The brown recluse spider (Loxosceles reclusa) is common across the central and southern United States. This arachnid is often referred to as the “violin” or “fiddleback” spider because of a distinctive marking on its body. Its reputation stems from its venomous nature, which can occasionally lead to serious complications following a bite. Understanding this species is important for identification and safety.
Web Construction and Purpose
The brown recluse spider produces silk, but it is not a web-builder in the traditional sense. It is primarily a vagrant spider, meaning it actively hunts for its prey rather than relying on a sticky snare. Unlike orb-weavers, the brown recluse is a nocturnal hunter that leaves its shelter at night to find food.
The webbing it creates is an irregular, messy sheet that serves as a protective retreat or shelter. These disorderly silk strands typically line a hiding spot, providing a safe place for the spider to rest during the day. Female brown recluses also use this silk to construct small, off-white egg sacs.
Physical Identification Markers
Identifying a true brown recluse requires looking for a combination of features, as many harmless spiders are often misidentified. A defining characteristic is the dark, violin-shaped marking located on the cephalothorax (the fused head and chest section). The “neck” of this violin shape points toward the spider’s abdomen.
The most accurate identifier is the spider’s unique eye arrangement. While most spiders possess eight eyes, the brown recluse has only six eyes grouped into three pairs, or dyads. The spider’s legs and abdomen are a uniform color, ranging from tan to dark brown, and lack any stripes or distinct markings. The legs are covered in fine hairs, not the thick spines seen on many other common house spiders.
Typical Hiding Places and Behavior
The name “recluse” reflects this spider’s tendency to seek out secluded environments. They thrive in dark, dry, and undisturbed locations, whether indoors or outdoors. In natural settings, they favor areas like woodpiles, rock crevices, and under logs or debris.
When they move into human structures, they gravitate toward basements, attics, storage closets, and crawl spaces. Common indoor hiding spots include stored shoes, folded clothing piles, behind furniture, and within cardboard boxes. Bites almost always occur when a human accidentally compresses the spider against the skin, such as when putting on a shirt or shoe used as a daytime retreat. The spider does not seek to bite but does so defensively when it feels trapped.
Understanding the Brown Recluse Bite
A bite from a brown recluse is often painless initially, or it may feel like a minor sting or insect bite. The seriousness of the reaction is variable, but the majority of bites cause only minor, localized effects that heal without intervention. The venom contains an enzyme called sphingomyelinase D, which can cause tissue damage.
In a minority of cases, the bite can lead to a condition called loxoscelism, characterized by a necrotic lesion. Within a few days, the bite site may develop a blister, a surrounding area of redness, and central pallor, sometimes described as a bull’s-eye pattern. Systemic reactions, which can include fever, chills, nausea, and, very rarely, blood disorders, are uncommon but more frequently observed in children. Because many other skin conditions, including staph infections like MRSA, can mimic the appearance of a necrotic spider bite, diagnosis can be challenging. Immediate first aid should involve cleaning the wound and applying a cold compress, and medical attention is recommended if a painful, worsening lesion or systemic symptoms begin to develop.