(208) 297-7947

Spiders & Scorpions

Yellow Sac Spider

Cheiracanthium species

Danger Level: 3/5Updated September 2026 · Boise, ID

IdentificationHow to Identify Yellow Sac Spider

Quick Answer

Yellow sac spiders are small (5-10mm) pale yellow to light green spiders with slightly darker jaws. They build small silk "sacs" or tubes in corners rather than traditional webs.

Full identification notes

They're nocturnal hunters found on walls and ceilings at night.

Get Help Now
Spider Management

  • Free

    Re-Service Between Visits

  • 4.9/5

    Google Rating

  • 9 to 5

    Office Hours, Mon to Fri

Yellow Sac Spider Behavior & Habits

Understanding how yellow sac spider behave helps prevent infestations

Yellow sac spiders are active hunters, not web-builders.

More about their habits

They spin silken sacs in corners and crevices where they hide during the day, then wander walls and ceilings at night looking for prey. They're behind more bites than any other spider species in the US, mostly because they end up trapped against skin in clothing or bedding.

Yellow Sac Spider Risks & Dangers

What yellow sac spider can do to your health and property

Health Risks

Yellow sac spider bites are more common than black widow bites and leave a noticeable spot of pain, redness, and swelling.

Property Damage

No structural damage, though the silken sacs in upper corners and behind picture frames are unsightly and tough to clean.

Full health and property details

Health Risks

A small share of bites turn into slow-healing wounds. Bites aren't life-threatening, but they're painful and worth a doctor visit if the area keeps spreading after a day or two.

Signs of Yellow Sac Spider Infestation

Look for these indicators in your home

Signs You Have Yellow Sac Spider

What homeowners spot first

  1. Small silken sacs in wall/ceiling corners
  2. Pale yellowish spiders on walls at night
  3. Spiders dropping from ceiling or walls
More signs to look for
  1. Bite wounds appearing overnight
  2. Small tubes of silk behind pictures or furniture

Yellow Sac Spider in Boise & the Treasure Valley

In our years across the Treasure Valley, we see yellow sac spider calls peak from July through October in Boise, Meridian, and Eagle.

More on what we see locally

They cause more nighttime bites here than any other spider, often catching folks asleep or fishing clothes off the bedroom floor.

Our Solution

How We Handle Yellow Sac Spider

What our approach looks like

Yellow sac spider control means treating the wall and ceiling junctions, the backs of pictures, and the crack-and-crevice harbors where they spin their daytime sacs.

Our full approach

We pair that with a full exterior perimeter spray so the next batch can't walk in from outside. New customers start at $49 for the initial service, and our free re-service guarantee covers any callbacks between visits.

Learn About Our Spider Management

How to Prevent Yellow Sac Spider

Steps you can take to reduce the risk of infestation

  1. Shake out clothes, shoes, and bedding before use
  2. Pull beds and couches a few inches off the walls
  3. Clear clutter and storage boxes from along baseboards
More prevention steps
  1. Seal cracks around window trim, baseboards, and ceiling corners
  2. Vacuum sacs and egg pouches whenever you spot them
  3. Swap white exterior lights for yellow bug-bulbs to cut nighttime prey

Yellow Sac Spider Questions Answered

Common questions about identification, prevention, and treatment

Call (208) 297-7947

Why do yellow sac spiders bite so often?

Quick answerYellow sac spiders are nighttime wanderers that crawl across beds, walls, and floors looking for prey.

Bites happen when one gets trapped against skin in bedding or a shirt sleeve, and the spider bites in self-defense. They're not aggressive, just startled by sudden pressure.

Are yellow sac spider bites dangerous?

Quick answerFor most healthy adults, no.

You'll feel a sharp pinch, then localized pain, redness, and swelling for a few days, similar to a wasp sting. A small share of bites develop slow-healing ulcers, so if the spot keeps spreading or oozing 48 hours in, see a doctor. Bites are never fatal, but kids and immunocompromised folks should be watched more closely.

How do I keep yellow sac spiders out of my bedroom?

Quick answerPull the bed a few inches off the wall so spiders can't drop onto it overnight, keep clothes off the floor, and shake out anything that's been sitting.

Vacuum the upper corners of the room and behind picture frames once a week to break up sacs. We also treat ceiling junctions and baseboards inside the bedroom on request as part of our $49 initial service.

Think You Have Yellow Sac Spider?

Call and we'll talk through your options. We usually get out within 24 to 48 hours.

Quarterly plans starting at

$119/quarter

  • No-Obligation Quote
  • Locally Owned
  • Free Re-Service Between Visits

Call Now

Or call now: (208) 297-7947

(208) 297-7947

Our Pest Control Services

Complete pest protection. Professional solutions for every pest problem, on a quarterly plan or a one-time visit.

View All Services

Proudly Serving the Treasure Valley

Local technicians from the Treasure Valley, in Boise, Meridian, and surrounding communities.

View All Service Areas

Pest Control Resources

Expert tips & guides. Local pest knowledge from Boise's trusted exterminators