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February 3, 2012
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Black Widow Spider Bite

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Black Widow Spider Bite Overview

Of the 30,000 types of spiders, the black widow is probably the one best known and feared. Although spiders are often blamed for all kinds of symptoms, from local itching to diffuse rashes, the fact is that spiders rarely bite humans, and in fact, most spider bites do not even break the skin.

The bites of very large spiders such as tarantulas can be painful. Otherwise, in the temperate regions, the only spiders to be feared are the black widow and the brown recluse.

  • The black widow is a medium-sized spider whose body is about a half-inch long. The name is derived from the mistaken belief that the female invariably kills the male after mating. Although the spider is mostly found in the southern United States, it may be seen throughout the US. Five species are common to the US, with two of them being the most common:

    • The southern black widow has the shiny, black, globular abdomen with the distinctive red hourglass on the underside.

    • The northern black widow has a row of red spots down the middle of the upper surface of its abdomen and two crosswise bars on the undersurface. The markings can also be yellow or white, and the spider itself may be brown or have red legs.

  • Black widow spiders are nocturnal and, thus, are active at night. They prefer dark corners or crevices. They are said to avoid human dwellings, but you can find them in such areas as outhouses and garages. Only the female black widow bites humans, and she bites only when disturbed, especially while protecting her eggs.

Picture of the underside of a black widow spider and an egg sack

Picture of the underside of a black widow spider and an egg sack

 

Picture of a top view of a black widow spider

Picture of a top view of a black widow spider

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Black Widow Spider Bite

Topic Overview

What is a black widow spider?

Black widow spiders (Latrodectus mactans and Latrodectus hesperus) are found throughout the United States, Mexico, and southern Canada. 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 shape on their underside that usually looks like an hourglass but may be another shape. Female black widows are usually about 1.5 in. (3.8 cm) long, but may be smaller.

Black widow spiders are frequently found in low-lying webs in garages, barbecue grills, around swimming pools, and in wood piles. Most bites occur in rural and suburban areas and occur between the months of April and October. These spiders tend to bite defensively when their webs are disturbed. Bites to babies and children may be more serious than bites to adults.

What are the signs and s...

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Read What Your Physician is Reading on Medscape

Spider Envenomation, Widow »

Widow spiders belong to the genus Latrodectus and include the black widow spider (Latrodectus mactans mactans) in the United States.

Read More on Medscape Reference »

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