Bites from Loxosceles spiders (brown spiders, recluse spiders or fiddle-back spiders) cause loxoscelism which most commonly causes local necrotic lesions and rarely systemic envenoming. 1, 2 Loxosceles species are widely distributed but only cause a major health issue in South America where the most important species are: L. laeta (wide distribution), L. intermedia (Brazil and Argentina) and L. gaucho (Brazil). Some species occur in other parts of the world, including South Africa, Europe, North America and Mexico (L. reclusa and L. deserta) and South Australia.

Figure 1: Examples of loxosceles bites at different times demonstrating the initial erythema, ecchymoses and then necrosis (Images courtesy Marlene Zannin).

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References
1. Swanson DL, Vetter RS. Bites of brown recluse spiders and suspected necrotic arachnidism. N Engl J Med. 2005; 352(7): 700-7.
2. Isbister GK, Fan HW. Spider bite. Lancet. 2011; 378(9808): 2039-47.