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Tales from a Plant Addict

Fun (& a few serious) facts, tips and tricks for every gardener, new and old.

Garden Spider Argiope aurantia


There are certain topics that we field questions on quite regularly at the Extension office each growing season. Unusually large insects fit this category-- they are something that stop a lot of homeowners in their tracks and prompt them to bring us a specimen or send us a picture, usually with worried commentary about whether the creature is dangerous to them or their garden.

As the growing season begins to wane, you may be shocked to find not an unusually large insect, but an unusually large spider taking up residence in and around your garden. I remember the first time I noticed the large yellow and black spider in my garden—it was easily two inches long, and its web was at least two feet in diameter!

A little research confirmed the identity as Argiope aurantia, commonly called a garden spider. The large spider taking up residence in my garden is the female of the species. The male is much smaller and quite inconspicuous. Often males are found lingering on the edge of the female's web.

My husband is a confessed arachnophobe—he is deathly afraid of spiders. His reaction to our large garden guest was to find the nearest shoe and start swinging. I stopped him before he could cause any harm and convinced him to offer the spider a stay of execution. Though these spiders may be a bit scary due to their size, they are one of the "good guys". They consume all sorts of insects, many of them the same insects that attack the beloved plants in our landscapes.

As with many spiders, the garden spider's web is an example of the incredible beauty and engineering found in nature. Garden spiders are one of a group of spiders called the "orb" spiders, meaning they spin circular webs. Garden spiders will build their webs in the same location all season long unless they are frequently disturbed or are not catching adequate amounts of food.

A garden spider's web typically starts with strands of silk at four to five anchor points that meet in the center of what will be the web. She will add several more strands of silk radiating out from the center, much like the spokes of a wheel. Spiraling out from the center she adds a different type of silk that is sticky for catching prey. This process takes several hours through the night.

Just constructing one web is amazing enough, but the garden spider eats the sticky center section of her web each day and builds a new one overnight. Some entomologists hypothesize this is one way for the spider to recycle the chemicals used for web building, others theorize that the small bits of insects and other organic matter trapped in the web each day are an additional source of nutrition.

A distinct feature of the garden spider's web is the thick zig zag of silk down the center of the web. This silk is called a stabilimentum. Scientists have observed that spiders that catch prey during daylight are the only ones to build stabilimenta; so it is thought to offer the spider some protection by camouflaging it, distracting predators, and alerting larger creatures like birds to the presence of the web so they don't accidentally destroy it while moving through the landscape.

The stabilimentum may alert prey to the presence of the web as well, and cost the spider a tasty meal. Researchers have observed that hungry spiders are less likely to build stabilimenta.

A garden spider will eat just about anything trapped in her web, even insects larger than herself! She sits in the center of her web, head facing down, waiting for prey. While her eyesight is poor, she is very sensitive to vibrations caused by prey entangling themselves in her web. She injects the prey with paralyzing venom and covers it with silk to save it for later consumption.

Given its large size, many people immediately start worrying about being bitten by a garden spider. Garden spiders are not aggressive, but they may bite if grabbed. Their bite has been compared to that of a bee sting, causing some soreness, itching and swelling. Those with compromised immune systems, the very young, and the very elderly should exercise some degree of caution around garden spiders, much like you would around a beehive.

We usually don't notice garden spiders in the landscape until late summer and early fall when they have matured. Earlier in the year young immature garden spiders build smaller webs in low vegetation. As they grow their webs get bigger and are placed higher and higher in the landscape.

The garden spider tends to build webs in calm areas out of the wind. This may be one reason that garden spiders like to build their webs under the eaves or on our front porches.

Garden spiders in our part of the U.S. will die when freezing temperatures return. The female lays one or more egg sacs in the fall that are up to an inch long, containing thousands of eggs. The eggs hatch, but the spiderlings stay in the sac over the winter and disperse in the spring.

If you find a garden spider in your landscape this year, count yourself lucky to be able to observe not only a fascinating creature, but a natural source of insect control for your landscape.

 



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