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The Common Southern House Spider Produces Venom That Contains Proteins Found In Brown Recluse Venom

Kukulcania hibernalis, or the “southern house spider, may be the most frequently encountered spider species within homes located in the southern US states, with the possible exception of cobweb spiders. According to an online survey, of the 120 separate southern house spider sightings documented by citizen scientists, 98 occurred indoors, and most of the remaining 22 sightings occurred near homes. These spiders commonly nestle into crevices on the exterior walls of homes before covering the crevice with their silk webbing for shelter. Adult males are brown in color and can grow to half an inch in length, not counting leg span, while black females can grow to be ¾ of an inch in length, making these spiders relatively large in size.

Southern house spiders are very common in all structures in Arizona, but particularly older structures. The are also somewhat similar to brown recluse spiders in appearance, but southern house spiders are generally dismissed as being largely harmless to humans. However, recent research suggests that the venom produced by these common spiders may be more toxic to humans than previously thought, and many experts believe that a large number of brown recluse bites documented in the past may have been misdiagnosed southern house spider bites.

One of the first studies to find similarities between southern house spider venom and brown recluse venom was carried out in 2002 when researchers were working to find a treatment for tissue necrosis caused by brown recluse bites. The study compared venoms produced by several different spider species, and it turned out that the venom of southern house spiders shared a significant number of proteins found in brown recluse venom. Today, many researchers believe that the southern house spider is responsible for inflicting bites that induce tissue necrosis around the wound. Southern house spiders invade homes in Arizona all year round, and their indoor presence can be recognized by webs in corners and largely uninhabited areas within homes. They are most frequently found hidden behind and underneath furniture, crawl spaces, attics, garages and basements. Despite recent findings concerning southern house spider venom, they are very rarely responsible for inflicting harmful bites, and are not nearly as dangerous as brown recluse spiders.

Have you ever found what you believed were southern house spiders in your home?

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