Cellar Spider (Daddy Long-Legs)
Pholcus phalangioides
The cellar spider is among the most common spider species found in commercial premises across the Windsor-Essex region, particularly in basements, mechanical rooms, stairwells, and loading areas.
While harmless, visible cobwebs and hanging spiders are an aesthetic and sanitation concern in food service, retail, and healthcare environments.
Its tendency to accumulate old, dusty webs over time can contribute to an impression of poor facility maintenance and may attract regulatory attention during inspections.
Habitat
Found throughout commercial buildings in any space that is cool, somewhat humid, and infrequently disturbed.
Common locations include stairwell corners, basement mechanical rooms, the undersides of loading dock structures, boiler rooms, crawl space entrances, and storage rooms with low foot traffic. In multi-story buildings it is most abundant in the lowest levels.
Active Areas
Windsor
Ubiquitous in basements, garages, and undisturbed building areas throughout the city. Found in virtually all occupied buildings.
Tecumseh
Common across all residential and commercial property types. Suburban homes with finished and unfinished basements are heavily colonised.
LaSalle
Universal presence across the municipality. Properties with higher basement humidity tend to have denser populations.
Amherstburg
Very common throughout, including in older homes and commercial buildings. Riverside properties with higher humidity see elevated populations.
Lakeshore
Common across the municipality in all building types. Agricultural outbuildings are heavily colonised.
Essex
Common in residential and commercial buildings throughout the town and surrounding area.
Kingsville
Ubiquitous in basements and undisturbed areas. Greenhouse-adjacent properties may see elevated numbers due to higher ambient humidity.
Leamington
Universal presence in basements and low-traffic areas across the municipality. The region's generally higher humidity supports robust populations year-round.
Chatham-Kent
High prevalence. Cellar spiders are extremely common in basements, garages, and outbuildings across Chatham-Kent.
St. Thomas
High prevalence. Virtually ubiquitous in undisturbed basement and garage corners in St. Thomas homes.
Seasonality
Year-round activity in all climate-controlled commercial premises. In unheated or partially heated structures, activity slows in mid-winter but rarely ceases.
Web accumulation is a continuous process in undisturbed areas. Routine web removal during scheduled cleaning is the most effective way to manage the population’s visual impact.
Spring
Summer
Autumn
Winter
Appearance
The appearance in commercial settings is identical — a small pale body suspended on extraordinarily long slender legs in a loose web in a corner or ceiling junction. In dim storage areas or mechanical rooms the spider can be hard to see until the web itself is spotted.
Old, dust-covered webs from cellar spiders are a persistent feature of neglected corners in commercial buildings and are among the most common web types found during pest inspections.
- Extraordinarily long, slender, fragile-looking legs — typically 5–6 times the body length
- Small, oval, pale grey to tan body with a subtle darker mark on the cephalothorax
- Builds a loose, irregular, three-dimensional web in corners of basements, cellars, and garages
- Vibrates rapidly in its web when disturbed, making itself appear as a blur
- Female carries egg clutch loose in her chelicerae (jaws) rather than in a silk sac
Behaviour
In commercial settings the spider’s passive, web-bound lifestyle means it poses no risk to staff or customers. Its primary commercial impact is aesthetic — accumulating dusty, multi-layered webs in corners over time.
It will prey on other spider species within a facility, which provides some incidental pest-suppression benefit. Vibration behaviour when webs are disturbed during inspections can be startling but is harmless.
Lifecycle
Egg
The distinctive egg-carrying behaviour — female holding a small cluster of eggs in her jaws — is an identifiable sign of active reproduction in a facility.
Unlike egg sacs attached to a web, these eggs move with the female, making them harder to locate during inspections. A gravid female discovered during a commercial inspection indicates an established, actively reproducing population rather than an occasional intruder.
Spiderling
Spiderlings that hatch in a commercial facility will typically remain in the same zone as the mother unless disturbed. In basements and storage rooms, multiple size classes of cellar spiders are often present simultaneously, indicating a self-sustaining breeding population.
Regular web removal disrupts this cycle by exposing and removing individuals at all life stages.
Adult
Long-lived adults in commercial settings are the primary source of web accumulation. A single adult cellar spider in a corner can produce a substantial, dusty, multi-layered web structure over the course of months.
In facilities where cleaning does not reach ceiling corners and behind fixed equipment, these webs can become quite prominent. Regular professional pest service should include web removal from all areas including hard-to-reach ceiling junctions.
Signs You May Have a Problem
- Persistent dusty, multi-layered cobwebs in the corners of stairwells, mechanical rooms, basement storage, and loading dock structures
- Pale, long-legged spiders hanging in loose webs in ceiling-wall junctions and behind fixed equipment in low-traffic areas
- Females carrying small loose egg clusters in their jaws — a reliable indicator of active in-facility reproduction
- Webs found behind shelving, under fixed equipment, and in ceiling corners during inspection that are not being cleaned regularly
- Increasing web density in areas adjacent to insect entry points, particularly around drains, utility penetrations, and poorly sealed windows
- Multiple spiders and webs at different life stages present simultaneously, indicating a self-sustaining population
Risks & Concerns
Not a health hazard to staff or the public. However, in food service, retail, or healthcare environments, visible cobwebs — particularly dusty, multi-layered webs in corners — can trigger hygiene citations, failed audits, and customer complaints.
Regular web removal is a sanitation requirement in these environments regardless of the spider’s harmless nature. Persistent reinfestation may signal inadequate structural exclusion or unresolved moisture issues.
Prevention
- Incorporate web removal from all basement, mechanical room, and stairwell corners into the regular facility cleaning schedule — document completion
- Conduct quarterly professional spider inspections of all low-traffic areas, including behind fixed equipment and in ceiling junctions
- Address moisture issues and improve ventilation in basements and mechanical rooms to reduce population-supporting conditions
- Seal structural penetrations and gaps around pipes and conduits that provide entry points from outside
- Ensure cleaning equipment (cobweb brushes on extension poles) is available and used in all areas including high ceiling corners
DIY Control
- Assign web-removal responsibility to cleaning staff with a documented schedule covering all basement and low-traffic areas
- Use long-handled cobweb brushes to reach ceiling corners and behind fixed equipment
- Apply appropriately labelled residual products during off-hours following all regulatory and safety requirements
- Monitor with sticky traps and record counts to track population trends over time
Professional Control
- Scheduled professional web-removal and residual insecticide service covering all basement, mechanical, and storage areas
- Documented treatment records suitable for regulatory audit
- Moisture and ventilation assessment with written recommendations
- Exclusion service for key structural entry points
- Ongoing monitoring with sticky traps and written inspection reports at each visit