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Yellow garden spider (Argiope aurantia) by Jerry Cates
While in San Antonio on July 26, 2002, I took these photos of a large female Argiope aurantia spider. This specimen, measuring an estimated 4 inches from the tip of the left rear leg to the tip of the right front leg, was one of the largest I've found in Texas. The largest, spanning more than 5 inches, was observed at a roadside park on U.S. Highway 77, between Lott and Cameron, in 1993. If you compare this spider with the one photographed in Round Rock in 2001 (An Argiope species) you will notice, besides many similarities, several important differences. Besides their radically different sizes, the spider shown here has a carapace (the part of the body where the legs attach) that is covered with silvery gray hairs. The legs of this spider are black along their lengths except for the segment nearest the carapace (the femurs for legs 2, 3, and 4), whose mid-section is yellow. Notice also that the abdomen (the part of the body behind the carapace) has a noticeable hump that makes it higher than the carapace. Each of these features differs in the spider photographed in Round Rock last year, yet both are the same species. The one in Round Rock was immature, but this one is sexually mature, and in the final molt to sexual maturity many important changes occur.
Several people have e-mailed me with questions about yellow garden spiders. The most common question: Is the venom of this spider dangerous to people? This spider is so big that it is natural to worry that it might bite you or your children and cause serious harm. Extant scientific literature suggests that the venom of this spider is very potent to insects. In fact, at least one commercial concern has studied ways to use Argiope venom as an insecticide. That project was placed on hold, however, because insects would eventually become immune to the venom if it was used extensively for insecticidal purposes, and the consequences to this and other spiders whose venom is similar cannot be predicted with certainty. Apparently, the venom is almost harmless to humans, but this spider is known to bite if it is handled roughly. Important Notice We are investigating the risk of secondary infections that may occur as a result of bites from this and other, otherwise harmless spiders whose venom is known to pose little or no danger to humans. In the process, we are collecting information on experiences persons have had with such spider bites. Please contact us about your personal experiences, if you have been bitten by this 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. The 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. ---------------------------------------------- |
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