When the temperature gets hot, the orb-weavers come out, stretching their webs taut and hoping for a tasty visitor. The female Golden Silk Spiders (Nephila clavipes) are among the largest non-tarantula spiders in North America and are perhaps the largest orb-weavers in this country. I think they’re beautiful. I love this time of year because they just sit there and patiently pose for my camera.
This week I found a three-sided spider web cathedral, or at least it seemed like that to me. There is a large oak tree near my house with limbs spread wide, creating shade all around it. Two Golden Silk Spiders stretched their webs from the tree limb to the ground, creating walls made of silk. The trunk of the oak tree completes the building as the third wall.
I couldn’t resist. I ducked under one of the walls and stood up in the center of the cathedral with my camera. To my right, about six inches from me was the large female in the picture above. To my left and about a foot above my head was a slightly smaller female. They’re shy, and I tried not to disturb them, but it was still slightly intimidating to be that close.
I was focusing my macro lens on the big spider when a fly flew into the smaller female’s web. I had no idea they could move that fast. She surprised me so badly, I almost tripped over a tree root. That would have been bad considering I was surrounded by spider webs and their owners.
Those of you who read my blog on the little yellow spider, know that an orb-weaver is a spider that spins a spiral, wheel-shaped web like the ones we’re accustomed to seeing in Halloween decorations. Their webs are often found in gardens, fields, and forests. The Golden Silk Spider tends to build its web in the shade under trees. I have to watch for them when I’m walking at the edge of the woods, or I walk into them – an event that neither the spider nor I appreciate.
There are several common names for this spider: golden silk orb-weaver, banana spider, calico spider, giant wood spider, and writing spider. It’s native to the warmer parts of the American continent, and it tends to like forests and coastal woodlands.
“Nephila clavipes is the only species of the genus occurring in the Western Hemisphere. It occurs throughout Florida, the West Indies, as far north as North Carolina, across the Gulf States, through Central America, and into South America as far south as Argentina. Oher even larger relatives occur in the South Pacific, Southeast Asia, and Madagascar.” (H.V. Weems, 2014)
The larger female in the cathedral had a male spider visiting her web. As you can see from the picture, the females are much larger and more colorful than the males. In fact, if we weren’t seeing them together, we might not even recognize them as being the same species. This striking difference between the sexes is called sexual dimorphism.
“Females range from 24mm to 40mm in length. The female color pattern, consisting of silvery carapace, yellow spots on a dull orange to tan cylindrical body, brown and orange banded legs, plus the hair brushes (gaiters) on the tibial segment of legs, I, II, and IV, make this spider one of the most easily recognized. The males, on the other hand, are rather inconspicuous dark brown, slender spiders averaging 6 mm in length which would often go unnoticed if not for the fact that they are often found in the webs of females.” (H.V. Weems, 2014)
“When the male approaches the female for copulation, he stimulates her by vibrating his abdomen using a plucking motion. This activity varies depending on the age of the female and the arousal also prevents the male from becoming a meal. However, female predation on males is not a common occurrence in N. clavipes. …” (Hawkinson, n.d.)
Once the male spider has done his work, the female spins at least two large (about an inch in diameter) egg sacs on a tree. Each one contains hundreds of eggs and is surrounded by a basket of curly yellow silk.
“Banana spiders go through many molting stages, but the most notable is the last stage. Approximately 4 days before a female reaches her final molt, she ceases eating and doing any web repair. Around this time, a mature dominant male will move into her web and spend a few days getting to know her. He is waiting for her to finish molting, because the female is only sexually receptive for 48 hours after this last stage has occurred.” (Hawkinson, n.d.)
I searched the oak tree for the egg sacks, but I didn’t find any. Perhaps the large female hasn’t molted for the final time yet.
They are aggressive predators, but not towards me. They eat flying insects ranging from small flies and mosquitoes to larger cicadas and locusts. Occasionally, because of their strong web structure, small birds and bats are trapped and fed upon. When the spider captures a small insect like a fly, they simply wrap it loosely in silk and take it back to the center of the web. If the prey is large, they bite it to incapacitate it before wrapping it.
All spiders are venomous, including the Golden Silk Spider, but their venom is not harmful to most humans or pets. They are shy, and they really don’t want to bite you. They only bite humans if we pick them up and squeeze them.
“The venom of the golden silk orb-weaver is potent but not lethal to humans. It has a neurotoxic effect similar to that of the black widow spider; however, its venom is not nearly as powerful. The bite causes local pain, redness, and blisters that normally disappear within a 24-hour period. In rare cases, it might trigger allergic reactions and result in respiratory troubles (in asthmatics) or fast-acting involuntary muscle cramps. As the genus possesses relatively strong chelicerae [pincer like claws in the front of the mouth], the bite could leave a scar on hard tissue (such as fingers).” (Golden silk orb-weaver, 2017)
It’s a good thing I didn’t read that until after I visited the web cathedral, or I might not have had the nerve to climb in there. That would have been bad. I would have missed out on an exciting experience and some cool pictures.
The most remarkable thing about the Golden Web Spider is their web. I have seen webs so yellow they looked like they were solid gold. You can’t see that in my pictures, except slightly in the picture of the spider attacking the fly. Perhaps it is the lighting or the time in the spider’s life, but their golden web has entranced humans for centuries.
“The strong web of banana spiders is complex. It is a fine-meshed orb suspended in a maze of non-sticky barrier webs. They make big webs, about 3 feet wide, spun in a place best suited to take advantage of the flight paths of other insects. Some scientists suggest that the silk’s color serves a dual purpose: sunlit webs ensnare bees that are attracted to the bright yellow strands and in shady spots, the yellow blends in with background foliage, acting as camouflage.” (Hawkinson, n.d.)
“There have been several efforts in the past to produce garments from Nephila silk although none commercially viable. These include two bed hangings that were shown at the 1900 Paris Exhibition. In 2004 a textile designer, Simon Peers, and an entrepreneur, Nicholas Godley, managed in three years work and using 1.2 million Golden silk orb-weavers (collected in the wild and released some 30 minutes later after they produced the silk) to produce a shawl that was exhibited at the American Museum of Natural History in 2009. By 2012 they managed to produce a second, bigger garment, a cape, that, together with the shawl, were exhibited at the Victoria and Albert Museum in London.” (Golden silk orb-weaver, 2017)
I’ve seen pictures of the cape. It looks like it's made out of gold, but I’m glad it’s not commercially viable because they fasten the spiders into some sort of frame while spinning and coil the silk up on a spool. It goes on until the spider is exhausted. Yuck!
There are other experiments going on with the Golden Silk Spider web.
“Banana spiders are really wonderful creatures. Their dragline thread (the silk) is of particular benefit to us as they weave strong webs compared to some other spiders. Currently, there are tests being done on their silk as it surpasses the strength of Kevlar, a fiber used in bulletproof vests.
The dragline thread is biodegradable, stronger than steel (with a tensile strength of 4109 N/m, exceeding that of steel by a factor of six) and is economically valuable. Recently, the silk has been used to help in mammalian neuronal regeneration for the body’s immune system does not recognize it and the silk has antibacterial properties.” (Hawkinson, n.d.)
But, it isn’t just scientists that think the Nephila is useful. Fishermen on the coasts of the Indo-Pacific Ocean use the webs to catch baitfish. South Pacific natives eat the pregnant females as a protein supplement. The resources I found say they have a consistency of raw potatoes and lettuce with a nutty flavor like peanut butter, but stickier. Yuck again!
The Golden Silk spiders at my house are safe. I’m not going to steal their web or eat them. I’m just going to take their pictures. If you happen to live in the Golden Silk Spider's range, find some woods and check under the trees. Maybe you’ll get lucky and have an opportunity to take pictures of your own.
Barlett, T. (2004, Feb 16). Golden Silk Orb-weaver. Retrieved from Bugguide: http://bugguide.net/node/view/2023
Golden silk orb-weaver. (2017, July 30). Retrieved from Wikipedia: https://en.wikipedia.org/wiki/Golden_silk_orb-weaver
H.V. Weems, J. a. (2014, Feb). Golden Silk Spider - Nephila clavipes. Retrieved from Department of Agriculture and Consumer Services, Division of Plant Industry: http://entnemdept.ufl.edu/creatures/misc/golden_silk_spider.htm
Hawkinson, C. (n.d.). Banana Spider. Retrieved from Galveston County Master Gardners, Beneficials in the Garden: http://aggie-horticulture.tamu.edu/galveston/beneficials/beneficial-49_banana_spider.htm