Relax, Giant Spider Probably Came Alone
*Potentially invasive species recently captured at a coastal business
*Spider was observed by a knowledgeable local naturalist
*Likely arrived in a floral delivery in what is thought to be isolated incident
*The identification was confirmed by the Museum’s entomologist
*Spider is now a specimen at the Museum
SANTA BARBARA, CA—A three-inch-long spider was spotted lurking in the manicured landscaping at a high-end coastal business in Santa Barbara County this fall. Although harmless to humans, the Joro Spider (Trichonephila clavata) is a potentially invasive species, as there is some evidence it can outcompete native orbweavers in southeastern North America.
The Joro Spider is an orbweaver native to east Asia. Their webs can be as wide as 10 feet. The species was observed around homes in Georgia in 2014, the first reported sighting in the United States. Since then, it has spread west as far as Oklahoma and north as far as Maryland. The discovery of one in Santa Barbara County marks the first report west of the Great Plains.
The spider was observed at a coastal business by naturalist and birding instructor Sophie Cameron, who recognized it as a female Joro Spider by its size and striking yellow, gray, and black coloration. She notified the Santa Barbara Museum of Natural History’s Schlinger Chair of Entomology Alex Harman, Ph.D., who drove to the site. On confirming her identification, they captured the spider. It is now a specimen preserved among the hundreds of thousands of insects and arachnids in the Museum’s Entomology Collection. Dr. Harman and Cameron swiftly reported their discovery to the scientific journal Southwestern Entomologist, to help other insect researchers track sightings of the species.
The female spider was immediately adjacent to an area where shipments of flowers and plants are received, which likely explains how it got there. No other webs were found near the spider, which probably arrived alone inside some plants shipped from another part of the country. Cameron will be monitoring the site, just to be sure the discovery does not reflect a more established presence by the species in California.
Although Joro Spiders are sometimes referred to as “flying” spiders because their spiderlings (baby spiders) can disperse by wind in a process called ballooning, "calling Joro Spiders ‘flying’ is ridiculous, as nearly all spiders disperse by wind,” says Harman. “Using the f-word seems to cause runaway misinformation as a story gets repeated and sensationalized.”
The Museum is not publicizing the name of the business where the spider was found, says Director of Marketing & Communications Jonah Gabriel Haas, because “We don’t want this to be about shame or blame. It could happen anywhere, and that's the point—we want to tell the story because it’s a great opportunity to raise everyone’s awareness of invasive species.” The key takeaway is that in today’s global economy full of moving people and goods, we all need to pay attention to tiny hitchhikers.
“Insects and arachnids—being very small and easy to overlook—are easily transported unintentionally,” says Harman. “Flowers, fruits, vegetables, and insects can accidentally be transported among those. In addition to things like spiders that are on vegetation, there can be insects inside wood. It’s not uncommon for wood-boring insects to be transported inside wooden pallets, furniture, or firewood. Sometimes wood-boring beetle larvae can take over a decade to mature, so those insects can pop out in a new area long after the wood was moved.”
Although humans may find invasive spiders scarier than invasive beetles, the data on invasive beetles are much more frightening, in part because cause and effect are easier to trace. “If you think of the Emerald Ash Borer, it feeds on ash trees. You can measure that the ash trees are dying because of this beetle. But spiders are generalists, mostly eating small insects trapped in their web, and it’s a lot harder to measure an overall decline in their insect prey, or a decline in native spiders getting outcompeted by invasive spiders.”
The sighting was a natural fit for Harman, as much of his own research relates to finding insects at the edges of their ranges. “Just like specimens of all the other living organisms in museums, insect collections are a great source of data for seeing how ranges change over time,” says Harman. “It's important to establish baseline data of what insects are found where, and in what habitats, to see how their distributions shift over time.”
For more information about Harman’s past research and future goals, read an interview with him on the Museum’s blog.
About the Santa Barbara Museum of Natural History
Powered by Science. Inspired by Nature. The Santa Barbara Museum of Natural History connects people to nature for the betterment of both, drawing on collections that preserve the natural and cultural heritage of the Central Coast and beyond. Founded in 1916, the Museum is a private nonprofit supported in part by philanthropy, membership, and visitors. Members visit free. For more information, visit sbnature.org.
