Woodlouse Spiders: Identification & Control Guide for Homeowners

My basement flashlight caught something unusual scuttling across the concrete floor last spring.

A reddish-brown spider with disproportionately large jaws froze in my beam.

After three years of helping homeowners identify pests, I knew this was a woodlouse spider (Dysdera crocata).

Woodlouse spiders are distinctive hunting spiders named for their specialized diet of woodlice, and while they look intimidating with their large fangs, these spiders pose minimal danger to humans and actually help control pill bug populations around your home.

In this guide, I'll walk you through everything you need to know about identifying, understanding, and managing woodlouse spiders safely.

What Are Woodlouse Spiders?

Woodlouse spiders, scientifically known as Dysdera crocata, are medium-sized hunting spiders recognized by their reddish-brown coloration and unusually large jaws.

These spiders belong to the family Dysderidae and have earned the nickname "woodlouse hunters" because their primary prey consists of woodlice (also called pill bugs, roly polies, or isopods).

Unlike most spiders that spin webs to catch prey, woodlouse spiders are active hunters that seek out their food in dark, damp environments.

Physical Identification Features

Identifying a woodlouse spider correctly matters because many homeowners confuse them with more dangerous species like brown recluse spiders.

Feature	Woodlouse Spider	Brown Recluse (for comparison)
Color	Reddish-brown legs and cephalothorax, cream-colored abdomen	Uniform tan to brown
Eyes	Six eyes in tight oval pattern	Six eyes in three pairs (dyad arrangement)
Size	Body length 0.4-0.6 inches	Body length 0.25-0.5 inches
Jaws/Fangs	Large, forward-facing, reddish	Small, not prominently visible
Violin marking	Absent	Present on cephalothorax

The most distinctive feature of woodlouse spiders is their large, forward-projecting jaws (chelicerae) that look disproportionate to their body size.

These powerful jaws evolved to pierce and crush the hard armored shells of woodlice, which make up nearly their entire diet.

Eye Arrangement

Woodlouse spiders have six eyes arranged in a compact oval or kidney-shaped pattern on the front of their head.

This eye arrangement differs from many other spider species and serves as a key identification characteristic when you're examining them closely.

Behavior and Habitat

Woodlouse spiders are nocturnal hunters that become active at night to search for prey.

During daylight hours, they hide in dark, sheltered locations such as under stones, logs, leaf litter, and in the damp corners of basements and crawlspaces.

Do They Build Webs?

Unlike web-building spiders like cellar spiders or orb weavers, woodlouse spiders do not spin webs to catch their prey.

Instead, they actively hunt down woodlice using their excellent sensitivity to vibrations and chemical cues.

When they find a woodlouse, they use those powerful jaws to pierce the armored exoskeleton and inject venom that liquefies the prey's insides.

Preferred Habitats

These spiders thrive wherever woodlice are abundant, which means any damp, dark environment with organic debris.

• Outdoor locations: Under rocks, logs, leaf litter, and in compost piles
• Indoor locations: Basements, crawlspaces, ground-level floors, and bathrooms
• Entry points: Ground-level cracks, gaps around pipes, foundation vents

I've found most woodlouse spider activity in homes occurs near where moisture problems exist, since damp conditions attract both the spiders and their woodlice prey.

Are Woodlouse Spiders Dangerous?

The short answer is no, woodlouse spiders are not considered dangerous to humans.

While these spiders do possess venom and can bite if handled roughly or trapped against skin, their venom is not medically significant to people.

Their large jaws look intimidating but evolved specifically for crushing woodlice shells, not for defending against large predators like humans.

Bite Information

Woodlouse spider bites are rare and typically occur only when the spider is accidentally trapped against bare skin or deliberately handled.

When bites do occur, symptoms are usually mild and similar to a bee sting or mosquito bite.

Aspect	Details
Pain level	Mild to moderate, sharp initial pain
Duration	Usually subsides within 1-2 hours
Visible signs	Redness, slight swelling at bite site
Systemic effects	None reported in medical literature
Medical attention	Rarely needed unless infection develops

If you experience severe pain, spreading redness, or signs of infection after any spider bite, seek medical attention promptly.

Pet Safety Considerations

Many homeowners ask about pet safety when discovering woodlouse spiders.

Woodlouse spider venom is not considered dangerous to dogs or cats, though a bite to a curious pet might cause localized pain or swelling similar to a bee sting.

Cats and dogs are much more likely to be bitten by bees or wasps than by woodlouse spiders, since these spiders generally avoid confrontation and flee when possible.

Signs of Woodlouse Spider Activity

How do you know if you have woodlouse spiders around your home?

The most obvious sign is actually seeing the spiders themselves, typically at night when they're hunting.

Common Sighting Locations

• Basements: Along foundation walls, in corners, near floor drains
• Crawlspaces: Under insulation, around pier beams
• Ground-floor bathrooms: Around sinks, tubs, toilets
• Garages: Near doors, under stored items

Presence of Woodlice

Finding woodlice (pill bugs, roly polies) in or around your home often indicates conditions favorable to woodlouse spiders.

Since woodlice are their primary food source, where you find woodlice, woodlouse spiders often follow.

Normal vs. Problematic Activity

Seeing an occasional woodlouse spider, especially in spring or fall when they're most active, is normal and not cause for alarm.

However, regular sightings of multiple spiders might indicate moisture issues or woodlice problems that should be addressed.

Preventing Woodlouse Spiders

The most effective way to prevent woodlouse spiders is to make your home less attractive to both the spiders and their woodlice prey.

After treating homes across four different climate zones, I've found that moisture control is the single most important factor in long-term spider prevention.

Moisture Control

Woodlice thrive in damp conditions, and woodlouse spiders follow their food source.

1. Fix leaks promptly: Repair dripping faucets, leaking pipes, and roof leaks
2. Improve ventilation: Install exhaust fans in bathrooms and kitchens
3. Use dehumidifiers: Target basements and crawlspaces, keeping humidity below 50%
4. Extend downspouts: Direct rainwater at least 6 feet away from your foundation

Sealing Entry Points

Physical exclusion prevents spiders from entering your home in the first place.

• Caulk cracks: Seal foundation cracks, gaps around pipes, and utility penetrations
• Install door sweeps: Add weatherstripping to all exterior doors
• Repair screens: Ensure window screens fit tightly and have no tears
• Vent covers: Install mesh covers (1/8 inch or smaller) on foundation vents

Removing Clutter and Harborage

Both woodlice and woodlouse spiders need shelter during the day.

Remove potential hiding spots by storing items off the floor, eliminating cardboard boxes on concrete, and keeping storage areas organized.

Addressing the Woodlice Problem

Since woodlice are the primary food source, reducing their population naturally reduces woodlouse spider activity.

Remove organic debris from near your foundation, stack firewood away from the house, and ensure proper drainage to discourage woodlice from taking up residence.

Seasonal Prevention Calendar

Different seasons require different prevention strategies.

This seasonal approach has helped my clients maintain spider-free homes year after year.

Season	Priority Tasks
Spring	Inspect foundation for winter damage, clean gutters, repair screens, apply preventive barrier spray, reduce outdoor clutter
Summer	Maintain dehumidifier in basement, monitor moisture levels, keep vegetation trimmed away from foundation
Fall	Seal cracks before winter, install door sweeps, check weatherstripping, remove leaf litter from foundation
Winter	Monitor indoor humidity, check for new moisture issues, inspect areas where pipes enter home

Fall is particularly important because spiders seek shelter as temperatures drop, making September and October prime times for spider invasions.

Top Products for Woodlouse Spider Control

After researching and testing various control methods, I've identified five products that effectively address woodlouse spider problems.

The right product depends on your specific situation, whether you need quick knockdown, long-term prevention, or pet-safe options.

1. Black Flag Spider and Scorpion Killer - Best Fast-Knockdown Spray

This aerosol spray delivers fast results when you need immediate spider control.

The 5-foot spray range lets you maintain distance from spiders while applying treatment, which matters when you're dealing with any spider in tight spaces.

I've used this product for spot treatments in basements and garages where woodlouse spiders congregate near foundation walls.

The formula paralyzes spiders on contact and even kills black widow spiders as they hatch, addressing egg sacs that might otherwise produce future generations.

Customer photos show the product effectively clearing spider-infested corners within days of application.

The 12-pack configuration offers excellent value for homeowners dealing with recurring spider problems or larger properties requiring multiple treatment areas.

Who Should Buy?

Choose this spray if you need immediate spider knockdown and want a product you can use both indoors and outdoors without mixing or special equipment.

Who Should Avoid?

Skip this aerosol if you prefer long-term residual protection or need pet-safe alternatives for high-traffic areas.

2. RESCUE! Spider Traps - Best Non-Toxic Monitoring

These glue traps offer a chemical-free approach to spider control that works well for monitoring and reducing populations.

The double-sided design doubles the lifespan of each trap, simply flip it over when one side becomes full.

I recommend placing these traps along baseboards, behind furniture, and in corners where spiders typically travel.

The decorative plastic shell helps the traps blend with home decor, which matters if you prefer not to have obvious pest control products visible in living areas.

Customer images demonstrate the traps catching multiple spider species including brown recluse, wolf spiders, and black widows in addition to woodlouse spiders.

These traps work best as part of an integrated approach, helping you identify spider hotspots while reducing populations without chemicals.

Who Should Buy?

Pet owners and parents will appreciate these non-toxic traps that pose no chemical risk to children or animals.

Who Should Avoid?

Look elsewhere if you need immediate elimination of an established spider population or prefer barrier prevention methods.

3. Wet & Forget Miss Muffet's Revenge - Best Long-Lasting Barrier

This residual spray creates a barrier that keeps spiders away for up to 12 months with a single application.

The attached sprayer reaches up to 10 feet, letting you treat high areas like eaves and ceiling corners without needing a ladder.

Bifenthrin, the active ingredient, provides long-lasting residual protection that continues working months after application.

I've found this product particularly effective around foundation exteriors, door frames, and window casings where spiders typically enter homes.

The formula is ready to use with no mixing required, and the 64-ounce container covers substantial area for comprehensive treatment.

Customer feedback consistently shows significant reduction in spider activity within weeks of application, with effects lasting through multiple seasons.

Who Should Buy?

Homeowners wanting long-term prevention without frequent reapplication will appreciate the 12-month protection this product provides.

Who Should Avoid?

This product is not labeled for black widow or brown recluse spiders, so choose different products if you're dealing with those dangerous species.

4. HARRIS Diatomaceous Earth - Best Natural Option

Food-grade diatomaceous earth offers a completely natural way to control spiders and their woodlice prey.

The powder works mechanically, absorbing the waxy outer layer of insects and causing dehydration, rather than using chemical insecticides.

The included powder duster makes application straightforward in cracks, crevices, and voids where spiders hide during daylight hours.

Since DE is effective against woodlice, using it addresses both the prey and predator in one treatment.

Customer photos show effective application along baseboards, behind appliances, and in crawlspaces where moisture attracts spider populations.

This product remains effective as long as it stays dry, making it ideal for indoor use in protected areas.

Who Should Buy?

Eco-conscious homeowners and those seeking chemical-free pest control will appreciate this natural, OMRI-listed option.

Who Should Avoid?

DE becomes ineffective when wet, so avoid this product in damp areas or outdoor locations exposed to rain unless you're willing to reapply frequently.

5. Ortho Home Defense Insect Killer - Best Perimeter Treatment

This perimeter treatment creates a barrier around your home's interior and exterior foundation.

The 1.33-gallon refill size provides substantial product for treating larger homes or multiple applications throughout the season.

Ortho's formula targets multiple pests including spiders, ants, and roaches, addressing various entry points and food sources that attract spiders.

Apply around door frames, windows, and along foundation walls both inside and outside for comprehensive protection.

Who Should Buy?

Budget-conscious homeowners needing coverage for multiple pest types will appreciate this versatile, affordable option.

Who Should Avoid?

Consider other options if you need pet-safe products or prefer natural alternatives to synthetic insecticides.

Comparison Table: Spider Control Products

Product	Type	Best For	Pet Safe	Duration
Black Flag Spider Killer	Aerosol spray	Fast knockdown	When dry	Immediate
RESCUE! Spider Traps	Glue traps	Non-toxic monitoring	Yes	Until full
Miss Muffet's Revenge	Residual spray	Long-term barrier	When dry	Up to 12 months
HARRIS Diatomaceous Earth	Powder	Natural treatment	Yes	Until wet
Ortho Home Defense	Perimeter spray	Multi-pest barrier	When dry	Seasonal

When to Call a Professional?

Most woodlouse spider situations can be handled with DIY methods and the products recommended above.

However, professional help becomes necessary in certain circumstances.

Professional pest control costs typically range from $150-500 for initial treatment, with quarterly maintenance plans averaging $75-150 per visit.

Frequently Asked Questions

Final Recommendations

After working with dozens of homeowners facing woodlouse spider concerns, I've found that an integrated approach works best.

Start with identification and exclusion: seal cracks, reduce moisture, and remove clutter to make your home less attractive to both spiders and their prey.

For active spider problems, combine RESCUE! traps for monitoring with either Miss Muffet's Revenge for long-term barriers or Black Flag for immediate knockdown.

Remember that woodlouse spiders are beneficial predators that help control woodlice populations, so complete elimination isn't always necessary or desirable.

Focus on prevention and management rather than eradication, and you'll achieve better long-term results with fewer chemicals.