Where did it come from, the huge black and yellow spider hanging in the bushes along the trail? What is it? And more importantly -- is it harmful to humans? If someone is not familiar with the black and yellow argiope, or garden spider, as it is more commonly known, the first sight of one can be startling to say the least.

A large spider, over an inch in length, strikingly colored, and in a web that can be up to two feet across, the black and yellow argiope (Argiope aurantia) has unnerved more than one outdoor adventurer. Once the initial shock, or perhaps fear, passes, a closer examination reveals an intricately woven web with a remarkably decorative spider resting in the center.

Argiopes are orb weavers, a group of spiders that spin circular webs of sticky silk to capture flying insects. They take it one step further though and adorn their webs with a zig-zag stitching of silk, called a stablilmenta, woven into the middle of it. Once the web is built, an intricate process that can take a few hours, the spider, hangs head-down in the center and waits for a tasty morsel to blunder into it. Small flying insects like aphids, flies, grasshoppers, wasps and bees all make a good meal. They prefer to hunt during the day, and when day is done, the entire web may be eaten then rebuilt, often in the same place. Argiopes live in meadows and gardens, where they prefer sunny areas among tall plants.

The female, the more conspicuous of the two sexes, is the web builder, and the one we're most likely to see in late summer and early fall. As she matures and begins to yolk up her eggs, she grows in size. The male is much smaller, 1/4 to 3/8's of an inch, and until he matures, he builds a smaller web near the female. Once mature, he spends his time searching for females who are ready to mate.

After mating, the female constructs one or more egg sacs. These brown papery balls may contain hundreds of eggs and are usually attached to vegetation near the web site. Once the eggs are laid, the female dies. The young hatch in the fall, but remain in the egg sac through the winter. In spring they emerge and spend the summer building small webs in grasses and vegetation. As the summer progresses, their webs grow in size and are placed higher in the plants. This is when they become more noticeable to us.

Although these spiders might be a bit scary because of their size, they are not considered dangerous to humans. Like all spiders, argiopes use venom to subdue their prey, and they will bite if harassed. That venom, though, is apparently not particularly harmful to humans. If you find one living near your home, there is no need to be afraid or destroy it. Argiopes are not very aggressive, are reluctant to leave their webs, and they - like other spiders -are providing a beneficial service by feeding on pest insects in and around our gardens and homes.

Black and yellow argiopes are fascinating creatures. The next time one happens to come along in your yard, take time to admire its beauty and skill and be amazed at what you see.

Nancy Biegel
Outdoor Rec. Planner, ESVNWR