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Black Widow Spider

Black widow spiders (Latrodectus mactans) are found throughout the Western Hemisphere. A female black widow is much more likely to deliver more venom than a male spider.

Female black widows are long-legged, shiny, coal-black spiders with an orange, red, or yellow hourglass shape on the underside. The female black widow is usually about 1.5 in. (3.8 cm) long, but may be smaller.

Black widow spiders tend to bite defensively when their webs are disturbed. Black widow spiders are frequently found in low-lying webs in garages, barbecue grills, around swimming pools, and in wood piles. Bites to babies and children may be more serious than bites to adults. Signs and symptoms of a black widow bite include:

  • Minimal pain at first, followed by sharp pain and swelling and redness at the site of the bite.
  • One or two small fang marks like tiny red spots.

In some cases, severe symptoms appear within 30 to 60 minutes. These include:

  • Muscle cramps and spasms that start near the bite and then spread and increase in severity for 6 to 12 hours.
  • Chills, fever, nausea, or vomiting.
  • Sweating.
  • Severe abdominal, chest, or back pain.
  • Headache.
  • Stupor, restlessness, or shock.
  • Severe high blood pressure.

A doctor should be contacted immediately when a person is bitten by a black widow spider.

Last Revised: October 14, 2011

Author: Healthwise Staff

Medical Review: William H. Blahd, Jr., MD, FACEP - Emergency Medicine & H. Michael O'Connor, MD - Emergency Medicine

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