Invertebrates
Brown Recluse Spider
Loxosceles reclusa · also called brown recluse spider, violin spider, fiddleback spider
The brown recluse spider lives up to its name. It hides in quiet, dry, undisturbed corners, avoids people entirely, and bites only when trapped — usually inside a shoe or a shirt someone is putting on. Most of its bites are minor. A minority, in a small number of cases, slowly destroy the surrounding tissue.
Overview
Brown recluse spiders live in the south-central and southern United States, sheltering by day in boxes, clothing, shoes, woodpiles, and undisturbed clutter. They are small — 6–12 mm — plain brown, with a darker violin-shaped mark on the back and, unusually, six eyes instead of eight. They hunt small insects at night, roaming rather than building a snare web.
The bite
Most bites cause only mild redness and itching. A minority develop a slow-spreading, tissue-destroying wound from the venom’s enzyme, which can take weeks to heal. Severe reactions are rare, and there is no widely available antivenom.
Over-blamed
Because the spider is shy and rarely seen even where it lives, and it is essentially absent from most of the US, “recluse bite” is a common misdiagnosis for skin ulcers actually caused by infections or other conditions.
Status
The brown recluse is Not Evaluated, common within its native range and not threatened, with isolated indoor populations elsewhere from transported goods.
Brown Recluse Spider: common questions
How dangerous is a brown recluse bite?
Most bites are far less dramatic than their reputation suggests. Many recluse bites cause no more than a mild sting, some redness, and localised itching or swelling that resolves on its own within days. In a minority of cases, the venom's tissue-destroying enzyme causes a more serious reaction — the bite site can develop a spreading area of redness, blistering, and eventually a deep, slow-healing ulcer as the surrounding tissue dies, a process called necrotic arachnidism, which can take weeks to months to heal and occasionally needs medical or surgical treatment. Severe systemic reactions affecting the whole body are rare but have occurred, more often in children. There is no widely available antivenom, and treatment is mainly supportive, so any suspected bite that worsens should be seen by a doctor.
How can you identify a brown recluse spider?
Three features together are the most reliable check, since colour and general shape alone are not distinctive enough. First, look for a darker violin- or fiddle-shaped marking on the top of the cephalothorax, with the "neck" of the violin pointing backward toward the abdomen, though this mark can be faint or absent in some individuals. Second, count the eyes if possible — a brown recluse has six eyes arranged in three separated pairs, while almost all other common house spiders have eight. Third, the legs and body are uniformly coloured with no obvious stripes, bands, or spots, and the legs have fine, short hairs rather than obvious spines. Because several harmless spiders resemble it in general shape and colour, positive identification often requires close inspection or an expert.
Why do so many skin injuries get blamed on brown recluse spiders outside their actual range?
The brown recluse has a defined native range in the south-central United States, and it is genuinely rare or absent across huge parts of the country, yet doctors in areas with no established populations regularly diagnose "brown recluse bites" based on a skin lesion alone. Research has repeatedly shown that a wide range of other causes, including bacterial infections such as MRSA, other insect and spider bites, and various skin conditions, produce sores that look similar to a necrotic spider bite, and that a confirmed brown recluse bite normally requires that the spider itself was seen, caught, and identified. Because the spider is shy, nocturnal, and rarely seen even where it lives, "recluse bite" has become a default explanation for unexplained skin ulcers well beyond where the species actually occurs.
How can you avoid being bitten by a brown recluse?
Since bites almost always happen when the spider is accidentally trapped against skin, the standard precautions in areas where it lives are to shake out and inspect shoes, gloves, and clothing that has been stored or left on the floor, especially in garages, sheds, attics, and basements, before putting them on; move stored boxes and firewood carefully and wear gloves when handling long-undisturbed clutter; and reduce clutter and seal cracks and gaps that provide hiding spots indoors. Because the spider is passive and will not attack unprovoked, most bites are entirely preventable simply by not startling or pressing against one hidden in fabric or a dark corner.