brown recluse

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Closeup of a brown recluse spider, Loxosceles reclusa, blending into dry, brown grass and straw on the ground.

Brown recluse spider (Loxosceles reclusa).

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Also called:: violin spider

Related Topics:: Venom

On the Web:: National Center for Biotechnology Information - Brown Recluse Spider Toxicity (Oct. 25, 2026)

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brown recluse

Q: What is the deadliest spider?

The deadliest spider in the world is generally considered to be the Sydney funnel-web spider ( Atrax robustus ), a highly venomous species native to Australia. Its venom attacks the nervous system and can cause severe symptoms within minutes, including muscle spasms, breathing difficulty, and dangerously high blood pressure. Several human deaths from the bites of these aggressive spiders have been recorded in the Sydney area since the 1920s. Read Britannica’s list “9 of the World’s Deadliest Spiders.”

Q: Can a brown recluse bite kill you?

Deaths from the bite of a brown recluse spider are rare. Although the bite itself is painless at first, the cytotoxic venom can damage blood vessels and surrounding tissue, causing skin ulcers and necrotic lesions that may take months to heal. Serious complications, including infection and systemic reactions, occur only infrequently.

Q: Where are brown recluse spiders commonly found?

Brown recluse spiders are most commonly found in the western and southern United States. Outdoors, they often live in sheltered places such as caves and rodent burrows. Inside homes and buildings, they prefer dark, undisturbed areas including attics, storage spaces, closets, cardboard boxes, and wall or ceiling voids where they can hide during the day.

Q: What is distinctive about the brown recluse spider’s appearance?

The brown recluse is light tan or yellow in color and is noted for the dark violin-shaped design on its cephalothorax. It has a body length of about 7 mm (0.3 inch) and a leg span of about 2.5 cm (1 inch).

spider

Also known as: Loxosceles reclusa, violin spider

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Britannica Editors

Last updated

Oct. 25, 2026 •History

What is the deadliest spider?

Can a brown recluse bite kill you?

Where are brown recluse spiders commonly found?

What is distinctive about the brown recluse spider’s appearance?

brown recluse, (Loxosceles reclusa), species of venomous light tan or yellow spider most common in the western and southern United States. One of the most dangerous spiders in North America, the brown recluse is considered a medically significant spider and produces a cytotoxin that can cause necrotic lesions in humans and other animals.

The spider commonly makes its home in caves, rodent burrows, and other protected environments, and it often inhabits the undisturbed spaces of buildings, such as attics, storage areas, and wall or ceiling voids. Although females build flat, sheetlike webs, or “retreats,” brown recluse spiders are primarily hunting spiders and do not rely on webs to capture their prey. They typically hunt at night, roaming in search of insects and other arthropods.

(Read Britannica’s list “9 of the World’s Deadliest Spiders.”)

Sea otter (Enhydra lutris), also called great sea otter, rare, completely marine otter of the northern Pacific, usually found in kelp beds. Floats on back. Looks like sea otter laughing. saltwater otters

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Animal Group Names

Taxonomy

Kingdom: Animalia
Phylum: Arthropoda
Class: Arachnida
Order: Araneae
Family: Sicariidae
Genus: Loxosceles

See also list of spiders.

Physical description

The brown recluse has a body length of about 7 mm (0.25 inch) and a leg span of about 2.5 cm (1 inch). On the front half of its body (the cephalothorax), it has a dark violin-shaped design, the “neck” of which is formed by a conspicuous furrow on the midline of its back. This marking is not visible on young spiders. Unlike most other spiders, which have eight eyes, brown recluse spiders have six eyes arranged in two rows.

Bite

As their common name suggests, brown recluse spiders are shy and not aggressive, though they will bite defensively. Although the bite is painless and often goes unnoticed, the venom of the brown recluse soon destroys the walls of blood vessels near the site of the bite, sometimes causing a large skin ulcer. The venom contains a protein that targets phospholipid molecules—key components of cell membranes—and transforms these molecules into simpler lipids, causing cell death. The resultant wound, which may require several months to heal, is occasionally fatal due to infection, though deaths from brown recluse spider bites are rare.