The Joro spider (Trichonephila clavata) is a large orb-weaver spider that has recently become a noticeable presence outside its native habitat. This striking arachnid often prompts questions about its size and potential impact. This article provides clear, factual information regarding the Joro spider’s dimensions, characteristics, and whether it poses a threat.
Measurements and Distinctive Features
Joro spiders exhibit a significant size difference between males and females. Adult female Joro spiders can have a body length up to 1 inch (2.5 cm), with a leg span extending up to 4 inches (10 cm), comparable to a human palm. Male Joro spiders are considerably smaller, typically measuring around 0.25 to 0.3 inches (0.7 to 0.8 cm) in body length.
Female Joro spiders are recognized by their vivid coloration. Their abdomens display bright yellow and blue-black bands, often with distinct red markings on their undersides. Their long legs are typically black with striking yellow bands. Male Joro spiders, by comparison, have a drab brown body. These visual characteristics, combined with the large, golden-hued webs they construct, make Joro spiders noticeable.
Separating Fact from Fear
Despite their intimidating appearance and large size, Joro spiders are not considered a threat to humans or pets. While they possess venom, it is primarily used to subdue insect prey and is not medically significant for humans. A Joro spider bite is rare and typically occurs only if the spider feels provoked or is constrained.
If a bite does occur, its effects are mild, often compared to a bee sting, resulting in temporary redness and minor pain. Their fangs are often too small to effectively pierce human skin. The perception of them being dangerous stems from their large size, long legs, and their habit of building extensive, golden orb webs in conspicuous locations, such as between trees or on porch lights. These spiders are shy and docile, preferring to avoid confrontation.
Where Joro Spiders Are Found
The Joro spider is native to East Asia, including China, Japan, Korea, and Taiwan. They became an invasive species in the United States, first identified in northern Georgia around 2013 or 2014. It is believed these spiders arrived accidentally, likely by hitchhiking on shipping containers or other imported goods.
Since their initial detection, Joro spiders have spread across various states in the southeastern U.S., including South Carolina, North Carolina, and Tennessee, with reports extending as far north as Maryland and West Virginia. While young spiderlings can disperse through “ballooning,” releasing silk threads to catch wind currents, adult spiders typically spread through human-mediated transport, such as hitching rides on vehicles or transported items. Their ability to tolerate a wide range of climates suggests they could continue to expand their range across much of the eastern United States.