Can palm-sized Joro spider survive Michigan winters; Expert weighs in

There could be a new spider in town, and it’s a really big spider. But will it make it through a Michigan winter? Let’s see what a researcher thinks.

The Joro spider is a spider native to Japan. It showed up in Georgia about eight years ago. The spider made the trip from Japan in some container with items shipped from Japan. In the past eight years the Joro spider has expanded from one sighting in Georgia to living across a large area of north Georgia. A natural expansion of living area to Michigan could take 20 years, according to Andy Davis, Ph.D., Assistant Research Scientist, The University of Georgia.


Joro spider (photo provided by Andy Davis, Assistant researcher at The University of Georgia)

But Davis admits the Joro spider will probably not wait 20 years to visit Michigan. The Joro spider will likely show up in Michigan someday soon as a hitchhiker in luggage or in a vehicle.

Davis says the summer is no problem for the Joro spider. He wanted to know if the Joro would survive the colder winters of the northern U.S. So fellow University of Georgia researcher Benjamin L. Frick and Davis studied the metabolism of the spider in hopes of developing a winter hardiness picture.

The Joro spider was compared to another initially non-native spider, the golden silk spider. The golden silk spider now has around 160 years of living in the U.S. Davis and Frick found the Joro has a few characteristics pointing toward more cold hardiness than the golden silk spider. The researchers evaluated the Joro’s respiration, heart rate and ability to survive two minutes of 30 degree temperatures.

Of course the spiders would have to survive more than two minutes below freezing here in Michigan.


Joro spider (photo provided by Andy Davis, Assistant researcher at The University of Georgia)

The research showed that the above vital signs pointed toward the Joro being able to survive in colder weather than Georgia.

Davis then looked to the weather in the Joro’s native land, Japan. Davis told me the Joro has been found in Japan all the way up to the northern tip of the country. Davis then said the latitude of the northern tip of Japan is 45 degrees North latitude. The 45 degree North latitude line runs across Michigan from near Leland to Bellaire to near Alpena.

Davis said he looked at this past year’s weather at Grand Rapids and Aomori, Japan. Aomori is one of Japan’s northernmost cities, and Joro spiders live there. Grand Rapids has a similar climate with just February being colder.

Davis admits it’s still uncertain, but here are his thoughts on the Joro spider living in Michigan. He says the adult spider can probably survive a Michigan winter. The adult spider having surviving babies will possibly not occur. The adult spiders would live through a Michigan summer and fall, and then lay eggs. The egg sack is about the size of a pea, and like a spider sleeping bag, according to Davis. The egg sack could freeze in the winter, and the unborn spiders wouldn’t survive.


Joro spider (photo provided by Andy Davis, Assistant researcher at The University of Georgia)

Davis says the spider won’t be a harm to humans if it makes it to Michigan. It’s not a dangerous spider to humans, but could change Michigan’s ecosystem by becoming a predator to some of Michigan’s native insects.

He also wants to emphasize the Joro spider won’t be falling out of the sky on top of you. In recent days there have been articles calling this a parachuting spider. Davis says the correct term is ballooning. Ballooning happens when the babies hatch. They send out a long thread into the wind that the babies travel along. The babies are so small at that point that you wouldn’t even know it’s happening.

But if the babies turn to adults, or you run into an adult, you’ll find a web up to three feet across and a spider the size of your palm.

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