The black widow spider is widely known for its potent venom. The female black widow is especially well-known for its neurotoxic venom, which can affect the nervous system. Understanding this spider’s characteristics and habits can help clarify its presence in various environments.
Black Widows in Wisconsin
Wisconsin is home to a native black widow species, the Northern Black Widow (Latrodectus variolus). While present, these spiders are generally rare, and most Wisconsinites may go their entire lives without encountering one in nature. Documented sightings have occurred in fewer than 10 counties, primarily in the east-central part of the state. Door County has historically reported the most confirmed sightings, suggesting a localized area of higher prevalence.
The presence of Northern Black Widows further north in Wisconsin is limited, likely due to colder winter conditions. However, localized microclimates, such as south-facing slopes in prairie areas of counties like Sauk, Crawford, and Grant, can favor their survival. A notable increase in reported sightings occurred in 2017, possibly linked to milder preceding winters.
Identifying Black Widows
Identifying a black widow spider involves observing distinct visual characteristics, particularly for the female, which is medically significant. Adult female Northern Black Widows typically have shiny black bodies, measuring around 13 millimeters. A key identification mark is the red or orange hourglass shape on the underside of their abdomen.
The Northern Black Widow’s hourglass marking is often distinct but broken, unlike the complete hourglass seen on other black widow species. These spiders may also display a row of red spots along the top (dorsal) side of their abdomen, and sometimes have diagonal whitish bands, especially when younger. Male black widows are considerably smaller than females, usually about half their size, and may feature orange and brown markings at their leg joints or red and white stripes on their abdomen.
Black widow spiders construct irregular, messy, and tangled webs, known for their strength and stickiness. These webs are typically found near ground level, often under protected ledges or in secluded corners. The female spider frequently hangs upside down in her web, making her distinctive hourglass marking visible.
Where Black Widows Live and Behave
Black widow spiders prefer dark, secluded, and undisturbed areas. Outdoors, they are commonly found in woodpiles, hollow logs, stumps, and under rocks or debris. They also establish themselves in human-made structures like sheds, garages, and basements, often in cluttered spaces or hidden crevices.
While black widows primarily live outdoors, they can occasionally be inadvertently brought into homes on items like firewood or stored goods. These spiders are reclusive and nocturnal, meaning they are most active at night. They are not aggressive and typically bite only when threatened, such as when their web is disturbed or if pressed against human skin.
Safety and Prevention
If a black widow spider bite occurs, the initial sensation might feel like a slight pinprick or go unnoticed. Within 15 minutes to an hour, a dull muscle pain can spread from the bite site to other body parts, often settling in the abdomen or back. Other symptoms include severe muscle cramps, nausea, vomiting, sweating, headache, and fever, potentially lasting for several days.
Immediate first aid for a black widow bite involves cleaning the affected area with soap and water. Applying an ice pack, wrapped in a cloth, to the bite site can help reduce pain and swelling and potentially slow venom spread. Keep the affected area as still as possible. Seek medical attention promptly, especially if symptoms are severe or if the bite victim is a child or elderly individual. Fatalities from black widow bites are rare.
Preventative measures can reduce the likelihood of encountering black widows around your home. Sealing cracks and gaps in foundations, windows, and doors prevents spiders from entering. Reducing clutter in basements, garages, and other storage areas eliminates potential hiding spots. Storing firewood away from the house and off the ground, and regularly trimming vegetation, can also deter these spiders.