Jennifer Schultz Nelson
Extension Educator, Horticulture
I usually write about a plant each week, but this week I found a fascinating creature in my garden that sparked my curiosity. I noticed a large yellow and black spider had built a web at least two feet in diameter, anchored between my air conditioner and marigolds!
I had never seen a spider so large–it was easily two inches long. I suspected this was the garden spider I'd heard my mom talk about occasionally. But I'd never seen one. A little research confirmed the identity as the Garden Spider, Argiope aurantia.
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.
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, and 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.
The Garden Spider eats her web each day and builds a new one. She will eat just about anything trapped in her web, even insects larger than herself!
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 female lays an egg sac in the fall that is up to an inch long and contains thousands of eggs. The eggs hatch, but the spiderlings stay in the sac over the winter and disperse in the spring.
Garden Spiders' bites are harmless to humans, though they may cause some soreness, itching and swelling.