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Common name: Golden Orb-Weaver
Latin name: Nephila Clavipes
Family: Nephilidae

Range and Abundance:
It is found throughout Florida, up to North Carolina, throughout the West Indies down through Central America and as far south in South America as Argentina. It is most abundant in Central America and the tropical regions of South America. N. clavipes is the only member of its genus found in the Western Hemisphere.

Coloration and Morphology:
N. clavipes is characterized by dramatic sexual dimorphism. The female is by far the more impressive sex, reaching sizes of between 24-40 mm long, not including legspan. Females have a typical beautiful color pattern, with a metallic silvery carapace, and golden spots on a tan body. The long legs are black and orange, with feather brushes called “gaiters” on the tibial segment of legs. Males, by contrast, are very small and rather drab dark brown in coloration, averaging a mere 6 mm in length. There are conjectures that the color patterns serve as a warning against predators to suggest possible venom.

Reproductive cycle:
N. clavipes has a maximum life span of about 1 year in the wild. Eggs are laid during October and November, which is the rainy season in Costa Rica. The eggs are wrapped in protective silk and are initially cemented very tightly together, although they begin to separate as hatching approaches. The eggs are usually laid on a thin branch near the mother’s web site. The eggs hatch 1 month after deposition, although the spiderlings remain in the silk egg case until May or June. When they emerge from the egg case they linger for about 1 week near the mother’s web before dispersing via ballooning or simple terrestrial travel. After 1 week, the first molt occurs. It takes about 6-7 molts for the spiders to reach maturity. Males visit the webs of females to mate, and, unlike with many species of spiders, the male is not eaten or harmed in the process.

Habitat:
The literature reports the habitat as being marshy, open areas in forests, usually with the webs slung between trees and shrubs. The spiders are tremendously adaptable with respect to their environment; they have been observed building webs on telephone poles and even between the supports of suspension bridges. Spiders build their webs at all different heights, although rarely at ground level, presumably because the danger is too great there that a large mammal will walk through the web and destroy it. Spiders tend to prefer light shade to moderate sunlight, although they can tolerate full sunlight. They must live in tropical climates, as if their body temperature falls below 10 C, they become inactive and die quickly.

Ecology:
N. clavipes cannot build their webs too close together, for larger females will build larger webs which out-compete smaller females’ webs for prey capture. For this reason N. clavipes needs a considerable tract of land to form a thriving population. Also, N. clavipes tends to build its web in places where it is unlikely to be destroyed by terrestrial disturbances. The reason for this is that the spiders invest a tremendous amount of energy in spinning their webs, and these webs are the only mechanism by which they can attain more energy via prey capture. Webs are always built off of trails and several feet off the ground, well above the range where a peccary (the most likely offender) would be able to walk through the web. Populations tend to have a close to 1:1 ratio of males to females, and when the number of males increases, competition occurs between males and only a few are able to mate.

Behavior:
The name “Golden orb-weaver” refers to the color of the spider’s silk, which is gold because of the presence of xanthurenic acid, two quinones and a fourth compound that has yet to be discovered. The golden web likely aids in prey capture because it makes it difficult for prey to see in sunlight, and the spiders are able to modulate the amount of pigmented compound present in the web based on their location. The females occasionally share support threads of their webs to build vast networks. However, the animals are not social creatures and typically this is just a phenomenon that arises when the population density is extremely high. They are sit-and-wait predators like all orb-weaving spiders, and detect the presence of prey in their nest by vibrations along the threads of their webs.

Diet:
Golden orb-weavers eat mainly other insects, especially butterflies and dragonflies, although they have been known to eat small birds and even lizards and snakes. This is not surprising; the tensile strength of their webs is 4 x 109 N/m2, which exceeds that of steel by a factor of six. The web has a feel that is very similar to fishing line. If a human got tangled in it, it would be difficult for him to get out, let alone a tiny anole or hummingbird.

Interactions:
N. clavipes are frequently the hosts of a kleptoparasitic genus of spiders called Argyrodes, which live in the female orb weaver’s nest and steal her captured prey. The golden orb-weaver frequently rebuilds her nest, which some scientists suggest might be a defense mechanism against inhabitation by Argyrodes.
At one point, the golden orb-weaver’s web was used to spin silk, but this was an economically inefficient process in the long term and does not happen often anymore. Fishermen have actually used N. clavipes webs to catch fish, like a net. A new interaction with humans that is promising to the realm of neurobiology is the use of golden orb-weaver webs in tissue engineering. The web is not targeted by the immune system and its great mechanical strength help it promote cell proliferation and adhesion. It is most promising for the field of neuronal regeneration, because it is a scaffold and a guide for peripheral nerve regrowth. People call these spiders nightmarish, but they are magnificent, harmless, and could improve the quality of life of thousands of people.

Personal Experience:
N. clavipes is very abundant around La Selva and even along the roadways on the way to Manzanillo National Park. They have very little fear of humans and will readily build their webs in areas with high levels of human traffic, including on a suspension bridge. Most of the time I observed them sitting in the middle of their webs. A few of the webs had tiny males in them; more than one per web was never observed.


References:
The Life Cycle, Habitat and Variation in Selected Web Parameters in the Spider, Nephila clavipes Koch (Araneidae)
Clovis W. Moore
American Midland Naturalist , Vol. 98, No. 1 (Jul., 1977), pp. 95-108

http://search.engrant.com/project/0AxXNR/the_nutritional_ecology_of_the_web_of_nephila_clavipes

Farr, J. A. Social behavior of the golden silk spider Nephila clavipes. 1997. J. Arachnol. 4: 137-144

Allmeling, C.; Jokuszies, A.; Reimers, K.; Kall, S. & Vogt, P.M. (2006): Use of spider silk fibres as an innovative material in a biocompatible artificial nerve conduit. J. Cell. Mol. Med. 10(3): 770-777.