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Today on Animal Fact Files we’re discussing writing spiders. These spiders get their common name because they make zigzag shapes in their webs! The zigzag shape lends to their other common names like zigzag spider and zipper spider. The females have a large, black and yellow abdomen and are also known as the yellow garden spider for this reason. Other members of their genus make other kinds of shapes in their webs like crosses or a lattice, but we'll save those species for their own episode.

Writing spiders live from Canada to Costa Rica but are most common along the eastern part of their range. They take up residence in open areas, often along habitat edges, where they construct webs that can span up to two feet (61cm) across. That's longer than Chester's body! Their presence in gardens is beneficial because they help capture pest insects in their webs. Female writing spiders are larger than males and make larger webs. The ladies can reach over an inch (2.54cm) in body length while males don't even reach half an inch (1.25cm) long. Their size and the zigzag pattern in their web makes them easy to spot on warm summer days.

The conspicuous zigzag pattern in a writing spider's web is called a 'stabilimentum'. This name can be a bit misleading. One might think with a name that sounds like "stabilize" that the silk would be used for that purpose. While it was originally believed to do this, it's since been shown that the threads are only loosely attached, therefore unable to provide the stability suggested. Today, its purpose is debated. Only diurnal spiders, or spiders most active during the day, use stabilimentum which could indicate a visual reasoning behind this structure. Perhaps it makes the web more visible to other animals that might otherwise destroy it. Perhaps it's a calling card to potential mates in the area. Perhaps it helps camouflage the spider itself in its web by breaking up or extending its outline. Or perhaps different spider species use it for different reasons!

Like nearly every spider alive today, writing spiders produce venom. This venom is harmless to humans. Apart from individuals with allergies or compromised immune systems, the writing spider's bite is not fatal and about the same as getting stung by a bee. On top of all this, writing spiders are considered non-aggressive and won't attack unless provoked. They would rather run away from a large animal like a human being or predators like birds, mud daubers, jumping spiders, and more. Instead, they use their venom to subdue prey like dragonflies, damselflies, wasps, bees, grasshoppers, moths and more! They can also eat small vertebrates like geckos and anoles. Each night these orb weavers eat the middle section of their web which contains miniscule insects and other nutrients they'll utilize to reconstruct their web the following day.

Writing spiders are most commonly seen in late summer when they begin mating. Males approach females timidly and vibrate the strands of her web to make their presence known. If he's accepted, he'll offer a spermatophore and die shortly after. The female may or may not eat his remains. She'll go about constructing one to three egg sacs that hold hundreds to over a thousand eggs. These hatch inside the egg sac but the babies don't emerge until the following spring. Like many other spiderlings, baby writing spiders balloon by letting out a strand of silk and catching the wind to a new home. Overall, writing spiders live to be one year old in temperate areas, though the females can live a few years in places without a harsh winter.

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