Mediterranean Recluse

Loxosceles rufescens — the Mediterranean recluse — is one of about 140 species in genus Loxosceles (the brown recluse spiders, family Sicariidae) and the most globally invasive recluse spider in the modern world. The species is native to the Mediterranean basin (Italy, southern France, Spain, Greece, Turkey, North Africa) and has been transported globally via human commerce since at least the early 1900s. The species is now established in temperate cities across North America (since the 1960s), South America, Australia, southern Africa, and East Asia — typically in urban environments where the species hides in basements, garages, attics, woodpiles, and other dark sheltered spaces. Adults are 7-9 mm body length with leg spans of 25-30 mm; coloration is light tan to dark brown with the characteristic dark violin-shaped marking on the dorsal carapace (giving genus members the nickname 'fiddleback spiders'). Like all Loxosceles, the species' eyes are arranged in three pairs (rather than the four pairs of most spiders) — a useful field-ID feature. The species' medical significance is the same as the more familiar brown recluse (L. reclusa) of the south-central US: venom contains sphingomyelinase D, an enzyme that destroys cell membranes and causes localized hemolysis. Bites typically cause a slowly-progressing necrotic ulcer at the bite site (loxoscelism) — initially painless, the bite progresses over 2-7 days into a 'red-white-blue' lesion (red erythema, central white ischemia, blue necrosis) that may eventually progress to a deep necrotic ulcer requiring weeks to months to heal. Severe systemic loxoscelism (with hemolysis, kidney failure, and DIC) is rare but documented. Antivenom is available in some Latin American countries but not in the US or Europe. The species is non-aggressive — bites occur primarily when the spider is squeezed against the body during dressing or sleeping. The species is one of the most-studied invasive arachnids in modern medical entomology.