Spiders, Silk & Stabilimenta

Substantial spider webs sometimes traverse the trails at the Oslo Riverfront Conservation Area. Most often, they are the webs of a large, brightly colored golden spider (Nephilia clavipes) commonly called the the golden silk spider, the banana spider, the golden orb weaver, or the calico spider (my new favorite common name) due to the coloration of the spider itself and their often, but not always, golden silk.

The genus name, Nephilia, comes from an ancient Greek word meaning “fond of spinning”. Nephilia is the oldest surviving genus of spiders and dates back to 165 million years ago.

Spiders produce their silk from glands in their abdomens as shown above in a photo taken at the Spoonbill Marsh on 11/7/2015. Scientists have identified 7 kinds of glands that produce different types of silk that are used for specific purposes. No one species has all of the 7 different kinds of silk glands.

Webs, of course, are used to entrap prey, and below a spider photographed by Karen Schuster (Class of 2008) enjoys her meal.
The golden silk spider produces a special silk with which to “wrap up” its prey for future consumption, as you can see in the upper portion of the photo below.
Its prey includes mosquitoes (yeah!), flies, bees, grasshoppers, butterflies, dragonflies, and, perhaps, even small birds. Click here to read an account about a Acadian flycatcher ensnared in a golden silk spider web in Tallahassee.

Webs are spun by the female golden silk spiders. The larger the web, the larger the spinning spider. The central orb of the web constructed of fine-meshed, sticky silk.

The outer supporting structure, often asymmetrical, is fashioned from a a very, strong non-sticky silk. This silk reportedly is stronger than steel but not as strong as Kevlar. Click here to view a strength test video. These clever creatures adjust the pigment intensity of their silk relative to the background light & color.

Male golden silk spiders are far smaller than the females and often can be seen on the edges of the webs, as shown in this photo also taken by Karen.
Female golden silk spiders do the “web-keeping”. They will cut their webs to remove large non-prey items like sticks. Web maintenance is ongoing, and females engaged in regular maintenance activities “re-cycle” their silk. As part of the ongoing process of maintaining their web, they will consume their silk & re-use to repair their web.
Sometimes, but not always, the webs of golden silk spiders (& other species) will contain zig-zag patterns called stabilimenta in the central orb, which the spider pictured above appears to be creating. Scientists have many theories about the purpose of stabilimenta, including that they attract prey or forewarn large non-prey items (like you & me) about the presence of their web.

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