Cellar Spiders Identification Guide
Pholcus phalangioides
Cellar spiders, often called daddy longlegs spiders, are harmless arachnids commonly found in dark, quiet areas of homes. With their extremely long, thin legs and small bodies, they are frequently mistaken for harvestmen but are true web-building spiders.
Taxonomy
Cellar Spiders Coloration
Common color patterns to help identify cellar spiders
Cellar Spiders
Seasonal Activity
When cellar spiders are most active throughout the year
Cellar Spider Identification Guide
Physical Characteristics
The long-bodied cellar spider (Pholcus phalangioides) is immediately recognizable by its extremely long, thin legs relative to its small body. Adult body length ranges from 6-10mm (approximately 0.24-0.39 inches), but their impressive legspan can reach 30-70mm (1.2-2.8 inches), making them appear much larger than they are.
Their coloring is pale and subtle, typically gray, cream, tan, or light brown. Juveniles often appear translucent. The body consists of a small cephalothorax (head region) and an elongated, cylindrical abdomen. Some individuals display subtle darker markings on the carapace.
Key identification features include:
- Extremely long, thin legs - Often 5-6 times the body length
- Small, elongated body - Cylindrical abdomen, not rounded like house spiders
- Pale coloration - Gray, cream, or tan with translucent quality
- Eight eyes - Arranged in a characteristic pattern
- Hangs upside down - Always found inverted in their irregular webs
Web Characteristics
Cellar spiders build loose, irregular, tangled webs (often called cobwebs) rather than the organized orb webs of garden spiders. These webs are typically found 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
The webs often appear messy and accumulate dust over time. Female cellar spiders carry their egg sacs in their chelicerae (mouthparts) rather than attaching them to the web, which 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) - The most common introduced species, found nationwide in buildings
- Short-bodied Cellar Spider (Spermophora senoculata) - Smaller with a more rounded abdomen
- Marbled Cellar Spider (Holocnemus pluchei) - Found primarily in western states
Cellar Spider Behavior and Biology
Habitat Preferences
Cellar spiders are synanthropic, meaning they have adapted to live in close association with humans. The long-bodied cellar spider (Pholcus phalangioides) is originally from subtropical regions and has spread worldwide through human commerce, thriving in the stable conditions provided by buildings.
They prefer dark, quiet, sheltered locations with adequate humidity:
- Basements and cellars (hence the name)
- Crawl spaces
- Garages and sheds
- Warehouses and storage buildings
- Bathrooms and laundry areas
- Underneath furniture
Unlike many spiders that enter homes seasonally, cellar spider populations often live their entire lives indoors, maintaining stable populations year-round in heated structures.
Diet and Feeding Habits
Cellar spiders are opportunistic predators with a varied diet:
- Flying insects - Mosquitoes, moths, flies, gnats
- Other spiders - They actively prey on other spider species
- Small arthropods - Any creature that becomes trapped in their web
- Conspecifics - They may cannibalize other cellar spiders when food is scarce
Notably, cellar spiders will invade the webs of other spiders to prey on the resident spider. This araneophagic behavior (spider-eating) makes them effective at reducing populations of other spiders, including some that might be more problematic.
Reproduction and Lifecycle
Female cellar spiders exhibit interesting maternal behavior:
- Females produce egg sacs containing roughly 13-60 eggs each
- The egg sac is carried in the mother’s chelicerae until hatching
- Females may produce multiple egg sacs during their lifetime (up to 3 for long-bodied cellar spiders)
- Spiderlings often remain near the mother briefly after hatching
Development includes several molts before maturity, typically taking about one year. Adult cellar spiders can survive up to 2 years in protected indoor environments, making them long-lived among household spiders.
Defensive Behavior
When disturbed, cellar spiders display a characteristic defense mechanism: they rapidly vibrate or gyrate in their web. This behavior:
- Makes the spider appear as a blur, confusing predators
- Helps the spider assess whether web disturbance is from prey or threat
- Can make the spider “disappear” from view through motion blur
This vibrating behavior, combined with their fragile appearance, often startles homeowners but is completely harmless.
Seasonal Activity
Because cellar spiders primarily inhabit indoor environments, their activity differs from outdoor spiders:
- Indoor heated buildings: Medium to high activity year-round (all months)
- Unheated buildings/outdoors: Activity peaks May through September, declines in winter
- Reproduction: Can occur year-round indoors with adequate conditions
In the Mid-Atlantic region and similar temperate climates, indoor populations remain active throughout winter in basements and heated areas.
How We Treat for Cellar Spiders
Cellar spiders require a specialized approach that addresses both the spiders themselves and the conditions that attract them. While they are harmless and even beneficial (by eating other pests), their webs can become unsightly and populations can grow large in favorable conditions.
Our Treatment Process
Step 1: Comprehensive Inspection
We begin by identifying areas of high cellar spider activity and the factors attracting them:
- Examining typical web locations (corners, ceilings, basements)
- Assessing moisture levels and humidity sources
- Identifying prey insect populations
- Locating entry points and harborage areas
- Evaluating exterior lighting that attracts prey 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 are essential because spiders will walk through treated areas without detecting them, resulting in better contact and control.
Step 3: Interior Treatment
For cellar spiders, interior treatment focuses on:
- Spot treatments in high-activity corners and web locations
- Preventative dusting in void areas (particularly effective 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 accessible spider webs around eaves and exterior areas (up to approximately 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 quarterly service plan 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 - Use dehumidifiers in basements and crawl spaces; fix leaks promptly
- Vacuum webs regularly - This directly removes spiders and egg sacs; dispose of vacuum contents outside
- Reduce exterior lighting - Or use yellow “bug lights” that attract fewer prey insects
- Close blinds at night - Prevents interior lights from attracting insects to windows
- Seal entry points - Caulk gaps around windows, doors, and utility penetrations
- Reduce clutter - Eliminate undisturbed corners where webs accumulate
Why Regular Service Matters
While individual cellar spiders are harmless, without regular treatment:
- Populations can grow substantially in favorable conditions
- Dusty, accumulated webs become increasingly unsightly
- Prey insect populations (which attract spiders) are not controlled
- Egg sacs may hatch weeks after initial treatment
Our comprehensive quarterly service maintains the protective barrier, controls prey insects that attract spiders, and includes regular de-webbing to keep your home spider-free.
Safe, Effective Products
We use reduced-risk products that effectively control spiders while prioritizing the safety of your family and pets. Our approach emphasizes targeted applications rather than broad surface spraying, which is ineffective for spider control.
Other Spiders
Explore other species in the spiders family
Commonly Confused With
Cellar Spiders are often mistaken for these similar pests
Where Cellar Spiders Are Found
Hover over states to see their names. Green regions indicate where cellar spiders have been reported.
Common Questions about Cellar Spiders
Are cellar spiders the most venomous spider?
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No, this is a popular myth. While cellar spiders do possess venom to subdue their prey, research has shown their venom is not medically significant to humans. The urban legend that they are extremely venomous but cannot bite humans is false. Their fangs can pierce human skin, but bites are extremely rare and effects are negligible.
Are cellar spiders and daddy longlegs the same thing?
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The term 'daddy longlegs' is confusing because it refers to three different creatures: cellar spiders (true spiders), harvestmen (Opiliones, which are not spiders), and crane flies (insects). Cellar spiders are true spiders that build webs, while harvestmen have a single-segment body and do not produce silk.
Why do cellar spiders vibrate in their webs?
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When disturbed, cellar spiders rapidly vibrate or shake in their webs. This behavior makes them appear blurred and harder for predators to target. It may also help them detect whether something caught in the web is prey or a threat.
Do cellar spiders eat other spiders?
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Yes, cellar spiders are known to prey on other spiders, including potentially dangerous species. They will invade other spiders' webs to capture and consume them. This makes them somewhat beneficial for controlling other spider populations in your home.
How do I get rid of cellar spiders?
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The most effective approach combines regular web removal (vacuuming), reducing humidity and prey insects, sealing entry points, and professional perimeter treatments. Vacuuming webs and egg sacs directly removes spiders and prevents reproduction. Professional treatments focus on exterior barriers and preventative dusting in void areas.
Why are there so many cellar spiders in my basement?
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Cellar spiders prefer dark, damp, undisturbed areas with abundant prey insects. Basements provide ideal conditions with consistent humidity, protected corners for web-building, and plenty of insects attracted to moisture. Reducing humidity and eliminating insect prey will help reduce populations.
Do cellar spiders bite?
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Cellar spider bites are extremely rare. These spiders are not aggressive and will flee or vibrate when disturbed rather than bite. Their first defense is always escape. Even if a bite occurs, it causes only minor, temporary irritation similar to a mosquito bite.
How long do cellar spiders live?
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Cellar spiders can live up to 2 years in protected indoor environments. Females may produce multiple egg sacs during their lifetime, with each sac containing around 13-60 eggs. The spiderlings undergo several molts over approximately one year before reaching maturity.
With five years of hands-on experience in the pest control industry, George Schulz is a registered technician with the Virginia Pest Management Association and a proud third-generation professional in a family business that's been protecting homes for over 57 years. He manages and trains a team of service pros while also leading internal research efforts—recently spearheading a deep-dive review of thousands of documents on pest control materials to hand-pick the most kid and pet friendly, most effective solutions tailored specifically for homes in the DC metro area.