|Description:||Magnified 88X, this scanning electron microscopic (SEM) image depicted the distal end (farthest from attachment to the body) of a “hair”-covered leg of a venomous brown recluse spider, Loxosceles reclusa, found inhabiting a Kentucky farm. The hairs are known as “setae”, and for the most part are sensorial in nature, providing the spider with information about the organism’s environment such as temperature changes, changes in wind direction, and chemical queues such as poisons or pheromones. Note the very small cluster of setae at the location of the metatarsotarsal joint. These may be involved in the act of web weaving, but this is only speculation. See PHIL 10093 for a higher magnification of this specialized region. L. reclusa is sometimes referred to as the “violin” or “fiddle” spider, for on its cephalothorax, i.e., a combination of its head and thoracic regions, one will see what appears to be coloration in the shape of these stringed instruments (see PHIL 1125).|
Although spider bites are common in many parts of the United States, most domestic spiders are not substantially venomous to man. The best known exceptions are widow spiders, i.e., Latrodectus spp., including the black widow L. mactans, and brown spiders Loxesceles spp., particularly the brown recluse, Lox. reclusa. However, cases of arachnid envenomation from the hobo spider, Tegenaria agrestis, are being reported increasingly in the Pacific Northwest.
Sometimes a bite from a brown recluse spider can go unnoticed, or maybe feel as slight as a pinprick. However, usually, after 2–8hrs, there is ensuing severe pain, erythema, and localized tissue necrosis due to the venom’s proteolytic enzymes. See PHIL 6265, and 6266 for images showing the after affects of a L. reclusa bite.