In these photos you see three different examples of Argiope sp. that is common to North Central Texas. All are females because of their large size. The photograph above shows an Argiope in the center of her dew-covered web. Notice how large the web is relative to the 3 inch spider (leg tip to leg tip). She is also located in the center of her web which is characteristic of the genus Argiope. The round web is made by members of the Araneidae family, or Orb-
Weavers. Argiope spiders are one of the biggest spiders that can be found in Texas.
The picture below shows a different Argiope sp., on her web, up close. Note the markings on the abdomen and the black and yellow legs.
The last photograph shows another Argiope sp. perched on her refuge in the center of her web and the zig-zag silk structure known as the stabilimentum. A discussion of its function is found in Wikipedia here.
As in much of science, there are puzzles, and lots of conjecture about how to solve them. I wonder if stabilimenta serve more than one of the functions listed in the Wikipedia article in the link above. You may also wish to read the research paper of Todd Blackledge and John Wenzel in Behavioral Ecology found here that discusses some interesting findings. Maybe you will be the researcher who answers this question.