Danger Level: 5/5

Black Widow Spider

Latrodectus hesperus

Updated May 2026 · Boise, ID

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Quick Facts

SizeFemale: 8-15mm body, Male: 3-4mm

ColorShiny black with red hourglass

Lifespan1-3 years

Active SeasonsSpring, Summer, Fall

Common LocationsGarages, Sheds, Woodpiles

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Identification

How to Identify Black Widow Spider

Quick Answer

Females are shiny jet-black with a red hourglass on the underside of a globular abdomen. That hourglass is the giveaway.

Females are shiny jet-black with a red hourglass on the underside of a globular abdomen. That hourglass is the giveaway. Bodies run 8-15mm with leg spans up to 50mm; males are much smaller (3-4mm), brown, and not dangerous to people. The webs are irregular, tangled, and noticeably tougher than a typical cobweb.

Black Widow Spider - showing key features for identification

Behavior

Black Widow Spider Behavior & Habits

Understanding how black widow spider behave helps prevent infestations

Signs You Have Black Widow Spider

What homeowners spot first

Irregular, tangled webs in dark corners
Webs in garage corners, under decks, in meter boxes
Round, cream-colored egg sacs in webs
Actual spider sightings (usually at night)
Webs that feel exceptionally strong

Black widows are shy and almost never aggressive. They bite when trapped against skin or when a hand sweeps blindly into a web, not on purpose. They're nocturnal, hide in dark undisturbed spots during the day, and build their irregular webs low to the ground to catch ground-dwelling insects. Females sometimes eat males after mating, which is where the name comes from.

Dangers

Black Widow Spider Risks & Dangers

What black widow spider can do to your health and property

Health Risks

Black widow venom is neurotoxic and roughly 15 times stronger than rattlesnake venom drop-for-drop. Bites cause severe pain, muscle cramps, abdominal pain, and elevated blood pressure. Healthy adults rarely die from a bite, but every confirmed bite warrants a trip to the ER or urgent care. Kids, older adults, and anyone with heart or other health conditions are at higher risk.

Property Damage

Black widows don't damage property, but a single web in a water meter box, garage corner, or shed creates ongoing bite risk every time you reach in.

Warning Signs

Signs of Black Widow Spider Infestation

Look for these indicators in your home

Irregular, tangled webs in dark corners

Webs in garage corners, under decks, in meter boxes

Round, cream-colored egg sacs in webs

Actual spider sightings (usually at night)

Webs that feel exceptionally strong

Black Widow Spider in Boise & the Treasure Valley

Black widows are a steady call across the Treasure Valley, with our heaviest volume running May through early October. We pull them most often out of water meter boxes near the curb, irrigation valve boxes, the back corners of garages behind stored boxes, and woodpiles stacked against the house. Older Boise neighborhoods like the North End, East End, Vista, and the Bench see them in original block foundations and detached garages, but plenty of newer builds in Meridian and Eagle have them too wherever a garage stays cluttered or a shed sits unused for a season. Idaho's dry summers and the warm cinder-block voids that hold heat overnight suit them just fine.

Our Solution

How We Eliminate Black Widow Spider

Professional treatment for complete elimination

Black widows hide in garages, sheds, water meter boxes, woodpiles, and any quiet outdoor corner, so that's where we hit them. Our $49 initial service covers a hands-on sweep of those harborage spots plus a long-residual perimeter treatment that stays effective for months under cover. Quarterly visits keep populations down by also cutting off the prey insects they feed on, and our free re-service guarantee covers callbacks if you spot one between visits.

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Prevention

How to Prevent Black Widow Spider

Steps you can take to reduce the risk of infestation

Wear gloves when moving stored items or firewood

Shake out shoes, gloves, and clothing left outside

Reduce clutter in garages and sheds

Keep garage doors closed

Clear vegetation and debris from foundation

Use outdoor lighting that doesn't attract insects

FAQ

Black Widow Spider Questions Answered

Common questions about identification, prevention, and treatment

How common are black widows in Boise?

Common enough that we run black widow service calls every week from late spring through October. The heaviest concentrations sit in older Boise neighborhoods like the North End, East End, Vista, and the Bench, plus any home in Meridian or Eagle with a cluttered garage, woodpile, or untouched shed. Water meter boxes near the curb are the single most common spot we find them.

What should I do if I'm bitten by a black widow?

Get to the ER or an urgent care right away. Clean the bite with soap and water, apply a cold pack, and if you can do it safely, capture the spider in a sealed container for identification. Most bites are treatable, but the pain and muscle reactions can be severe enough to need medical care, and kids and older adults need to be seen immediately.

How do I prevent black widow bites?

Wear gloves any time you reach into a water meter box, move firewood, or pull stored items off a garage shelf. Shake out shoes, gloves, and clothing left in the garage or outside. Quarterly pest control cuts populations dramatically by killing both the spiders and the prey insects that draw them in. Our $49 initial service gets you started, and the free re-service guarantee covers callbacks if you see one between visits. Call (208) 297-7947 to book.