Joro spiders, large arachnids, have become a notable presence in the southeastern United States. These orb-weavers are recognized for their vibrant yellow and black markings, often accented with a red underside. Having arrived from East Asia, they have spread across various regions, establishing their intricate, circular webs in new environments.
Their Primary Prey
Joro spiders function as generalist predators, primarily consuming a variety of flying insects. Their diet includes mosquitoes, flies, and true bugs like the brown marmorated stink bug. They also capture yellow jackets, beetles, and moths that become ensnared in their webs. The specific types of prey they catch can vary depending on the web’s location, with webs near porch lights often yielding moths.
These spiders employ a passive hunting strategy, patiently waiting for insects to become entangled. Once prey is caught in their golden orb webs, the spider wraps the captured insect in silk and then subdues it using venom. Their webs, which can reach up to six feet in diameter, effectively trap a wide range of common flying insects.
Beyond the Usual: Opportunistic Feeding
While their diet mainly consists of common flying insects, Joro spiders also feed opportunistically on larger or less typical prey. Their robust webs, known for their strength and elasticity, allow them to capture more substantial insects. Documented instances include the capture of grasshoppers and cicadas. They have also been observed preying on other spiders, such as the small dewdrop spider, which sometimes inhabits the Joro web.
Joro spiders do not typically target large animals. Though their webs are strong, the capture of vertebrates like small birds is extremely rare and usually accidental, occurring if a weakened bird becomes entangled. This demonstrates their adaptability to consume what becomes available in their environment.
Ecological Role Through Diet
The feeding habits of Joro spiders contribute to their role as insect predators within their expanding ecosystems. By consuming a broad spectrum of insects, they can influence local insect populations. Notably, their diet includes some agricultural pests, such as the invasive brown marmorated stink bug, which can offer a beneficial aspect to their presence.
However, their arrival also introduces potential competition with native spider species for food resources and suitable web-building sites. Some experts suggest that the Joro spider’s diet might not significantly overlap with that of native spiders, as they may target insects that other species tend to avoid. Joro spiders also integrate into the existing food web by serving as a food source for native predators. Birds, lizards, frogs, bats, and various wasp species are known to prey on Joro spiders.