The Joro spider (Trichonephila clavata), a large-bodied orbweaver native to east Asia, has become a prominent topic of discussion due to its increasing presence in the United States, particularly along the east coast. First recorded in the US around 2010, this invasive species has sparked curiosity and concern regarding its potential impact on local ecosystems. This article delves into the dietary habits of the Joro spider, shedding light on what these arachnids consume and how their feeding preferences might influence the environment they now inhabit.
Joro Spider Basics
The Joro spider is an orb-weaving spider, constructing spiral, wheel-shaped webs to capture its prey. Female Joro spiders are notably larger than their male counterparts, with bodies measuring around 2.8cm long and legs stretching approximately 3cm. While they possess venom used to subdue insects, Joro spiders are considered shy and not readily inclined to bite humans. It is thought that the Joro spider was introduced to the US state of Georgia around 2010, most likely arriving in a shipping container. A female Joro spider can lay between 400 and 1,500 eggs in a year. They hatch in the spring, mature over the summer, and often die off by late fall or early winter. Joro spiders use two primary methods to move around. One method is by hitchhiking with humans - winding up in cargo shipped around the world and finding their way to new lands. The other method is through a process known as ballooning. Ballooning is when newly hatched spiderlings climb as high as they can, stand on raised legs, and then release several threads of silk from their spinnerets. These thin silk threads act as a parachute, allowing the spiderlings to travel with the wind as they are swept up in air currents.
A Varied Diet of Invertebrates
Joro spiders primarily feed on other invertebrates that become ensnared in their webs. Their diet includes a variety of insects, such as:
- Cockroaches
- Beetles
- Bees
- Mosquitoes
- Stink bugs
- Yellow jackets
- Biting flies
As passive hunters, Joro spiders wait for insects to get tangled in their webs, after which they wrap the prey in silk and use venom to subdue it. Much like typical orb-weaver spiders, Joro spiders eat a variety of small insects. The protein and nutrients from insects are vital to the Joros diet.
Monarch Butterflies: A Notable Exception
Interestingly, research suggests that Joro spiders avoid consuming monarch butterflies, despite the abundance of these butterflies during the spiders' peak season in late summer and fall. Monarch larvae feed on milkweed, they sequester cardiac glycosides into their adult tissues, rendering them unpalatable to many predators. Studies have shown that Joro spiders attack monarchs far less frequently than other butterfly species, such as gulf fritillaries and tiger swallowtails. In some instances, the spiders even remove monarchs from their webs.
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This behavior raises questions about how Joro spiders, without prior experience, recognize the unpalatability of monarchs. It's worth noting that monarch butterflies are not native to the Joro spider's native range in East Asia.
Implications of the Joro Spider's Diet
The Joro spider's diet may have several implications for the ecosystems it invades. They might impact native ecology by competing with native spiders for food. This spider species could also help control invasive species like stink bugs and spotted lanternflies. While they may displace native spiders, some entomologists believe their ecological impact will be mild.
Joro Spiders and Humans
Despite being venomous, joro spiders are not dangerous to humans or pets. These pests won't bite unless cornered, and even if you are unlucky enough to experience a bite, their fangs are typically not large enough to break human skin. Unless you're allergic to the venom, there's no need to be afraid of Joro spiders. In fact, they're more afraid of you than you are of them and will run away if you disturb their web.
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