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1. A genus of venomous brown spiders, marked by a fiddle-shaped pattern on the cephalothorax and a distinct six-eye pattern, found chiefly in South America. They inflict a highly ulcerative, spreading dermal lesion at the site of the bite (loxoscelism). Important species include L. laeta, the Chilean brown recluse spider, also found in Brazil, where L. intermedia and L. gaucho also present important human risk; and L. rufipes, the Peruvian brown spider. In North America, L. reclusus, the brown recluse spider is the most important, occurring across a large portion of the south central midwestern U.S.; L. deserta, L, arizonica, L. apachea, L. blanda, and L. devia also bite humans.