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Overview

Brief Summary

The shiny black body and legs of the Northern Black Widow (Latrodectus variolus) are striking. The globose abdomen is typically decorated on its underside with two usually distinct red marks and has a row of red spots extending down the upper side of the abdomen (the slightly smaller Southern Black Widow, L. mactans, which has an overlapping distribution but is more common in the southern part of its range, often lacks these dorsal spots and the red markings on the underside of the abdomen are usually joined together in an hourglass shape). The much smaller male has abdominal markings that are more red-orange and a continuous or broken red-orange stripe bordered by white down the dorsal midline of the abdomen, as well as several pairs of diagonal white stripes along the sides of the abdomen. Young females often show a pattern similar to that of males. Female length is around 9 to 11 mm, but males are only 5.5 to 6 mm long.

The Northern Black Widow makes an irregular web of very strong and coarse silk, usually near the ground around tree stumps, in woodpiles, under stones and loose bark, around water faucets, in holes in the ground, and in garages, barns, storage buildings, and outhouses. When possible, it will retreat in the presence of a human interloper. Often the egg sac can be seen within the irregular web, guarded by the female. The somewhat pear-shaped egg sac is pale gray to yellow or tan, around 13 to 14 mm in length and 10 to 12 mm in diameter, most often spreading at the top.

Although the Northern Black Widow is widely distributed in the eastern United States (east of Kansas, Oklahoma, and Texas), it is more common in the northern part of its range. Most people who are bitten by these spiders have accidentally trapped the spider against their body or touched the web. Anyone bitten by a black widow should seek professional medical attention immediately. Vetter and Isbister (2008) provide a recent review of medical aspects of spider bites.

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  • Howell, W.M. and R.L. Jenkins. 2004. Spiders of the Eastern United States: a Photographic Guide. Pearson Education, Boston.
  • Kaston, B.J. 1978. How to Know the Spiders, 3rd edition. Wm. C. Brown Company, Dubuque, Iowa.
  • Vetter, R.S. and G.K. Isbister. 2008. Medical aspects of spider bites. Annual Review of Entomology 53: 409-29.
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Distribution

National Distribution

Canada

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

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Conservation

Conservation Status

NatureServe Conservation Status

Rounded Global Status Rank: GNR - Not Yet Ranked

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National NatureServe Conservation Status

Canada

Rounded National Status Rank: NNR - Unranked

United States

Rounded National Status Rank: NNR - Unranked

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Wikipedia

Latrodectus variolus

Latrodectus variolus, the Northern black widow spider or Northern widow, is a venomous spider species of the Latrodectus genus in the Theridiidae family. The population is closely related to the Southern Black Widow, Latrodectus mactans, and the Western Black Widow, Latrodectus hesperus, of the genus.

It is a common find in Middle Atlantic States (New Jersey, Delaware, Maryland). During the April–May mating season, it can travel northbound along the coast to as far as Massachusetts. It also occurs in Connecticut in late summer. It is also found, albeit rarely, in southern Ontario, Canada.

The bite is unpleasant, but not medically significant[1] unless it triggers an allergic reaction in the central nervous system. Seeing a doctor is usually suggested within a couple of hours after the bite or the symptoms appear. The LD-50 has been measured in mice as 1.80 milligrams (0.0278 gr) (with a confidence interval of 1.20-2.70), and each spider contains about 0.254 milligrams (0.00392 gr) of venom.[2]

References[edit]

  1. ^ Northern Black Widow Spider (Latrodectus variolus). 
  2. ^ McCrone, J.D. (December 1, 1964). "Comparative lethality of several Latrodectus venoms". Toxicon 2 (3): 201–203. doi:10.1016/0041-0101(64)90023-6. 
  • Platnick, N. I. 2008. Theridiidae The World Spider Catalog, version 9.0. American Museum of Natural History.
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