Month: September 2025

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.

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.

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

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Delightful meteorological events mark the transition from summer to autumn in the Mid-Atlantic region.  Fog created by small water droplets suspended just above the ground condense on strands of spider silk as moist air cools. Morning light reveals numerically astounding and perhaps somewhat disturbing presence of spiders whose webs usually go unnoticed in the landscape. On one such misty morning my neighbor’s pachysandra and boxwood plants were festooned with more than a dozen gossamer webs. The webs were not the typical vertical orbs of concentric circle supported by radial strands like those of black and yellow garden spiders, spotted orb weavers, or marbled orb weavers we met in previous episodes. Rather, these webs consisted of horizontal 8 by 12 inch sheets each bearing a small remarkably round funnel at one end. The proprietor of the web, a handsome dappled brown and tan spider, often perched near the mouth of the funnel. My attempts to photograph these beauties were regularly thwarted by the agile spider able to disappear down the funnel in the blink of an eye.

When threatened by a predator or bug geek, the funnel weaving spider can disappear down its funnel in hole in the blink of an eye.

Funnel weaving spiders, a.k.a. grass spiders, are often confused by name with their more famous and perfidious relatives the funnel web spiders.  The bite of the Australian funnel web spider is potentially deadly to humans whereas the bite of Agelenopsis pennsylvanica, the Pennsylvania Grass Spider, is deadly only to their tiny insect prey. It is difficult to image how a human could be bitten by these shy spiders. Despite the ability of the web to capture droplets of fog, silken strands of funnel weaving spiders cannot snare small insects. They lack the sticky polymer found on the bug-catching strands of spider webs like those large orb weavers. Instead of trapping prey, funnel weaving spiders rely on a lightning fast attack and fang-strike to immobilize hapless victims that blunder onto their web. Like many other arthropods including the praying mantis and black widow spider, the female Pennsylvania Grass Spider engages in sexual cannibalism. The she-spider often eats her mate. Why does she do this? Is she grumpy or her suitor’s performance fail to meet expectations? In a clever study scientists discovered that hungry and particularly aggressive females tended to be cannibals. More importantly, the cannibalistic females produced heavier egg cases and the eggs within each case experienced increased success of hatching. If you are female Pennsylvania Grass Spider, it pays to eat your mate. So, for humans on foggy autumn morning enjoy the handiwork of funnel weaving spiders, but if you are a male funnel weaving spider think twice about who you date.    

Acknowledgements

Bug of the Week thanks non-cannibalistic Dr. Shrewsbury for photographing and wrangling spiders for this week’s episode and Dr. Shultz for providing the identification. Thanks to Kaitlyn McGrath inquiry about mysterious webs which provided inspiration for this episode. Two excellent references “Some Commonly Encountered Pennsylvania Spiders” by Steve Jacobs and “Sexual cannibalism is associated with female behavioural type, hunger state and increased hatching success” by Aric Berning and colleagues were consulted.

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