is so named after the legendary spider Jorōgumo which, in Japanese folklore, dominates men by shapeshifting into a woman as a means of luring them into their web. It’s perhaps fitting, then, that its namesake is making such quick work of claiming parts of the USA.