Black Widow Spiders in Missouri

Black widow spiders are present throughout Missouri, though they are less commonly encountered in homes than brown recluses. Understanding where they live, how to identify them, and what the genuine bite risk is can help Missouri homeowners respond appropriately when they encounter one — or take steps to reduce the likelihood of an encounter.

Identifying Black Widow Spiders in Missouri

Missouri is home primarily to the Northern black widow (Latrodectus variolus) and the Southern black widow (Latrodectus mactans). Both are identifiable by:

• Female: Shiny black, round abdomen with a red hourglass marking on the underside. The hourglass may be broken into two separate red spots in Northern black widows. Body length approximately 8–13mm, with long dark legs giving a total size up to 38mm leg-to-leg.
• Male: Smaller than females, lighter colored with whitish or yellow markings, and not considered medically significant — only females have the venom potency that makes this spider notable.
• Web: Black widows build irregular, messy webs close to the ground — not the symmetrical orb webs most people picture. The web has a characteristic tangled structure and is extremely strong and sticky.

Where Black Widows Are Found in Missouri

Black widows strongly prefer outdoor or semi-outdoor environments and are far less commonly found living inside finished living spaces than brown recluses. In and around Missouri homes, they are most often found in:

• Undisturbed outdoor areas — woodpiles, rock piles, dense vegetation, debris piles
• Outbuildings — sheds, barns, detached garages, crawlspace vents
• Attached garages, especially corners at floor level and behind stored items
• Crawlspaces, particularly around foundation vents
• Outdoor furniture that has been unused for a period
• Meter boxes and other outdoor utility enclosures

Black Widow Bite Risk

Black widows are not aggressive and will not pursue a person. Bites occur when the spider is accidentally disturbed or pressed against skin. Common bite scenarios include reaching into a woodpile, putting on a glove or shoe that had a spider inside, or moving outdoor furniture that has been undisturbed.

Black widow venom is a neurotoxin — it affects the nervous system rather than causing tissue death like brown recluse venom. Symptoms of a significant bite can include muscle pain and cramping (often in the abdomen and back), sweating, elevated heart rate, and nausea. Fatalities from black widow bites are extremely rare with modern medical care, but bites can cause serious symptoms that warrant prompt medical attention — especially in children, elderly individuals, or those with underlying health conditions.

Any suspected black widow bite should be evaluated by a physician promptly. Capture the spider if possible for identification.

Prevention Around Missouri Properties

• Store firewood away from the house on an elevated rack and inspect it before bringing wood inside
• Wear work gloves when handling firewood, moving rocks, or working in areas where spiders may be present
• Shake out shoes, gloves, and clothing that have been stored in garages or sheds
• Reduce debris, rock piles, and dense vegetation adjacent to the foundation
• Inspect outdoor furniture before use after a period of non-use
• Keep garages and sheds organized and reduce clutter at floor level

Professional Treatment

Because black widows live primarily in outdoor and semi-outdoor environments, exterior perimeter treatments and targeted spot treatments in high-risk areas (crawlspaces, garage perimeters, outbuildings) are the most effective approach. If black widows are being found frequently around a property, a professional inspection can identify the harborage locations and recommend appropriate treatment.