The writing spider, a common arachnid, often captures attention in gardens and yards across North and Central America. Known for its distinctive appearance and unique web patterns, it is a frequent sight during warmer months. Its presence often sparks curiosity due to its size and striking coloration. This article explores how to identify them, their unique webs, and safety concerns.
Identifying the Writing Spider
The writing spider, Argiope aurantia, is named for the golden yellow markings on its abdomen and silvery hairs on its cephalothorax. Females are noticeably larger than males, typically 19-28 mm (0.75-1.1 inches) long, while males are 5-9 mm (0.20-0.35 inches). The female’s abdomen displays a vibrant pattern of black and bright yellow, often with symmetrical patches, and their legs are typically black with yellow bands.
A defining characteristic that helps identify this species is the prominent zigzag pattern woven into the center of its web. This dense, non-sticky silk structure is called a stabilimentum, and it can appear as a vertical line, an “X” shape, or even a circular pattern within the web. Writing spiders are commonly found in sunny areas, such as gardens, shrubbery, and tall vegetation, often at the edges where two different habitats meet. They build their large, circular orb webs between plants or structures, making them easily observable in many outdoor spaces.
Its Unique Web and Behavior
Writing spiders construct large, circular orb webs, up to two feet across. They rebuild these webs daily, often consuming old silk to recycle nutrients. The most notable feature is the stabilimentum, the thick zigzag pattern near the web’s center. The exact purpose of the stabilimentum is debated, but several theories exist.
One theory suggests the stabilimentum helps to stabilize or strengthen the web, while another proposes it makes the web more visible to birds, preventing accidental damage by large animals flying through. Other ideas include that the pattern may attract prey by reflecting ultraviolet light, camouflage the spider by breaking up its outline, or even serve as a visual signal to potential mates. The spider typically rests head down in the web’s center, awaiting prey.
Writing spiders are carnivorous and primarily feed on insects that become ensnared in their sticky webs, such as flies, grasshoppers, bees, and moths. Upon detecting vibrations from trapped prey, the spider quickly moves to inject venom to paralyze it, then wraps the insect in silk for later consumption. They select web locations that offer a high likelihood of catching prey while minimizing disturbance.
Is It Dangerous?
Despite their large size and striking appearance, writing spiders are generally not considered dangerous to humans. Like most spiders, they possess venom, which they use to subdue their insect prey. However, their venom is not considered harmful to humans and is primarily used to paralyze small insects. These spiders are not aggressive and typically bite only when they feel threatened or are directly provoked, such as when handled.
A bite from a writing spider is often compared to a bee sting, causing mild symptoms like localized pain, redness, and swelling at the bite site. These symptoms are usually short-lived and resolve without serious complications. While serious allergic reactions are rare, individuals who are very young, elderly, or have compromised immune systems should exercise caution, similar to how they would around a bee or wasp. It is advisable to admire these beneficial garden inhabitants from a distance and avoid direct contact to prevent bites. Writing spiders play a valuable role in controlling insect populations, making them a helpful presence in gardens and yards.