This is just one of the lovely Jorō spiders that now call Maryland home. Image credit: Paula Shrewsbury, PhD
We first visited the Jorō spider in March of 2022 and wondered if there was any chance that it would make its way to the DMV. Little did we know that in September of 2022 two observations of Jorō spiders in eastern Howard County would be reported to iNaturalist. Three years and some 40 sightings later, we know that Jorō spiders are happy and doing just fine in several Howard County locations, including Ilchester, West Elkridge, and Elkridge. A week or so ago, a team of scientists from the University embarked on a mission to access the spread of an awful disease known as beech leaf disease (BLD) that is killing our ultra valuable beech trees in the DMV and eastern US. Their sortie took them to a state forest in eastern Howard County near Elkridge. While searching for BLD, they discovered a remarkable colony of Jorō spiders thriving amongst the beech trees. The recent discoveries of Jorō spiders thriving in Maryland confirms a prognostication made by scientists Davis and Frick that physiological plasticity might allow Jorō spiders to escape the relative warmth of areas it has invaded in the southeastern US and expand its range northward along the eastern seaboard. With Jorō spiders merely 20 minutes away from home, how could one resist the opportunity to visit these amazing predators? The tales of how Jorō spiders and their cousin, the golden silk spider, arrived in the US can be found in previous episodes posted in 2022 and 2024.
The underside of the Jorō spider has striking red markings. Image credit: Bob Bellinger.
However, to reduce some angst associated with a large non-native spider establishing in the DMV, here are a few things you should know. These facts were first presented in a past episode. The bite of the “venomous” Jorō spider will be terrible and painful, right? Nah, according to expert Rick Hoebeke, the risks to humans and pets are small due to the puny size of Jorō’s fangs, which are unlikely to pierce our skin. As you will see in this week’s video, I have visited Jorō and found the large females to be completely non-aggressive.
A secondary forest in eastern Howard County has been colonized by Jorō spiders. Their haphazard webs a littered with the remains of former victims, leaves, and shed exoskeletons. The much larger female Jorō spider dwarfs her mate, positioned just above her. See if you can spot a strand of silk produced by the spinnerets on the underside of her abdomen near the red mound. Relative to my hand, you can see how large and how docile Jorō is. We will wait and see what the Jorō spider means to ecosystems here in the DMV. Maybe they will help other spiders put a beat-down on invasive pests like stink bugs and spotted lanternflies. Video by Mike Raupp and Paula Shrewsbury
These spiders are passive hunters that build enormous webs, larger than a meter in diameter, to capture prey snared in the silk. For arachnophobes these may be scary, but for arachnophiles these are beautiful spiders which may provide important ecosystem services including biological control of crop pests such as brown marmorated stink bugs or spotted lanternflies, with which they have an ancient association in their native range in Asia. Jorō spiders may be likened to Hannibal Lecter "having an old friend over for dinner" when they reunite with the stink bug or lanternfly here in the US.
Despite what you may have heard, the Jorō spider is docile and poses no known threat to humans or pets. Image credit: David Coyle
Large spiders like these may also become juicy prey items for feathered and non-feathered reptiles. As with all non-native species that arrive in our land, it is difficult to predict what impact they will have on our ecosystems but experts suggest that beyond their somewhat scary mien, they may give our indigenous large orb weavers like the black and yellow garden spider, marbled orb weaver, and spotted orb weaver a run for their money. In locations in other parts of the world where Jorō is established, it often becomes the most abundant and dominant orb weaver. What will it mean for our resident spiders and their ecosystems? Only time will tell.
One final tidbit about Jorō comes from Japanese folklore. Jorō is a shapeshifter known as Jorō-gumo. Jorō-gumo turns into a beautiful woman, seduces men, binds them with silk, and devours them. Yikes! Sounds like a bad date to me.
Acknowledgements
Bug of the Week thanks Rick Hoebeke for identifying Jorō as it arrived in the US and for providing insights into the ways of these large, beautiful spiders. We also thank David Coyle and Bob Bellinger for sharing great images and knowledge of Jorō. Fascinating studies entitled “Veni, vidi, vici? Future spread and ecological impacts of a rapidly expanding invasive predator population” by David R. Nelsen, Aaron G. Corbit, Angela Chuang, John F. Deitsch, Michael I. Sitvarin and David R. Coyle, “Physiological evaluation of newly invasive Jorō spiders (Trichonephila clavata) in the southeastern USA compared to their naturalized cousin, Trichonephila clavipes” by Andrew K. Davis and Benjamin L. Frick, “Nephila clavata L Koch, the Joro Spider of East Asia, newly recorded from North America (Araneae: Nephilidae)” by E. Richard Hoebeke, Wesley Huffmaster, and Byron J Freeman, and “The Life Cycle, Habitat and Variation in Selected Web Parameters in the Spider, Nephila clavipes Koch (Araneidae)” by Clovis W. Moore ND provided the inspiration for this story and details surrounding the stars of this episode. We thank Dr. Dave Clement, Miri Talabac, and Maddie Potter for hooking us up with the colony of Jorō spiders.
To see other large orb weavers and to differentiate them from the Jorō spider, please click on this link: https://resources.ipmcenters.org/view/resource.cfm?rid=27877
To hear more about the Jorō spider and calm your fears about Jorō, please click on this link to Jorō guru David Coyle’s take on this spider: https://youtu.be/zhO_bwwg-E4?si=nhd9au-t-HRCmw6b