The Joro spider, Trichonephila clavata, is a golden orb-web spider. Females build large webs, which are often gold or yellow colored, to capture food (prey) to eat. Joro spiders are native to Japan, China, Korea, and Taiwan, however are also found in other parts of Asia.
Invasive means that a species is introduced to a new ecosystem and is or has the potential to cause economic harm, environment harm, or harm to human health. The effect that Joro spiders are having is currently being evaluated by researchers.
Male and female Joro spiders look very different. Females are easier to recognize. When fully grown, females are large, very brightly colored spiders that are yellow with blue-ish, green horizontal bands and have a large red mark on the bottom side of their abdomen. Their legs are black with yellow-orange bands, though they are rarely all black. Males are much smaller (<⅓ the size) than females, and will be seen in the fall in webs, sometimes multiple males in one female web. Visit the Species Info page for images and descriptions of Joro spiders and lookalikes.
Ballooning is one way that small spiders travel. Typically young spiders (juvenile/spiderlings) will produce or exude a thread of silk. If the silk is captured by the wind, the spider and silk will be lifted into the air and carried by the air current. Young Joro spiders can balloon. Because mature females are large, and therefore weigh much more than a spiderling, this is an unlikely travel method for adults.
Fast spread over large areas is likely due to humans unknowingly moving Joro spiders or Joro spider eggs to new locations. On their own, Joro spiders may travel over short distances (a few miles).
All spiders are venomous. Their venom is injected into prey upon capture in their webs in order to subdue the prey. So is the case with the Joro spiders. There are currently no records of harm to humans. From our experience collecting hundreds of these spiders, having them in our hair and wandering on our arms, and interacting with thousands of webs, they have not bit. In general, these spiders are timid and non-aggressive, so the likelihood of being bitten is low unless provoked needlessly.
Joro spiders likely eat any insects that fly into their webs such as moths, flies, mosquitos, bees, wasps, beetles, and stink bugs.
While there are accounts of hummingbirds getting caught in other spider’s webs, these are extremely rare occurrences. To date, there have been no confirmed published reports or articles of either birds or bats being captured in a Joro spider web. Although Joro spider webs are large, humminging birds and bats likely fly through their web rather than get caught in the web.
We recommend removing webs around bird feeders, bird baths, and flowers that you’ve noticed hummingbirds visit.
Report it! Understanding where Joro spiders are currently NOT found is just as important as understanding where we do find them! This data allows scientists to know where the spider hasn’t been found. It can help them understand more about the spider’s needs, behaviors, and more! It can also help scientists understand how fast and in what directions the spider is spreading.
Knowing where the spiders are being found (or not found!) and other information helps scientists with their research. They can use the data to see where the spiders are spreading to, the habitats they are found in, and more. They can also use the data to find locations to do further research on the spiders.