A fast-spreading invasive spider species is making its way across the United States, and specialists say its population is likely to surge as conditions get warmer.
The spiders are large, vividly colored, and venomous, with some appearing big enough to cover a human palm. They’ve been turning up across much of the country, though the biggest concentrations of these Asian arachnids are clustered along the Eastern Seaboard.
Known as the Joro spider, they stand out from more familiar American web-builders thanks to a long, narrow, multicolored abdomen and legs that can reach around eight inches. With the next hatch approaching, millions more are expected to emerge soon.
Females create an egg sac that can hold as many as 1500 spiderlings and secure it to trees. Once spring temperatures rise, the young hatch and the species continues pushing into new areas.
New peer-reviewed findings led by Clemson University scientist and assistant professor David Coyle suggest residents in New York and New Jersey could see the most noticeable uptick in the months ahead.
In the research, the arachnologist said these conspicuous spiders are ‘here to stay’ and will ‘inhabit’ most states across the east of the country by the summer—something many gardeners may already suspect if they’ve seen unusual, oversized webs and bright-bodied spiders outdoors.
He added: “Barring some unforeseen circumstance, we expect the range of these [spiders] to continue expanding, likely to the north, and we’ve already seen that with some populations in Maryland.”
Their presence in the US—despite being native to parts of Asia including Japan and China—highlights how easily species can be transported through global trade.
According to the Washington Post, Joro spiders first arrived in the US more than a decade ago, likely after stowing away on a shipping container that made its way to Georgia.
Instead of struggling in unfamiliar surroundings, the species appears to have benefited from the fact that much of the eastern US has a climate comparable to regions where Joros already flourish.
As the population grows, reports have also begun appearing beyond their expected range, with some sightings now noted as far away as the west coast.
They’re often easy to identify thanks to their size and striking colors. Females typically have bright yellow bodies with bluish striping and red accents, while males are usually smaller and more brown in tone.
Observant homeowners have reported seeing them in the following states: