Loxosceles reclusa occupies a well-mapped block of the central and south-central United States. Reported bites do not follow that map. Surveys by the arachnologist Richard Vetter collected large numbers of diagnoses from states such as California and Florida, while requests for specimens returned other spiders, insects or nothing.
The converse case is equally instructive. A Kansas family home yielded more than two thousand recluses collected over six months, with no bites to the people living in it. Recluses are retiring animals that bite when pressed against skin.
The venom is real. Sphingomyelinase D can destroy tissue around the bite, producing the sunken necrotic lesion the species is known for, though most bites resolve without it. Many lesions attributed to recluses turn out to be something else, most often bacterial infection including MRSA, but also vascular ulcers, burns and fungal disease that respond to entirely different treatment.