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Golden silk orbweaver (Nephila clavipes) adult female Report and Photographs Courtesy of Sandra R., Houston, Texas, 12 July 2007 Editor's Notes by Jerry Cates
Sandra Wrote: Jerry---Look what I found in my back yard in Houston, Texas!
Editor's Notes: The above photo is of the orb web, with the spider at its central hub. The photo below is an enlargement of the spider itself (note the tufts of black hairs on the legs, which are definitive for this species of orbweaver in the U.S.; the rectangular marking in the middle of the ventral abdomen is also definitive insofar as it differs from ventral abdominal markings found on members of spiders in the genus Neoscona). The golden silk orbweaver (Nephila clavipes) is relatively large at maturity, and occurs in the southeastern U.S., from as far north as North Carolina, southward to Florida, and westward to Texas. Unlike the yellow garden spider (Argiope aurantia) which is found readily throughout much of its range, the golden silk orbweaver forms localized concentrations, especially near swampland or forested coastal regions, and is absent over much of its geographic range where conditions are not so favorable for its development. I have searched much of inland Texas for this species with very little success.
Nephila clavipes is a member of the Nephilidae family (until 2006, they were grouped under the Araneidae and Tetragnathidae). This family, known as large-jawed spiders, is presently divided into four genera of 75 species worldwide. They partially renew their webs, usually a section at a time, rather than performing a total dismantling and rebuilding as with many other spiders (e.g., Argiope spp.). They also abandon their old webs from time to time, to the temporary dismay of arachnology students observing their development. I say temporary, because they and their new web can usually be found close by the old one, after a bit of sleuthing. Such habits (both partial renewal and abandonment) are sometimes done in response to the presence of kleptoparasitic spiders in the genus Argyrodes who collect around orb webs to steal captured prey.
Nephilidae webs are unusually complex, though the full extent of that complexity is not immediately obvious. The unaware observer typically notices only the brighter, more obvious sticky spirals, not discerning the numerous non-sticky, less visible spirals between them. Indeed, the latter are so fine that they do not show on Sandra's photos (see the photo below). When spiders of other genera spin their webs, the non-sticky spirals (spun first upon a foundation of radial strands) are removed as the sticky spirals are spun afterward. The Nephila leave the non-sticky spirals in place, producing what appears, to those with good eyes and attention to detail, something analogous to the template for a musical score, awaiting a musician to add the notes of a great symphony. Conjure in your mind the sweet strains of a Brahms concerto, or perhaps a jaunty spate of Mozart, writ upon such a web... Then visualize the 40-hertz oscillations of an agitated Nephila clavipes, responding to the stimulation of its web by an intruder. Arachnology in motion. Beautiful... But I digress.
My Reply to Sandra: When I replied to Sandra's message containing these photos, I could not hide my excitement. This species has been of great interest to me for some time, and I'd hoped to receive some good photos of it before long. Of course, I begged her to take more, especially of the dorsal abdomen and carapace, and--if possible--the eyes. ---------------------------------------------- Please contact us about your personal experiences, if you have been bitten by a brown recluse, black widow, or any other spider, including jumping spiders and garden spiders (the bites of which typically produce a transitory inflammation, but resolve within a few days without medical attention), whether recently or in the past thirty years, anywhere in the world. For example, the bite of a species of garden spider, the golden orb spider of Australia [Nephila edulis] typically is unremarkable, but on occasion produces medically significant secondary infections; the frequency and nature of bites experienced from that species of spider is also a part of this study. One object of this study is to collect data that might relate to a mysterious series of spider-related infections, involving a special pathogen, that took place in the United States and in Australia between 1977 and 2006. Although only fifteen such infections were reported to medical establishments, seven appear to be associated with spider bites. Some authorities suggest that the number of actual infections of this type that occurred in the U.S. and Australia during the past thirty years is much larger, but that they have been underreported. Underreporting of specific kinds of infections can occur, either because the persons infected chose not to seek medical assistance, or the medical establishments misdiagnosed the infections as being caused by other infectious agents. We are seeking to establish an estimate of the number of human spider bites that occur each year by these and similar spiders, whether the bite resulted in injury to the human or not. Next, we hope to establish the number of instances where the bite (1) became inflamed and/or infected, then resolved without medical intervention, or (2) infected, ulcerated, or led to a generalized sickness, and required medical intervention. ---------------------------------------------- Back to: Texas Spiders Back to: Bugsinthenews |
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