The northern black widow is native but rare, documented in fewer than 10 counties, mostly east-central counties near Lake Michigan (Door County most).
UW-Madison Insect Diagnostic Lab (Division of Extension / Department of Entomology), P.J. Liesch: “In Wisconsin, these spiders are rare and have been documented in fewer than 10 counties.” Source
Venom: “Black widows and brown recluses are two types of venomous spiders in the United States.” (CDC / NIOSH)
Range: Rare; documented in fewer than 10 counties, mostly east-central counties near Lake Michigan (Door County most), also prairie areas in Crawford, Grant and Sauk counties (UW IDL 2018)
Official presence. 15 states where a state list or official source names it. Gray means no official record in our data, not that it is absent.
Native or listed
Nonnative or not established
No official record in our data
Observation records. Open-licence records on GBIF for the three US black widows (Latrodectus mactans, L. variolus and L. hesperus) in 44 states. Records are sightings people shared, not confirmation that a population lives there.
Chocolate brown and never has red on the belly; slightly smaller than a mature western black widow (about 3/8 in body length); egg sac looks like a cotton ball with indistinct margins. Caution: UC IPM says a black widow's hourglass can be almost imperceptible or, rarely, completely absent, so a lack of red alone does not rule out a black widow.
No red hourglass and not pure black; looks purplish-brown in bright light, and larger ones have a light T-shaped mark on the abdomen. Caution: a black widow's hourglass can rarely be almost or completely absent (UC IPM), so a lack of red alone does not rule out a black widow.
Usually a mottled mix of tan, brown and gray, with a lengthwise stripe and diagonal side stripes; colour varies from almost white to almost black, and very dark ones are flat black rather than shiny black. Mature females are smaller than mature female western black widows (about 3/8 in body length). The egg sac is covered in silk bumps, like a very large pollen grain; UC IPM calls the egg sac a much surer way to confirm a brown widow. Caution: brown widows also have a red hourglass on the underside (UF/IFAS), and a mature brown widow looks very similar to an immature western black widow (UC IPM).
Penn State Extension: the female common house spider is 5 to 6 mm long with a yellowish-brown carapace and a dirty-white to brown abdomen with gray chevrons; its legs are yellow with darker rings at the end of each segment.
Keep your distance and do not try to catch or handle it. Rattlesnake sightings: call DNR 1-888-WDNRINFO (1-888-936-7463), or use the DNR Rare Species Observation Form / DNR Wildlife Switchboard ([email protected], 608-267-0866). Threatening wolves or wolf depredation: USDA-Wildlife Services (north 1-800-228-1368, south 1-800-433-0663). Spongy moth outside quarantined counties: 1-800-642-MOTH (6684). Other invasive species: DNR Report invasive species page. Feral pig sightings: DNR reporting form or USDA Wildlife Services (north 800-228-1368, south 800-433-0663). Wisconsin Department of Natural Resources, Bureau of Endangered Resources
What official sources advise
Black bears: never feed or approach bears; in the woods stay calm, do not run, wave your arms, make noise and back away slowly. Wisconsin Department of Natural Resources
Black Widows: The Hermits of Door County. UW-Madison Insect Diagnostic Lab (Division of Extension / Department of Entomology), P.J. Liesch. May 22, 2018; checked November 3, 2026.Quoted passages (2)
“In Wisconsin, these spiders are rare and have been documented in fewer than 10 counties.”
“While we’re outside the native range of the dreaded, but horribly misunderstood brown recluse spider (Loxosceles reclusa), Wisconsin is actually home to a native black widow species—the northern black widow (Latrodectus variolus).”
“Black widows and brown recluses are two types of venomous spiders in the United States.”
Common Spiders In and Around Homes (PM 1722 / A2135 / FO-1033-B). University of Wisconsin-Extension with Iowa State University and University of Minnesota Extension (hosted by UW Insect Diagnostic Lab). Revised February 2012; checked November 3, 2026.Quoted passages (1)
“However, dangerous spiders such as the black widow and brown recluse, both very rare in the upper Midwest, require immediate attention and control.”
Black bear management. Wisconsin Department of Natural Resources. undated page; checked November 3, 2026.Quoted passages (1)
“If you encounter a black bear while in the woods, stay calm and do not run.”
