Black Widows

Black widow spiders and their bites 

Black widow spiders are among the most venomous spiders in North America. While both males and females have venom, only mature females pose a real risk to people. Males and immature females are much smaller, with weaker jaws that usually cannot puncture human skin. 

Although the mature female’s venom is strong, bites are rarely fatal. Most cause temporary but painful symptoms that can be managed with medical care. Knowing how to recognize, avoid and respond to black widow spiders can help keep you and your family safe - especially around woodpiles, sheds, patios or outdoor furniture where these spiders like to hide. 

How to identify a black widow spider 

Black widow spiders (Latrodectus mactans) are easy to recognize once you know what to look for.  

Here’s how to tell the difference between mature females, males and juveniles: 

Mature females (dangerous to people): 

• Shiny black body with a large, round abdomen 
• About 3/8 inch long, with legs extending up to 1 inch 
• A bright red or orange-red hourglass marking on the underside of the abdomen 
• Larger and bulkier than males, with a lifespan of up to 1–3 years 

Immature females (juveniles): 

• Smaller, often brown or gray with lighter striping or mottled patterns 
• Hourglass marking may be yellow, orange or not fully formed 
• Less dangerous because their venom glands are not fully developed 

Males: 

• Much smaller and slimmer than females, usually half the size 
• Brown or gray rather than glossy black 
• May have faint red, orange or yellow markings but not the bold hourglass 
• Short lifespan of only a few months 
• Rarely bite and usually cannot puncture human skin 

Common hiding places 

Black widows weave irregular, strong white webs in sheltered locations where insects are plentiful, such as: 

• Under outdoor furniture or barbecue grills 
• Near pool pumps, storage areas, sheds or garages 
• In corners of porches and patios 
• Around woodpiles, lumber or rocks 

These spiders stay close to their webs and wait for prey, rather than hunting. 

Symptoms of a black widow spider bite 

Bites usually happen when a spider is disturbed, such as when moving firewood or cleaning storage areas. Many people don’t notice the bite right away. 

Early signs may include: 

• A pinprick sensation at the bite site 
• Little or no swelling initially 
• A red circular mark that may appear several hours later 

Progressive symptoms can include: 

• Aching or cramping pain at the bite site 
• Muscle pain that spreads to the abdomen, lower back, thighs and limbs 
• Headache, nausea, sweating or restlessness in some cases 

Most symptoms last up to 36 hours. Mild lingering effects, such as soreness or fatigue, may continue for several weeks. 

What to do if you are bitten 

If you suspect a black widow bite: 

1. Call the poison center immediately at 800-222-1222. They will advise whether home care is safe or if emergency treatment is needed. 
2. Seek medical care right away if the person bitten is very young, elderly or has health conditions that affect their immune system. 
3. Treatment in the hospital may include: 

• Pain medications
• Muscle relaxants
• Anti-venom in severe cases 

Do not wait for symptoms to worsen. Early care makes a big difference. 

How to prevent black widow bites 

Black widows are most active at night and usually hide during the day in sheltered spots. To reduce your risk: 

• Inspect your yard regularly: Look for irregular white webs in and around outdoor areas. 
• Remove webs and egg sacs: At night, use a flashlight to locate webs, spray the spider directly with insecticide and destroy egg sacs (small, round white balls filled with spiderlings). 
• Wear protective gloves: Always wear gloves when handling firewood, rocks or debris. Check inside gloves before putting them on. 
• Reduce clutter: Keep sheds, patios and storage areas clean and free of piles where spiders may hide. 

Using insecticides safely 

Many pesticides are labeled for spider control. Some are available for homeowners, while others must be applied by licensed pest control professionals. 

• Apply insecticide directly to the spider or her web. 
• Follow the product label closely for safety. 
• If you’re unsure, consider hiring a professional pest control company. 

When to call for help 

If you need medical advice about a black widow spider bite: 

• Call the Poison Center at 800-222-1222. 
• In Arizona, contact the Banner Poison and Drug Information Center at 602-253-3334. 

Quick action can reduce symptoms and prevent complications.