The Golden Silk Spider, Nephila clavipes, often locally called the Banana Spider (due to its body shape and color), is one of coastal Louisiana’s most conspicuous arachnids. They are also our most interesting in terms of their natural history.
Golden Silk’s typically live for one year. They begin their lives hatching from eggs inside of silken egg cases that are attached to the ends of tree branches, usually encased in leaves. These eggs and egg cases had been produced sometime during the preceding August to October. The eggs hatched about a month after being laid, and molted for the first time a week or so later. They then spent the winter within the egg case (can you imagine the intertwining of legs?). In early spring, the little spiders begin to leave the egg case and disperse. They build webs, eat, and grow.
By mid- to late summer, Louisiana woods may be full of huge Golden Silk webs. They are easily recognized due to their silk color (golden yellow), silk strength (it can be held and shaken violently without breaking), and large irregular webs. People who are afraid of spiders avoid the woods at this time of year, but these spiders are harmless, though quite large.
Typically, the female has a body length of about three inches, but her long legs with tufts of hairs at the joints makes her look bigger. She is slow moving, and does not drop from the web. The males are much, much smaller (about one inch long and much thinner), and generally shaped the same. During the breeding period, males and females will be on the web at the same time, but the female will be on one side and the male on the other. As in most spiders, they are intolerant of one another and she would eat him in a second. The whole mating dance has developed to give him a chance to mate with her before she consumes him.
Always look closely at the webs and search for a little bitty silver-rumped (rounded or cone-shaped) spider of the genus Argyrodes. They look like little droplets of mercury on the web. These little guys are called kleptoparasites, in that they make their living off the food caught by the female Nephila (they are “parasitic”) by stealing it (“klepto-“). When the female leaves food in the web, neatly wrapped in silk, these little guys slowly and softly sneak up to it, attach their own silk to it, clip her silk around the margins, lower the food to an area toward the bottom of the web, and then enjoy a feast at her expense. This is seen throughout the range, as I’ve seen these spiders together in Belize, Costa Rica, and Trinidad, as well as Louisiana and the rest of the Gulf Coast.
Back to the strong web. The silk is so strong that early European settlers thought that it might make a fine silk fabric. In fact, it did - of the highest quality. The problem is that it takes about 5000 adult spiders, and a lot of patience, to get enough silk material for one dress. The silk is collected by immobilizing the female spider, then touching her spinerets with a piece of thin wood or cardboard, then turning it over and over and twirling the silk onto it spool-like. Primitive cultures in Madagascar still do this with a much larger species of Nephila.
After mating during the summer, the males die and the females’ abdomens become very distended with eggs. When ready, they leave the web and find a bunch of leaves at the end of a twig. They then spin an egg case, deposit their eggs, then pull together a group of leaves and incorporate them in a covering web in order to conceal the egg case. This done, the female is very near the end of her life. Her abdomen is again narrow, and she progressively weakens until she finally falls to the ground, spent or dead. Soon the eggs hatch, molt, and the new members of the species continue the cycle of Golden Silk Spider life.