Giant Yellow Spiders Spotted Across Maryland — Researcher Urges Public To Report Sightings

CHESTERTOWN, Md. — A Washington College biologist is asking residents in the Baltimore area and on Maryland’s Eastern Shore to help map the spread of the Jorō spider, an invasive orb-weaver that has begun establishing a separate Mid-Atlantic population.

Angela Chuang, an assistant professor of environmental science and studies and biology, said she is studying a distinct Northeastern population first documented near Elkridge in 2022. She’s asking the public to photograph and report sightings through the iNaturalist app to gauge how quickly and widely the species is spreading.

“The main thing is, we would like it if people could report when they see these spiders, so we have a better understanding of how Jorō spiders are spreading around, especially because this is a distinct population from the older one,” Chuang said. “It represents an opportunity to study an invasive population at its earliest stages.”

Jorō spiders (Trichonephila clavata) are large, bright yellow-and-black orb-weavers native to Asia. They can be confused with the similar-looking, native yellow garden spider. Adult females—often reaching leg spans up to four inches—are most visible in late fall.

Chuang said climate and ecosystem differences mean Maryland’s population dynamics may not mirror patterns reported in the South, where most early U.S. research occurred. “We’ve found that just because competition or something is happening with native spiders in the South, it doesn’t guarantee it will happen here,” she said. Her current focus is assessing whether Jorō spiders are impacting native spider communities; early observations show they can become numerous within a few years of arriving at new sites.

Chuang noted the species is not considered a health or safety threat to people or pets. Prior work she contributed to found little to no reaction in rare bite reports. “We hope these studies teach people some of the dos and don’ts around managing these spiders and go a long way towards alleviating any personal safety and health concerns around them,” she said.

How to report a Jorō spider
• Download iNaturalist (iOS or Android) and create an account.
• Take clear photos of the spider and web; the app records date, time and location.
• Submit the observation as “Jorō spider” or “spider”; the community will help confirm.

Chuang encourages residents to look now while large females remain visible into late November and, weather permitting, early December. Baltimore and Eastern Shore residents interested in field verification can email photos and site details to JoroSpidersWC@gmail.com.

More information on Chuang’s research is available on Washington College’s biology department website.

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