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Dark fishing spider (Dolomedes tenebrosus), Porter, Texas Report and Photographs Courtesy of Greg S., Porter, Texas, 3 July 2007 Editor's Notes by Jerry Cates
Greg Wrote: Jerry--I found this spider in Porter Texas, on my back patio on the wall, at night, on July 3rd 2007. It didn't move or try to escape. Its body is about 1 1/2 inches long, and when including the legs the the whole spider is 4 1/2 inches in diameter. My camera had trouble focusing close enough for the eyes, but it has two rows of eight eyes, the top (posterior) row being larger, and the bottom (anterior row) small and bunched together. I Identified it using the information posted at http://entomology.uark.edu/museum/dolomede.html. I can't tell whether it is tenebrosus or scriptus. Anyway, thought you might be interested--Thanks, Greg.
Editor's Notes: The dark fishing spider (Dolomedes tenebrosus) is a large spider, found in the eastern half of the U.S. and Canada, from New England and adjacent portions of southeastern Canada, south to Florida, and west to South Dakota and Texas. It and others in the genus Dolomedes generally live near water, and feed primarily on aquatic insects. However, they will also prey on terrestrial insects and will also capture and feed on small fishes and other small aquatic organisms. This spider is a member of the Pisauridae family, known as nursery web spiders (they do not build a silk snare, but hunt as in the Lycosidae; the female carries an egg sac under the sternum until just prior to spiderling emergence, whereupon she builds a nursery web around the sac and guards it until the spiderlings have emerged). At least 52 genera, and 328 species are recognized worldwide. At least five genera are recognized in North America, with Dolomedes occupying a prominent position in the extant literature. This genus includes nine species in North America, including D. scriptus (no recognized common name, but perhaps the light colored fishing spider is most appropriate), D. tenebrosus (the dark fishing spider, being darker than D. scriptus and lacking its prominent white markings, having similar, but subdued markings instead), D. triton, previously known as D. sexpunctatus (the six spotted fishing spider, so named for the two rows of six spots on the lateral margins of the abdomen), and D. vittatus (a fishing spider with no common name and little uniqueness to its markings to commend one, though the pattern of the triangular dark spots forward of the thoracic groove is distinctive, being larger and more prominent than in most Dolomedes) . A close cousin to the Dolomedes is the genus Tinus, which contains one species (Tinus peregrinus). Slightly more removed are the four species of the genus Pisaurina. As Greg pointed out, the differences between Dolomees scriptus and D. tenebrosus are not easy to distinguish, and my skills are certainly no better than his. I base my suspicion that this is D. tenebrosus on the absence of large white areas on the dorsum, and on the absence of white "W" markings on the dorsal abdomen. In D. scriptus, the white "W" markings are of a uniform albedo throughout, from right to left across the dorsal abdomen, while in D. tenebrosus they are replaced by light-gray chevrons flanked with white spots of a lighter shade of gray. It is possible that additional photos of this same spider, from other angles under different lighting, would lead to another conclusion. All the fishing spiders are considered beneficial, as they keep insect populations down within their spheres of influence. Their bites are not particularly troublesome.
My Reply: Greg--Good photos. Thanks. If you still have this guy around, consider taking additional photos, particularly of the dorsal abdomen, and of the eyes. Consider using a flash, to bring out subtle features of the dorsofrontal head---Jerry ---------------------------------------------- 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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