The yellow garden spider (also known as the writing spider, zigzag spider, or zipper spider, among others) is the species Argiope aurantia, known for their striking black and yellow patterning. They are in the Araneidae family of “orb weaver” spiders. While all spiders make silk, not all make webs, and while some make webs, orb weavers stand out with their beautiful wheel-shaped webs.
Most spiders have two claws on each foot, but orb weavers have an extra claw that helps them create more complex webs. Some orb weaver webs include a conspicuous zigzag pattern that has had passersby and scientists alike wondering about its purpose.
These silky decorations are called stabilimenta because of an outdated hypothesis that they stabilize the spider’s web. It turns out that this extra silk is laid too loosely on the web to strengthen it, and can even be removed without disturbing the constructive function of the web.
Another hypothesis is that stabilimenta attract insects by reflecting UV light. One study found that webs with stabilimenta attracted more insects, and in field observations, such decorated webs tended to have more prey in them. Alternatively, in one controlled experiment by Dr. Todd Blackledge at the University of Akron, webs with stabilimenta caught 30% fewer prey. His reasoning was that while UV light reflection makes the web more apparent, it isn’t necessarily more attractive; the web just becomes easier to see and avoid.
Contrary to standing out, it’s also possible that orb weavers use stabilimenta as a defense as they sit in their webs for days at a time. Stabilimenta may break up their body outline, camouflaging the spiders from hungry predators. Stabilimenta shape varies widely depending on orb weaver species, appearing as large X patterns, or long “zippers”, or entire circles of zigzag silk. The reason for this? Well, maybe that’s just pure spider artistry!
Suzana Diniz and Vanessa Stefani, 2016.
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