Cellar Spiders Identification Guide

Cellar Spider Identification Guide

Physical Characteristics

The long-bodied cellar spider (Pholcus phalangioides) is easy to spot because of its very long, thin legs and small body. Adults measure 6-10mm in body length, which is about 0.25 to 0.4 inches. Their legspan can reach 30-70mm or 1.2 to 2.8 inches. This makes them look much larger than they really are.

Their color is pale, typically gray, cream, tan, or light brown. Young spiders often appear see-through. The body has a small head region and a long, tube-shaped abdomen. Some have faint darker markings on their backs.

Key identification features include:

• Very long, thin legs that are 5-6 times the body length
• Small, tube-shaped body that is not rounded like house spiders
• Pale color in gray, cream, or tan, often somewhat see-through
• Eight eyes in a grouped pattern
• Hangs upside down in their messy, tangled webs

Web Characteristics

Cellar spiders build loose, messy, tangled webs often called cobwebs. Unlike garden spiders, they do not make neat circular webs. You can usually find their webs in:

• Upper corners of rooms, especially ceilings
• Basement ceilings and floor joists
• Crawl spaces and cellars
• Garage corners and eaves
• Behind water heaters and in utility areas
• Window corners and door frames

These webs often look messy and collect dust over time. Female cellar spiders carry their egg sacs in their mouths rather than attaching them to the web. This behavior is unusual among spiders.

Common Species in North America

The family Pholcidae includes several species commonly found in homes:

• Long-bodied Cellar Spider (Pholcus phalangioides) is the most common species. It is found in buildings across North America.
• Short-bodied Cellar Spider (Spermophora senoculata) is smaller with a more rounded body.
• Marbled Cellar Spider (Holocnemus pluchei) is found mainly in western states.

Cellar Spider Behavior and Biology

Habitat Preferences

Cellar spiders have adapted to live close to humans. The long-bodied cellar spider (Pholcus phalangioides) came from warm regions. It has spread worldwide and now thrives in the stable conditions found in buildings.

They prefer dark, quiet, sheltered spots with some humidity:

• Basements and cellars, which is how they got their name
• Crawl spaces
• Garages and sheds
• Warehouses and storage buildings
• Bathrooms and laundry areas
• Underneath furniture

Unlike many spiders that enter homes only at certain times of year, cellar spiders often live their entire lives indoors. They can maintain stable populations year-round in heated buildings.

Diet and Feeding Habits

Cellar spiders eat whatever gets caught in their webs:

• Mosquitoes, moths, flies, and gnats
• Other spiders, which they actively hunt
• Small bugs of any kind that get trapped
• Other cellar spiders when food is scarce

Cellar spiders will also invade the webs of other spiders to prey on them. This spider-eating behavior can reduce populations of other spiders in your home.

Reproduction and Lifecycle

Female cellar spiders show interesting mothering behavior:

• Females produce egg sacs with 13-60 eggs each
• The mother carries the egg sac in her mouth until the eggs hatch
• Females can produce up to 3 egg sacs in their lifetime
• Baby spiders often stay near the mother for a short time after hatching

Young spiders go through several molts before becoming adults, which takes about one year. Adult cellar spiders can live up to 2 years indoors, longer than most household spiders.

Defensive Behavior

When disturbed, cellar spiders shake rapidly in their webs. This defense behavior:

• Makes the spider look like a blur, confusing predators
• Helps the spider tell if something in the web is food or a threat
• Can make the spider seem to disappear through motion blur

This shaking, along with their delicate look, often startles homeowners. However, it is completely harmless.

Seasonal Activity

Because cellar spiders live mainly indoors, their activity is different from outdoor spiders:

• In heated buildings, they have medium to high activity all year
• In unheated buildings or outdoors, they are most active May through September and less active in winter
• Reproduction happens year-round indoors when conditions are right

In the Mid-Atlantic region and similar climates, indoor populations stay active through winter in basements and heated areas.

How We Treat for Cellar Spiders

Cellar spiders need a targeted approach that addresses both the spiders and the conditions that attract them. Their webs can become unsightly, and populations can grow large when conditions are right.

Our Treatment Process

Step 1: Comprehensive Inspection

We begin by identifying areas of high cellar spider activity and the factors attracting them:

• Checking where webs are found, such as corners, ceilings, and basements
• Checking moisture levels and sources of humidity
• Finding what insects are present that spiders eat
• Finding entry points and hiding spots
• Looking at exterior lighting that attracts insects

Step 2: Exterior Barrier Treatment

We apply a non-repellent spray to exterior areas where spiders may enter or build webs:

• Window frames and doorways
• Foundation perimeter
• Eaves and soffits
• Utility penetrations
• Areas where webs are commonly found

Non-repellent products work best because spiders walk through treated areas without detecting them. This leads to better contact and control.

Step 3: Interior Treatment

For cellar spiders, interior treatment focuses on:

• Spot treatments in high-activity corners and web locations
• Dusting in hidden void areas, which works very well for cellar spiders
• Treatment around entry points and utility penetrations
• Basements, crawl spaces, and other preferred habitats

Step 4: Web and Egg Sac Removal

We remove spider webs around eaves and exterior areas up to about 6-8 feet high. Regular web removal:

• Directly eliminates spiders and egg sacs
• Discourages rebuilding in the same locations
• Reduces visual nuisance of accumulated webbing

Step 5: Ongoing Maintenance

Our tri-annual service plan, which is three times per year, provides continued protection:

• Reapplication of exterior barrier treatments
• De-webbing as needed
• Monitoring of spider activity levels
• Addressing new concerns as they arise

Customer Guidance

For best results, we recommend these complementary measures:

• Reduce humidity by using dehumidifiers in basements and crawl spaces. Fix leaks promptly.
• Vacuum webs regularly to directly remove spiders and egg sacs. Dispose of vacuum contents outside.
• Reduce exterior lighting or use yellow “bug lights” that attract fewer insects.
• Close blinds at night to prevent interior lights from attracting insects to windows.
• Seal entry points by caulking gaps around windows, doors, and pipes.
• Reduce clutter to eliminate undisturbed corners where webs build up.

Why Regular Service Matters

Without regular treatment:

• Populations can grow quickly when conditions are good
• Dusty, built-up webs become unsightly
• Prey insect populations that attract spiders are not controlled
• Egg sacs may hatch weeks after initial treatment

Our tri-annual service maintains the protective barrier and controls prey insects that attract spiders. It also includes regular de-webbing to keep your home spider-free.

Tested Treatment Strategies

We use EPA-approved products that effectively control spiders. These are products we feel comfortable using in our own homes. We focus on targeted applications instead of broad surface spraying, which does not work well for spider control.

References

• Penn State Extension. Longbodied Cellar Spider. https://extension.psu.edu/longbodied-cellar-spider
• National Pest Management Association. Long-bodied Cellar Spiders. https://www.pestworld.org/pest-guide/spiders/long-bodied-cellar-spiders/
• UC Agriculture and Natural Resources. Spider Management Guidelines. https://ucanr.edu/pest-notes/spiders