Nephila clavipes

Nephila clavipes
Female, Jamaica
Male, Jamaica
Scientific classification
Kingdom:	Animalia
Phylum:	Arthropoda
Class:	Arachnida
Order:	Araneae
Suborder:	Araneomorphae
Family:	Nephilidae
Genus:	Nephila
Species:	N. clavipes
Binomial name
Nephila clavipes (Linnaeus, 1767)
Synonyms
Aranea clavipes Aranea spinimobilis Aranea longimana Epeira clavipes Epeira plumipes Nephila wilderi Nephila wistariana Nephila concolor Nephila thomensis

Nephila clavipes is the only species of golden orb-web spider indigenous to continental North and South America. In the United States it is commonly known as the "banana spider".

Physical attributes

Nephila clavipes has the large size and the long legs with clumps of hair that are typical of the genus. It is large compared to most other members of the genus, and is distinguished by the bright colours of the female abdomen, which changes colour as the spider matures.

As is usual among orb-weavers, there is marked sexual dimorphism in general appearance, but especially in size; in linear measurements males are three to four times smaller than females, and they also are more slenderly built. This implies a mass some thirty to seventy times smaller than that of a large female.

Female ventral side, Jamaica

Etymology

The specific epithet clavipes is derived from the Latin:

• clava, that variously may mean "knotted staff", "club", or "key"; and
• pēs meaning "of or pertaining to a foot".^[1]
  In assigning the name, Linnaeus apparently referred to the clumps of hair on the legs.

Distribution and transport

Nephila clavipes occurs most commonly in the Antilles and in Central America from Mexico in the north through Panama in the south. Less abundantly it occurs as far south as Argentina and in the north it occurs in parts of the southern states of the continental USA. Seasonally it may range more widely; in summer it may be found as far north as lower Eastern Canada. Beyond 40° N latitude these spiders seldom survive the winter.

Because humans inadvertently transport spiders as passengers in cargo containers, plant nursery stock and the like, Nephila clavipes generally occurs very unevenly over wide areas; often there are patches of high local densities 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.

The main web of a mature female may be as large as one meter in diameter, not counting the main filaments that anchor the web between trees; such anchor filaments may be two or three meters in length. A yellow pigment in the silk lends it a rich golden glow in suitable lighting. Males come into the female's web for copulation and mate with her while she is feeding and unable to attack them. After mating, the female spins an egg sac on a tree, laying hundreds of eggs in each sac.

Significance to humans

The spider is not aggressive and only bites if pinched; the venom is relatively harmless and rarely causes more than slight redness and temporary localized pain.^[2]

A single thread of the anchor silk has a tensile strength of 4×10⁹ N/m², which exceeds that of steel by a factor of eight (Ultimate strength of steel 500x10⁶ N/m²).

The silk of Nephila 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. Best of all for these experiments, the silk elicits no reaction from the immune system, and thereby escapes rejection by the host body.^[3]

Footnotes

1. Jaeger, Edmund Carroll (1959). A source-book of biological names and terms. Springfield, Ill: Thomas. ISBN 0-398-06179-3.
2. Weems, Jr., H.V., and G.B. Edwards, Jr. 2001
3. Allmeling et al. 2006

References

• 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. PDF - doi:10.1111/j.1582-4934.2006.tb00436.x
• Borror, D. J. 1960. Dictionary of Word Roots and Combining Forms. Mayfield Publishing Company, 134 pp.
• Cameron, H. D. 2005. Chapter 73 — An etymological dictionary of North American spider genus names, page 73 in D. Ubick, P. Paquin, P.E. Cushing, and V. Roth (eds.) Spiders of North America: an identification manual. American Arachnological Society, Keene (New Hampshire).
• Weems, Jr., H.V., and G.B. Edwards, Jr. 2001 (2004 revision). golden silk spider. on the UF / IFAS Featured Creatures Web site

External links

• Mating pair
• Pictures of N. clavipes (free for noncommercial use)
• Gravity favours smaller males : Review of scientific article on why males are much smaller than females