Recluse spiders (Araneae: Sicariidae): contesting myths on distribution, bite behavior, and medical risk in Florida

Recluse spiders are arachnids of potential medical significant due to their necrotic venom. However, in areas populated by the brown recluse, Loxosceles reclusa, bites and necrosis are rare. In Florida, USA, public media reports and medical case studies have propagated three misconceptions about recluse spiders: breeding populations are widespread in Florida, USA; recluse spiders readily bite when encountered; and verified recluse spider bites inevitably produce necrotic wounds. Here, in onsite investigations of 220 Florida properties with alleged infestations of recluse spiders reported to the USDA or the Florida Brown Recluse Project, we found breeding populations of the invasive Mediterranean recluse (L. rufescens) at only 19 sites. In experimental bite assays including non-injurious pressure or pinching to jaws, legs, or abdomen, brown recluse and Mediterranean spiders exhibited negligible bite responses (median = 0%). In contrast, wolf spiders exhibited significant defensive bite responses (median = 80%). Lastly, only one verified bite was reported by an adult female, which did not result in necrosis. In conclusion, our field survey and behavioral assays challenge three long-standing myths specific to Florida. Recluse spiders are scarce. Recluse spiders are reluctant to bite. Recluse spiders are unlikely to account for most necrotic skin wounds attributed to them. In the final analysis, the risk to humans has been overstated, warranting a reevaluation of their role in suspected necrotic lesions by the medical community and the public.