Arkansas Nature Trivia

How a Spider Makes a Wheel-Shaped Web (and Doesn't Get Stuck on It)

By Renn Tumlison

Spiders make a variety of webs with different forms and in different locations. Each suits the lifestyle of the particular species of spider. In a home, humans usually try to remove the three-dimensional type called a "cobweb." When we walk along a trail, the "wheel" or "orb" web often is encountered (usually, too late to be avoided). The construction of such a web requires a series of logical steps, although the spider does this by instinct and does not use the human concept of logic.  

The first step is to produce and anchor the first thread. From glands in its abdomen, the spider makes a long sticky thread and lets a breeze carry it horizontally until it sticks to something. That initial thread is reinforced because it will be the main support for the web.

Another thread is attached to anchor the main thread to an object some distance below it, and a few more connecting threads stabilize the structure. These threads become the radii of the web, which may resemble the spokes of a bicycle wheel.

With the radii in place, the spider begins to circle the web with a spiral of connecting threads. At first, the threads used are not sticky, but later sticky threads are added as the non-sticky ones are removed. There are several glands in the abdomen of the spider, which produce threads for different purposes, such as threads for attaching, threads for adhesion, threads used to make cocoons, and threads used to encapsulate prey.

The spider waits at the center of the finished web. The struggles of insects that become entangled pull against the nearest radii and the spider reacts to the tight line much like a fisherman would to a tug on a fishing line. The spider runs to the location of the captured prey. Larger prey may be wrapped with threads to immobilize and store it.

During this activity, why doesn't the spider get stuck on its own web? Remember, the radii are not sticky. The spider moves along the non-sticky parts of the web and avoids the sticky parts. It also is believed that the feet are oily and not likely to become stuck on the adhesive. If the web is too damaged after a night of feeding, the spider eats it to recover the proteins invested in making the threads. The material can then be reused the following night to build a new web. Threads used in the web are very fine and elastic. The threads can stretch 30-40% without breaking. Polynesian fisherman have used spider silk as fishing line, and during WW II, threads from the Black Widow spider were used in telescopic gun sights.