Black and yellow spiders that construct large webs are highly beneficial residents in a home garden. Spiders that construct intricate webs are called orb weavers. The black and yellow species widespread throughout North America is commonly called a golden orb weaver or writing spider. Like all spiders, they are carnivorous predators that feed on a wide variety of insect pests in home gardens. They are not, however, dangerous to pets or people.
Female black and yellow garden spiders are much larger than males. Adult females grow up to 1 1/2 inches long, while males only grow to be 1/4 inch long. Both sexes have a conspicuous yellow pattern on a solid black abdomen. The front portion of the body -- called a cephalothorax -- has many small, shiny hairs that give it an iridescent sheen. The legs are long and slender and are generally solid black.
Argiope aurantia, or golden orb spiders, receive their common name from a habit of constructing large, complex, circular webs in home gardens. The spiders build webs in sunny areas that are protected from wind. The spiders construct webs up to 2 feet in diameter that contain an intricate network of radial structures. Once a web is constructed, the spider sits in the center of the web and spreads her legs out in pairs so that she appears to have four legs instead of two. The spider remains in the same location unless her web is continually disturbed, or if she is not able to catch enough food to support herself.
Black and yellow garden spiders are beneficial for home gardens. The spiders wait patiently in their webs for insects such as aphids, flies, mosquitoes and other pests. When an insect flies into a web, the orb weaver quickly climbs over the web and bites the trapped insect, and spins a fine silk blanket over it. Orb weavers incapacitate prey by injecting venom, which causes paralysis. The venom also starts to digest the prey before the spider eats it.
While golden orb weavers are not dangerous to humans or pets, their large webs are often annoying to deal with in outdoor working spaces. While they are able to bite, black and yellow garden spiders are not aggressive and do not bite unless provoked. Golden orb weaver spider bites result in only minor skin irritation, similar to a bee sting.