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Arabesque Orbweaver (Neoscona arabesca) Report and Photograph Courtesy of Kathleen W., Houston, Texas, June 3, 2007 Additional Notes by Jerry Cates
Kathleen Wrote: Jerry--I have a bunch of photos of this spider to send you. Some are a little blurry, but I couldn't bear to delete them. Let me know which one(s) you like! I'll be sending 10 photos in all, probably in a few batches. I took these last night, the 2nd of June, at about 11pm, in the West Memorial area of Houston-- Kathleen
My Reply: Kathleen---Beautiful photos! This is, methinks, the arabesque orbweaver (Neoscona arabesca), one species in a genus that contains what we might call "workhorse" orbweavers--the ones that are not quite as showy as, say, the yellow garden spider (Argiope aurantia), but that are so numerous in our croplands and forests that the work they do in killing pesky flying insects makes them unusually valuable. Some authorities have estimated that in certain locales these and similar spiders are present in numbers of up to 2,000,000 spiders per acre. That's about 43 spiders per square foot. Obviously, that could only happen in three dimensional space, with considerable vertical habitat. Notice the markings on the dorsal abdomen in the above photo. The arabesque orbweaver has generally three pairs of dark markings that form "commas" whose thickest portions are near the midline; the commas then stretch laterally outward, pointing slightly forward toward the head. At the median anterior dorsum of the abdomen are four spots that form a trapezoid, with a pale border on each lateral margin.
Underneath this orbweaver's abdomen is a square-shaped marking outlined on the sides and at its anterior margin in pale yellow, with a dark center that extends to the entire posterior edge and the central fourth of the anterior edge, that is shaped like a vase--with a narrow anterior neck, a broad center, and a broad posterior base. This square marking, in its generalized format, is probably present with most spiders in the genus Neoscona, but the shape of the dark central mark varies from one species to another. Some authorities indicate that the same marking is also present in members of the genus Araneus, though it is clearly not present in the giant lichen orbweaver (Araneus bicentenarius), and that the only gross anatomical distinction between the genre Neoscona and Araneus is the presence, on the posterior carapace, of a transverse thoracic groove in the genus Araneus vs. a longitudinal groove in the genus Neoscona. Unfortunately, the structure of the thoracic groove is often obscured by the abdomen or by the hairs of the carapace. In Kathleen's photos, only the photo below shows the portion of the carapace where the thoracic groove lies. Inasmuch as this photo is slightly out of focus, the architecture of the groove is in doubt.
The eight eyes of spiders in the genus Neoscona are almost equal in size, and form an ellipse that is flattened vertically and stretched horizontally. Four eyes are in the center of the face, with two on top, and two on bottom. The two largest (the posterior median eyes, or PME) are on top, and are closer together than the two below them (the anterior median eyes, or AME). On each lateral face are two smaller eyes, the upper of which is designated the posterior lateral eye (PLE), while the lower is the anterior lateral eye (ALE). Additional Notes Kathleen's original photos were superb, and could be enlarged without losing detail. I'm looking forward to more photos from this outstanding photographer. ---------------------------------------------- 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. ---------------------------------------------- Back to: Texas Spiders Back to: Bugsinthenews |
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