Spider Bite

Diagnosis 

Latrodectus geometricus (brown widow spider) bite Five species of Latrodectus are found in the United States.1 Three of these (L. mactans, L. hesperus, and L. variolus) are called black widow spiders, characterized by uniformly black bodies except for a red-orange ventral marking often resembling an hourglass. The red widow spider, L. bishopi, is found in Florida. Latrodectus geometricus (Figure 3), the brown widow spider, is a recently introduced species whose range in the United States is increasing.1, 2 L. geometricus was first described in 1841 in South America and southern Africa, but its range has since spread. In North America, the brown widow had historically been limited to peninsular Florida.1 Since 1980, reports have documented the brown widow's appearance in Hawaii, Japan, southern California, and Australia, associated with human activities and shipments of goods.2 Within the United States, the brown widow spider has spread throughout Florida, into Georgia, South Carolina, and along the coast into Louisiana (first found in 2002), Mississippi (2005), and Texas (2007).1

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Figure 3. Latrodectus geometricus, the brown widow spider, crawling on a concrete wall. Another specimen collected in Orange County, CA, October 2008.

Brown widow spider bites tend to be less serious than those from black widows. Mild local symptoms were typical in a series of 15 brown widow spider bites in South Africa.3 Among 3 brown widow bites in Florida, only 1 patient's reaction was rated severe.1 The treating physician in the current case first assumed the spider was an immature L. hesperus, the indigenous black widow (Figure 4). The spider was later positively identified as Latrodectus geometricus by an arachnologist (R. Vetter, written communication, April 2007). Physicians should not rule out the potential for systemic latrodectism solely according to the spider's lack of typical black widow markings. Serious envenomations by the brown widow would be treated identically as for black widow spider bites.

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Figure 4. Comparative view of an indigenous black widow spider (Latrodectus hesperus; left), the spider depicted in Figure 3 (middle), and the index spider (right; colors faded from preservation in rubbing alcohol). Because of its relatively small size, the black widow specimen is probably immature, yet still has the normal adult markings. Used with permission of Jeffrey R. Suchard, MD, Department of Emergency Medicine, University of California, Irvine Medical Center, Orange, CA.