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Recluse spider (Family Loxoscelidae, Loxosceles species) adult male This Report: 19 August 2007---Wichita Falls, Texas Reports and photographs sent in by Ralph E., Editing and notes by Jerry Cates a.k.a."Brown recluse spider" (click on the link for a definition)
Ralph E. Wrote: Hello---We have just moved to Texas. We are a bit concerned, as we constantly find spiders in and around our pool and in our kitchen. We have attached some photographs (Editor's comment: the photo and its enlargement, shown on this page, were taken in the correspondent's kitchen). Could you please help us identify them? Are they poisonous or dangerous? How can we get rid of them? Thanks and best regards---Ralph E. Question: How dangerous is the bite of a recluse spider? Ed. notes: Many recluse spider misidentifications occur annually throughout the United States because the investigator failed to examine the specimen's eyes under magnification, and/or they failed to take into account other features of the spider's anatomy. Some non-recluse spiders resemble them superficially, being brown in color with markings on their "backs" (technically, their carapaces) in the generalized shape of a fiddle or violin (see, for example, the southern house spider [Kukulcania hibernalis]). The quality of Ralph's photograph does not permit an examination of the eyes (note that an enlargement of the carapace, below, fails to resolve any eye details). Still, other anatomical features suggest that this is, indeed, a recluse spider. Dr. Rick Vetter, an entomologist at the University of California, Riverside, cites four anatomical features that may be used to identify a recluse spider: (1) six eyes in three pairs that face forward, left, and right; (2) the head near the eyes is dark in color; (3) the abdomen is tan or brown, with no markings; (4) the legs have no spines. Our specimen clearly meets three of these four. Furthermore, the carapace of a recluse spider is generally flat, with a prominent anterior protuberance for the head, bordered on each side by a vague cephalic groove whose posterior juncture meets at a well-defined, longitudinal thoracic groove that extends thence to the posterior margin of the thorax. The cephalic protuberance of a recluse spider is also marked with a series of longitudinal lines. Any spider with these features, and the last three of the four features cited by Dr. Vetter is, as in the case of our present specimen, almost certainly a recluse spider.
Note that the pedipalps (the short leg-like structures projecting forward, from each side of the head) of this specimen are swollen at their ends. The female's pedipalps are slender, without enlarged ends, but those of the male have this appearance due to the presence of specialized structures in the palps that are used to transfer sperm during mating. Ralph asked how to get rid of these spiders. The answer is somewhat complicated by spider biology. Spiders are not as susceptible to residual pesticides as insects are, because they feed mostly on live prey (vs. dead ones killed by and therefore contaminated with pesticides). Spiders also do not come into gross contact with surfaces in their environment where residual pesticides repose. Dr. Michael Merchant, extension entomologist with the Texas Department of Agriculture, suggests control procedures in a tract he authored for the Texas Agricultural Extension Service. This tract was reviewed by Dr. John A. Jackman, a published arachnologist at Texas A&M University, so we might say it comes highly recommended. No traditional pest management chemicals or toxicants are known to be effective against recluse spider infestations in residences. For that reason, I strongly suggest that anyone with such an infestation focus first on cleaning and de-cluttering the affected premises, and then consider using alternative, least-toxic products and methods to eliminate the spiders altogether. Many thanks to Ralph E. for sending in this excellent photograph. ---------------------------------------------- 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: Recluse Spiders * Texas Spiders Back to: Bugsinthenews |
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