Triangulate Cobweb Spiders in Idaho: Identification, Safety, and How to Get Rid of Them

Triangulate cobweb spiders are one of the most common indoor spiders found across Idaho, including homes throughout Boise, Meridian, Nampa, Caldwell, and surrounding areas. They belong to the genus Steatoda, a group sometimes referred to as “false widows” because their rounded bodies can resemble widow spiders at a quick glance. Fortunately, triangulate cobweb spiders are generally not a high-risk spider for homeowners, and their venom is far less potent than true widow spiders.

These spiders can be beneficial because they feed on insects (and sometimes other spiders), but they become a nuisance when webs build up throughout basements, garages, storage areas, and quiet corners of the home. If you want help reducing spider activity, you can learn more about local options on our spider control page.

How to Identify Triangulate Cobweb Spiders

Triangulate cobweb spiders typically have the following features:

• Body size: About 3–6 millimeters long
• Leg span: Roughly 20–30 millimeters
• Abdomen pattern: Brown/tan with pale cream or yellow triangular markings
• Cephalothorax: Dark brown to black
• Size difference: Females are noticeably larger than males

They build irregular, tangled cobwebs (not the neat circular “orb” webs) in corners, behind furniture, around utility lines, and near light sources where insects gather.

Common indoor hiding areas include:

• Basements
• Crawl spaces
• Closets
• Bathrooms
• Utility rooms
• Garages

You may also notice small, round egg sacs attached to webbing. Each sac can contain dozens of developing spiderlings, which is one reason webs seem to “multiply” if they aren’t cleaned out regularly.

Are Triangulate Cobweb Spiders Dangerous?

Triangulate cobweb spiders are considered harmless to humans in typical household situations. Bites are uncommon and usually only occur if the spider is accidentally pressed against the skin (for example, in clothing, towels, or stored items). If a bite occurs, reactions are usually mild and localized for most people.

They’re sometimes confused with black widows, but triangulate cobweb spiders typically:

• Have lighter brown coloring
• Lack the distinctive red hourglass marking
• Are smaller in size
• Have much weaker venom than true widow spiders

In many homes, these spiders help reduce nuisance insects by feeding on ants, flies, beetles, and other small pests. If you’re seeing lots of spiders, it’s often a sign there’s an underlying insect food source nearby.

What Do Triangulate Cobweb Spiders Eat?

They feed on insects that become trapped in their sticky webs. Common prey includes:

• Flies
• Mosquitoes
• Ants
• Beetles
• Small moths
• Other spiders

If you’re dealing with ongoing flies or other insects, addressing those pests will often reduce spider activity over time. (See our pest resources section for seasonal prevention guides.)

Where Do They Live? Habitat and Behavior

Triangulate cobweb spiders prefer quiet, undisturbed environments where insects are plentiful. Outdoors, they may hide under rocks, logs, siding, or inside wood piles. Indoors, they occupy dark corners, cluttered spaces, and storage areas that don’t get moved often.

They tend to thrive in:

• Low-traffic areas
• Zones with higher insect activity
• Warm or slightly humid spaces (utility rooms, basements, laundry areas)

Females build messy, three-dimensional webs that look like classic “cobwebs.” These webs act as both shelter and a trap for prey, which is why you’ll often see them tucked behind boxes, shelves, or stored items.

How to Get Rid of Triangulate Cobweb Spiders

If triangulate cobweb spiders are becoming excessive indoors, these steps can help reduce their presence:

1. Remove Their Food Sources

Spiders gather where insects are active. Reducing insects indoors and around the exterior naturally reduces spider numbers. Focus on sanitation, fixing moisture issues, and limiting nighttime insect attraction near doors and windows.

2. Eliminate Webs and Egg Sacs Regularly

• Vacuum webs, egg sacs, and spiders (especially in corners and behind stored items)
• Dust ceiling corners, rafters, and baseboards
• Clean behind furniture and appliances where webs form

3. Reduce Clutter in Storage Areas

Garages, basements, and closets are “spider-friendly” when they’re packed with undisturbed boxes and items. Organizing storage and moving items off floors and away from walls gives spiders fewer places to hide and build webs.

4. Seal Entry Points

Inspect and repair common access points such as:

• Gaps around windows and doors (add weatherstripping or caulk where needed)
• Cracks along foundation walls and siding joints
• Openings around plumbing and utility lines

5. Improve Lighting Strategy and Ventilation

Spiders often show up where insects are drawn in. If exterior lights attract lots of bugs, consider using warmer-toned bulbs and turning off lights when not needed. Improving airflow and addressing damp areas can also make some indoor zones less attractive for both insects and spiders.

6. Use Targeted Pest Control (When Needed)

Broad “spray everything” approaches usually aren’t necessary. If you choose to use store-bought products, always follow the label precisely and focus on cracks/crevices and likely entry points rather than living areas and surfaces people touch.

7. Consider Professional Help

If spider activity is persistent, webs keep returning, or you’re seeing spiders across multiple rooms, professional spider control can identify attractants, reduce food sources, and apply targeted treatments for longer-term results.

Pestcom Pest Management serves homes across the Treasure Valley with spider-focused treatment plans and year-round protection options. If you’d like an inspection, contact us here or call (208) 795-3298.