Joro Spiders: A Growing Presence in the United States

The Joro spider (Trichonephila clavata) is spinning its three-dimensional webs across porches, power lines, gardens, and vegetable patches throughout the Southeastern United States. Joro spiders, an invasive species from East Asia, have become well-established in Georgia and are spreading throughout the Southeastern U.S. While their appearance can be alarming due to their size and bright coloration, they are generally considered harmless to humans. Birds, lizards, frogs, bats, and some wasps are known to prey on Joro spiders. Some experts believe that the Joro spider’s rapid spread in the U.S. is in part because their predators haven’t yet fully adapted to utilizing them as a food source. Continue reading to discover more about the Joro spider and the threats it poses.

Arrival and Spread

According to the University of Georgia, Joro spiders were first observed in Georgia in 2013. The official hypothesis is that Joro spiders arrived in the United States in a shipping container. It is believed that the spiders arrived in a shipping container that was dropped off in Braselton, Georgia.

Since its arrival, the Joro has spread dramatically and has been reported in at least 10 U.S. states, including Georgia, South Carolina, North Carolina, Tennessee, Alabama, Maryland, Oklahoma, West Virginia, Pennsylvania, Florida, Kentucky, and Mississippi. The spiders are in rural wooded areas and urban areas, primarily around houses.

Joro Spider: Overview

Joro spiders are orb-weavers, a type of spider that spins a distinctive, circular orb-shaped web. These spiders, belonging to the family Araneidae, are common in gardens, fields, and forests. Female Joro spiders are significantly larger than males. Females can have a body length of about 0.66 to 1 inch and a leg span of up to 4 inches, while males are much smaller, with a body length of around 0.27 to 0.39 inches. They also have a much smaller leg span compared to females. Male Joro spiders have a brown body, while females are distinguished by bright blue, yellow, and red markings covering their abdomen.

Females deposit sacs of between 400 and 1,500 eggs in the fall, typically between September and November. When the eggs hatch in the spring, the hatchlings disperse by riding the wind on strands of silk, allowing them to colonize new areas.

Are Joro Spiders Invasive?

Joro spiders are a non-native species that have become increasingly prevalent in the Southeastern United States and are now spreading across the Eastern Seaboard. They are generally considered harmless to humans, with bites causing minor irritation similar to a bee sting.

However, the scientific community agrees that it is too soon to draw conclusions about the Joro spider’s impact, and further research is needed. A study at Clemson University in South Carolina suggests that it is too early to determine whether this non-native species will have negative consequences for South Carolina’s ecosystems. Joro spiders are expected to continue spreading across the U.S., particularly along the East Coast. The Joro spider is considered an invasive species in the United States.