The presence of spiders in and around homes can cause concern, particularly regarding species that may pose a risk to human health. In Wisconsin, the perception of dangerous spiders often outweighs the actual threat. Understanding which spiders are truly of concern and how to respond to their bites is important for peace of mind and safety. This article distinguishes between common, harmless spiders and those few species that require more caution.
Identifying Spiders of Concern in Wisconsin
Wisconsin is home to many spider species, but only a few are considered medically significant. The Northern Black Widow (Latrodectus variolus) is a native spider, though it is rarely encountered by most residents. Adult female Northern Black Widows are typically glossy black or dark brown, with a distinctive red hourglass marking on their underside. Some also have red spots or bars on their dorsal side or legs. They prefer secluded habitats like under rocks, in woodpiles, block walls, garages, or sheds.
The venom of the Northern Black Widow is neurotoxic, meaning it affects the nervous system. A bite may initially feel like a pinprick, or it might go unnoticed. Within an hour, dull muscle pain can spread from the bite site, often localizing in the abdomen, chest, or back, with severe cramping. Other symptoms include nausea, vomiting, sweating, headache, and increased blood pressure. While symptoms can be intense, severe reactions usually improve within two to three days, and fatalities are uncommon.
The Brown Recluse (Loxosceles reclusa) is often mentioned as dangerous, but it is not native to Wisconsin and its presence is extremely rare. Confirmed sightings are usually “hitchhiker” spiders accidentally transported into the state. This small, tan or brown spider is identified by a violin-shaped marking on its carapace. Brown recluse bites are uncommon; these spiders are not aggressive and typically bite only when trapped against skin. While their venom can cause a necrotic lesion in rare cases, many suspected bites are misdiagnosed.
Responding to Bites and Preventing Encounters
If a spider bite occurs, first aid measures can help manage symptoms. The bite area should be cleaned with mild soap and water. Applying a cool compress or ice pack for 15 minutes each hour reduces pain and swelling; elevating the affected area is also recommended. Over-the-counter pain relievers help with discomfort, and an antihistamine may alleviate itching.
Seek medical attention if concerned about a Northern Black Widow bite or if symptoms are severe. These include intense pain, spreading redness or streaks, stomach cramping, or difficulty breathing or swallowing. Consult a healthcare professional if symptoms worsen after 24 to 48 hours. While antivenom exists for black widow bites, it is used with caution due to potential allergic reactions.
Preventing spider encounters involves practical steps around the home. Reducing clutter in basements, attics, and garages removes spider hiding spots. Sealing cracks and gaps in foundations, windows, and doors prevents spiders from entering living spaces. Outdoors, maintaining a tidy yard by trimming bushes, clearing debris, and keeping woodpiles away from the house deters spiders. Shaking out clothing and shoes before wearing them, and wearing gloves when working in areas like woodpiles or crawlspaces, minimizes accidental bites.