The black and yellow garden spiders become very active toward the middle of August, here in Illinois. Their huge orb webs (up to 2 feet in diameter) can be found nearly anywhere there are tall weeds. Argiope spiders are carnivorous predators, active in the daytime, attacking insects that are trapped in their web. The spider hangs, head down, in the center of their web while waiting for prey. Often, she holds her legs together in pairs so that it looks as if there are only four of them. Sometimes the spider may hide in a nearby leaf or grass stem, connected to the center of the web by a nonsticky thread which quivers when prey lands in the web.

Argiope spiders often add stabilimenta, or heavy zig-zagging portions, to their webs. Stabilimenta are conspicuous lines or spirals of silk, included by many diurnal spiders at the center of their otherwise cryptic webs. It has been shown spider webs using stabilimenta catch, on average, 34% fewer insects then those without. However, webs with the easily-visible markings are damaged far less frequently by birds flying through the web. It is an evolutionary tradeoff the spider can influence every time it builds a new web. The inclusion of stabilimenta is influenced by many factors, including prey density and web location.  Read the scientific study at Behavioral Ecology magazine.

In any event, stabilimenta or no, a large Argiope planted firmly head-down in her web amongst tall weeds and grasses remains maddeningly invisible to man and beast. The black and yellow markings of the fat abdomen and striped legs function as camouflage much like the tigers' stripes do in the jungle - the geometric elements serve to break up the outline of the spiders' body and confuse the eye of the beholder into not recognizing the image. It is this principle upon which warships' hull camouflage was painted during the World Wars, with stark diagonal lines and shapes intended to keep an enemy from discerning the outline and identifying the size of the ship and the extent of its armaments.