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Spiders & Scorpions

Cellar Spider (Daddy Long Legs)

Pholcus phalangioides

Danger Level: 1/5Updated September 2026 · Boise, ID

IdentificationHow to Identify Cellar Spider (Daddy Long Legs)

Quick Answer

Cellar spiders have small tan bodies (6-9mm) with extremely long, thin legs that can span 50mm or more. They build loose, irregular webs in corners and hang upside down.

Full identification notes

When disturbed, they vibrate rapidly in their web. That defensive behavior is called "whirling."

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Cellar Spider (Daddy Long Legs) Behavior & Habits

Understanding how cellar spider (daddy long legs) behave helps prevent infestations

Cellar spiders build messy, tangled webs in undisturbed areas and hang upside down waiting for prey.

More about their habits

They're known to prey on other spiders, including black widows and hobo spiders. Old webs accumulate as they build new ones nearby rather than repairing damaged webs.

Cellar Spider (Daddy Long Legs) Risks & Dangers

What cellar spider (daddy long legs) can do to your health and property

Health Risks

Cellar spiders are completely harmless to humans.

Property Damage

The main issue is unsightly accumulations of old webbing in corners and ceilings.

Full health and property details

Health Risks

The myth that they're "most venomous but can't bite" is false. They can bite but rarely do, and their venom has no significant effect on humans.

Signs of Cellar Spider (Daddy Long Legs) Infestation

Look for these indicators in your home

Signs You Have Cellar Spider (Daddy Long Legs)

What homeowners spot first

  1. Loose, tangled webs in corners
  2. Spiders hanging upside down in webs
  3. Spiders vibrating rapidly when disturbed
More signs to look for
  1. Accumulated old webs in undisturbed areas
  2. Very long, thin-legged spiders

Cellar Spider (Daddy Long Legs) in Boise & the Treasure Valley

Cellar spiders show up in a lot of the Treasure Valley basements and garages we service, especially unfinished basements across the North End, Eagle, Meridian, and Kuna.

More on what we see locally

Calls pick up in late summer and early fall when Boise homeowners start storing things in the garage and finally notice the cobweb buildup. The good news: these spiders quietly hunt black widows and hobo spiders, so most of our cellar spider work in 2026 has been web cleanup and humidity advice, not knockdown.

Our Solution

How We Handle Cellar Spider (Daddy Long Legs)

What our approach looks like

Our $49 initial service for cellar spiders focuses on physical web removal in basements, garages, and eaves, plus a residual perimeter treatment that knocks down the prey insects they feed on.

Our full approach

We don't aggressively target the spiders themselves because they're beneficial predators of black widows and hobo spiders. Quarterly visits keep the webs from rebuilding without removing one of the better natural controls in your home.

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How to Prevent Cellar Spider (Daddy Long Legs)

Steps you can take to reduce the risk of infestation

  1. Vacuum webs and egg sacs quarterly in basements, garages, and crawlspaces
  2. Run a dehumidifier to keep basement humidity below 50 percent
  3. Seal cracks around foundation vents, rim joists, and basement windows
More prevention steps
  1. Reduce outdoor lighting near doors to cut down on the prey insects they eat
  2. Clear clutter and stored boxes off basement and garage floors
  3. Schedule a quarterly perimeter treatment to thin the insect prey base

Cellar Spider (Daddy Long Legs) Questions Answered

Common questions about identification, prevention, and treatment

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Are daddy long legs the most venomous spider in the world?

Quick answerNo, that's a popular myth.

Cellar spiders can bite and their venom is not particularly potent. They're completely harmless to humans and actually prey on dangerous spiders like black widows and hobo spiders.

Should I kill cellar spiders in my Boise basement?

Quick answerWe usually recommend leaving them alone if you can tolerate the webs.

Cellar spiders are one of the most useful predators a Treasure Valley basement can host. They eat black widows, hobo spiders, and other pests we get calls about every week. Knock down the old webs with a vacuum and you remove the eyesore without losing the benefit.

Why do I have so many cellar spider webs in my garage and crawlspace?

Quick answerTwo reasons.

First, cellar spiders never repair old webs, so layers build up year after year in any spot a broom doesn't reach. Second, Treasure Valley basements and crawlspaces hold steady humidity and a quiet food supply of small insects, which is exactly what they want. A dehumidifier set to 50 percent and a quarterly vacuum sweep cuts populations fast.

How does Green Guard handle cellar spiders during a regular service?

Quick answerOur $49 initial service includes a full eave and corner web sweep, and we apply a residual perimeter treatment that keeps prey insects from feeding them.

We don't aggressively target the spiders themselves because they're beneficial. Most subscribers see web buildup drop sharply after the first or second visit.

Think You Have Cellar Spider (Daddy Long Legs)?

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

Quarterly plans starting at

$119/quarter

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