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Clinical manifestations and diagnosis of widow spider bites

David L Swanson, MD
Richard S Vetter, MS
Julian White, AM, MB, BS, MD, FACTM
Section Editors
Stephen J Traub, MD
Daniel F Danzl, MD
Deputy Editor
James F Wiley, II, MD, MPH


This topic will review the biology of widow spiders (genus Latrodectus) and the clinical manifestations, diagnosis, and differential diagnosis, of their bites. Management of widow spider bites, an overview of spider bites, and the management of bites of other spiders are discussed separately. (See "Approach to the patient with a suspected spider bite: An overview" and "Bites of recluse spiders".)


Both widow spiders and false widow spiders are of medical importance, although the bites of the former are generally of greater concern.

Widow spiders (Genus Latrodectus) — Widow spiders belong to the family Theridiidae, genus Latrodectus. Latrodectism is the term for the medical manifestations of bites by widow spiders [1,2]. (See "Approach to the patient with a suspected spider bite: An overview".)

There are approximately 30 species of widow spiders found worldwide [3]. Not all have been implicated in human bites, although this may be partly due to the remote distribution of the spiders away from human populations. Female widow spiders are responsible for most significant bites. Males have less venom, smaller fangs, and weaker biting muscles.

Identification — Most adult widow spiders are shiny black with red markings on the body, although this is not universal. American widow spiders range from 5 to 15 mm (0.25 to 0.5 inch) in total body length with an abdominal diameter of about 10 mm (0.5 inch). The most common species of medical importance are the following:

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Literature review current through: Nov 2017. | This topic last updated: Nov 28, 2017.
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