Joro spiders have been found in parts of the US southeast for the past nine years, but new research suggests they will soon be found along most of the eastern seaboard. Scientists aren't too concerned, as these spiders are awesome.
Evidence shows that Joro spiders are capable of withstanding the harsh winter temperatures found along the U.S. East Coast, and that residents in these areas can expect to see an influx of these. The spider is native to Japan, Korea, Taiwan, and parts of China. The scientists behind the study say that Joro spiders don't represent a threat to the local ecology or humans, and that we need to get used to them.
Benjamin Frick, a co-author of the study and an undergraduate researcher at the University of Georgia, told UGA Today that there was no reason to actively squash them. Don't blame the Joro spider.
Joro spiders have long black legs with yellow streaks and large bodies in blue, yellow, and red. They are also known for casting bright, golden webs. Adult females can grow to between 17 and 25mm in size, while males can grow to between 7 and 10mm. Joro spiders won't bite unless threatened. Their fangs aren't often big enough to pierce human skin.
Scientists don't know much about how Joro spiders have adapted to their new American habitats. The golden silk spider (Trichonephila clavipes) took root in the U.S. southeast 160 years ago. The tropical spider has not spread much beyond the southeast as it can handle the cold. The purpose of the new study was to compare the two spiders to see if they were the same. Scientists learned that the answer is no.
The records submitted to iNaturalist.org allowed them to compare the seasonal spread and timing of the spiders. They looked at the actual specimen, taking measures of metabolism and heart rates to evaluate their environmental tolerances. The spiders were exposed to freezing temperatures for two minutes.
According to the study, Joro spiders have a shorter season than golden silk spiders and can complete their lifecycle within a narrow period of suitable weather. Joro spiders have a metabolism that is twice as high as their cousins, and their heart rate is higher when exposed to low temperatures. Half of the golden silk spiders were able to survive sub-zero temperatures. The scientists wrote in their paper that the results suggest the Joro spider can exist in a colder climate than the southeastern USA.
It would seem that the northern spread of Joro spiders is inevitable. In areas of Japan that are similar to the U.S. eastern seaboard, these spiders thrive, and they spread using a technique called ballooning, in which they use the wind to carry them to new locations. It is likely that humans will spread them as well, such as on transport trucks or inside luggage.
They don't think that Joro spiders exert too much of an effect on local foodwebs, and that they might actually represent a new food source for birds. People should leave the arachnids alone.
If they are in your way, I can see taking a web down and moving them to the side.
The Joro spider might add to the ecological diversity of North America because we are used to seeing invaders as being negative. Time will tell.
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