Deadly Spiders in Wisconsin: Black Widows, Brown Recluses & Bites

Deadly Spiders in Wisconsin

Wisconsin is home to a diverse array of spider species, though most are not considered medically significant to humans. However, there are two types of spiders found in the state that are notorious for their potentially dangerous bites the northern black widow and the brown recluse.

Northern Black Widow Spiders

The northern black widow (Latrodectus variolus) is found throughout Wisconsin as well as other parts of the United States and Canada. It gets its name from the tendency of the female to occasionally eat the male after mating. Northern black widows produce a neurotoxic venom that can cause severe pain, muscle cramping, and other medical issues in humans, though deaths are very rare.

Identification

Female black widows are shiny black in color with a prominent red hourglass marking on the underside of their large spherical abdomens. They have long slender legs and measure about 1.5 inches in body length. Male widows are smaller, lighter in color, and lack the signature hourglass.

Bites & Symptoms

Bites most often occur when the spider is disturbed or unintentionally contacted by a human. Initial bite symptoms include pain, swelling, and pinprick wound marks at the bite site. More severe systemic effects can follow within a few hours, including painful muscle spasms, abdomina pain, nausea, and difficulty breathing.

Treatment

See a doctor immediately if bitten by a northern black widow. Antivenom can be administered to alleviate symptoms. Pain medications, muscle relaxers, IV fluids, and other supportive medical care may be provided.

Outlook

With proper medical treatment, most black widow bites have good outcomes. But in rare cases seizures, high blood pressure, and respiratory distress can occur and may become life threatening. Children, elderly, and those with existing medical issues are most at risk.

Brown Recluse Spiders

The brown recluse spider (Loxosceles reclusa) is also found in Wisconsin, primarily restricted to the southwestern part of the state. This spider is native to midwestern and southeastern states. Though not aggressive, it may bite if touched or pressed up against the skin.

Identification

As the name suggests, this spider has a uniformly brown coloration. The legs lack distinct banding and the oval body is about 0.5 inches long. A key identifier is the violin-shaped marking on the top surface of the cephalothorax (fused head and thorax).

Bites & Symptoms

Most brown recluse bites are minor with mild stinging. In some cases, more severe symptoms occur like pain, itching, nausea, fever and vomiting. Rarely, tissue damage develops due to the cytotoxic venom components leading to a necrotic sore.

Treatment

See a doctor if you suspect a brown recluse bite. The wound will be examined and monitored, with antibiotics sometimes prescribed to prevent infection. Medications can alleviate pain and other symptoms. Surgery may be needed to remove dead tissue if a necrotic lesion forms.

Outlook

Though alarming in appearance, most brown recluse bites heal well with proper care. Serious complications are very uncommon but can include seizures, kidney failure, blood disorders, and loss of limbs in extremely rare cases.

Other Wisconsin Spiders

The vast majority of Wisconsin's hundreds of spider species pose no safety risk to people. Here are some of the other spiders that call the state home:

Grass Spiders

Grass spiders (Agelenopsis species) are frequently encountered in backyards, gardens, grassy areas, and fields across Wisconsin. They build funnel-shaped webs to trap insect prey. Their bites occasionally cause mild skin irritation but are not medically significant.

Jumping Spiders

More than 300 species of jumping spiders (Salticidae family) inhabit Wisconsin nature reserves and backyards. As their name suggests, they actively hunt by jumping on their prey rather than building webs. Jumping spiders rarely bite humans.

Orb Weavers

Orb weaver spiders spinning large, intricate circular webs are a common sight in Wisconsin gardens and woodlands. Examples include garden spiders (Araneus diadematus), banded garden spiders (Argiope trifasciata), and black and yellow garden spiders (Argiope aurantia). They help control mosquitos and other pests and do not pose a risk to people.

Cellar Spiders

Long-legged cellar spiders (Pholcus phalangioides) with tiny bodies frequently build messy-looking webs in basements, cellars, and other dark spaces in Wisconsin homes. They have small fangs incapable of penetrating human skin.

Fishing Spiders

Wisconsins lakes, rivers, and streams are home to giant fishing spiders (Dolomedes species). They dive underwater and use their fangs to catch small fish and aquatic insects. Some can reach 3 inches in legspan! Their bites are generally harmless to people.

Crab Spiders

Crab spiders with a laterigrade leg posture (to the side) stalk prey rather than building webs. Some common ones in Wisconsin include whitebanded crab spiders (Misumenoides formosipes) and elegant crab spiders (Xysticus elegans). They rarely come into contact with people but may bite if handled roughly.

Preventing Spider Bites

Use these tips to help avoid bites from venomous spiders in Wisconsin homes and outdoor spaces:

• Seal cracks and gaps around foundations and windows to discourage spiders from entering.
• Reduce clutter like piles of wood, rocks, and debris where spiders may hide.
• Inspect or shake out clothing, shoes, towels, and bedding before use if they've been on the floor.
• Use gloves and protective clothing when cleaning unused outdoor sheds and garages.
• Install yellow bug lights at home entries that are less attractive to insects (and the spiders that feed on them).

See a doctor right away if bitten by a spider you can't identify or if concerning symptoms develop. With prompt medical care the outlook for recovery is excellent in most cases.

Disclaimer: This article is for informational purposes only and does not constitute medical advice. Always consult with a healthcare professional before starting any new treatment regimen.