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Species of spider native to the Americas

Trichonephila clavipes (formerly known as Nephila clavipes), commonly known as the golden silk orb weaver, golden silk spider, or colloquially banana spider (a name shared with several others), is an orb weaving spider species which inhabits forests and wooded areas ranging from the southern US to Argentina. It is indigenous to both continental North and South America. Known for the golden color of their silk, the large size of their females, and their distinctive red brown and yellow coloring, T. clavipes construct large, asymmetrical circular webs attached to trees and low shrubs in woods to catch small and medium size flying prey, mostly insects. They are excellent web builders, producing and utilizing seven different types of silk, and they subdue their prey by injecting them with venom, as opposed to related species which immobilize their prey by wrapping them in silk first. They are not known to be aggressive towards humans, only biting out of self defense if touched, and their relatively harmless venom has a low toxicity, posing little health concern to healthy human adults. Due to their prevalence in forests, T. clavipes may be encountered by hikers. Like many orb weaver species, T. clavipes shows sexual dimorphism, with females possessing both a larger size and more complex and noticeable coloration. Males of the species do not suffer sexual cannibalism or genital mutilation to the same rate that males of other related species in the subfamily Nephilinae do, making T. clavipes a focus of study into the mating behaviors of spiders. The species shows both monogynous and polygynous mating, with a preference for polygyny in most mating environments. T. clavipes is a well studied species with a high recognized value to humans because of their usefulness in spider silk research. Analysis of the species' genome, the first of the orb weaving spiders to be completely annotated, has revealed 28 unique genes for the proteins comprising spider silk, known as spidroins. Furthermore, the silk of T. clavipes has the potential to aid in surgeries involving the nervous system, a capability which has been demonstrated in past experimental studies.

Like most orb weavers, the species displays marked sexual dimorphism in both size and color pattern. T. clavipes females are some of the largest non tarantula spiders in North America, ranging from 24 mm to 40 mm in length when fully developed. It is possible that they are even the largest orb weaver species indigenous to the United States. Females also have very distinct coloring, making the species relatively easy to recognize. They have a silvery white cephalothorax and a longer orange brown abdomen with two rows of small white yellow spots. The abdomen changes color as the spider matures. Their legs consist of dark yellow and brown banding, and the first, second, and fourth leg pairs also contain black brush like tufts of hair near the joints. Males, meanwhile, are much smaller, about one third to one quarter the size of females at roughly 6 mm in length, and also have a more slender build. Their mass is roughly between 1/30th and 1/70th that of a large female. Male coloration, meanwhile, is much less complex, consisting of a dark brown body and legs. Males' legs contain a black band near the end of the tibial segment, in the same area as where the black hair tufts would be on a female. T. clavipes resemble its congener Trichonephila plumipes in that the females both possess a collection of stiff hair on their legs. However, the hairs of T. plumipes are more closely set together than those of T. clavipes. As a whole, the name means "club footed." Linnaeus, who named the species in 1767, was likely referring to the noticeable tufts of hair on the females' legs, giving them a clubbed or knotted appearance.

According to some scientists, Trichonephila clavipes belongs to the spider family Nephilidae, or golden orb weaving spiders. However, other researchers have done away with the Nephilidae family, instead assigning all golden orb weaving spiders to the subfamily Nephilinae, within the family Araneidae. After the latest phylogenetic studies, the Nephilinae subfamily now contains the genera Nephila, to which T. clavipes originally belonged, and Trichonephila, its current assignment. Of all the Nephilinae genera, Trichonephila is the most species rich genus. Because humans inadvertently transport spiders as passengers in cargo containers, plant nursery stock, and the like, T. clavipes generally occurs very unevenly over wide areas; often, patches of high local densities are found far from any other populations. Accidental human transport of the species increases markedly in late August to early September, when the spiders' reproduction is at its height.

In T. clavipes, males move from web to web, attempting to mate with the female web owners. Males risk death with each move to a new web, largely due to predation, and this mortality risk increases as the breeding season progresses, so that the risk is lower in the early stages of the season and highest in its later stages. As a result, males are more choosy in the early season than they are in the late season.

T. clavipes males may mate just once, monogynously, but are also capable of polygynous mating. Thus, sometimes a male will only have enough sperm for a single mating, forcing the male to invest in a monogynous relationship rather than searching for further mates. There are several factors that play into a male's total mate number, but the ability of T. clavipes males to mate multiply allows males of all sizes to have equivalent mating success. It is thought that as a result, there is relaxed selection on male size in T. clavipes and other similar species. Given its size, the web is easily damaged by large flying bugs, birds, or debris; and needs to be repaired constantly.

There are seven different types of silk glands across the orb weaving spider species, each producing its own type of silk, and T. clavipes females possess all seven of these silk glands.

T. clavipes feed on small flying insects. Webs constructed by this species are used to catch this prey. They can feed on grasshoppers, flies, and other small insects. As the prey is entangled in the strong web, T. clavipes wrap it in silk like a casing.

The spider is not aggressive and only bites if handled roughly; the venom is relatively harmless and rarely causes more than slight redness and temporary localized pain.

T. clavipes has been incredibly useful in the study of spidroins; its spidroins were the first to be characterized, and its genome has been the first of the orb weaving spiders to be annotated, contributing information about 28 unique spidroins.

The silk of T. clavipes has recently been investigated to evaluate its usefulness in surgically improving mammalian neuronal regeneration. In vitro experiments showed that a filament of the silk can lead a severed neuron through the body to the site from which it was severed. The silk elicits no reaction from the immune system, and thereby escapes rejection by the host body.