Why Do Spiders Come Inside? Understanding Spider Entry

Understanding why spiders enter your home is the key to keeping them out. While the knee-jerk reaction is to kill every spider you see, addressing the underlying causes is far more effective than reactive treatments.

The Top Reasons Spiders Come Inside

1. Following Prey Insects

This is the number one reason spiders appear indoors. If your home has flies, moths, gnats, mosquitoes, or other small insects, spiders will follow the food supply. A home full of prey insects is a spider buffet.

Solution: Address your insect problem first. Fix window screens, keep food sealed, clean regularly, and manage moisture that attracts insects. When the insects disappear, most spiders will too.

2. Seeking Shelter

Spiders prefer sheltered, undisturbed spaces for building webs, hunting, and laying eggs. Cluttered basements, packed garages, messy closets, and rarely cleaned corners all provide ideal spider habitat.

Solution: Reduce clutter, especially in storage areas. Store items in sealed plastic bins. Keep a clean perimeter along walls. Vacuum regularly.

3. Weather Events

Rain

Heavy rain floods ground-level spider hiding spots — burrows, leaf litter, ground cover — forcing ground-dwelling species like wolf spiders to seek higher, drier ground, which often means your home.

Cold Weather

As winter approaches, falling temperatures push spiders and their prey indoors. Many spiders you see inside during fall are not entering your home — they have been there all along but become more visible during mating season when males wander in search of females.

Heat and Drought

Extreme heat and dry conditions can also drive spiders toward the cooler, more humid environment inside your home.

Solution: Seal entry points before weather events push spiders inside. The best time to weatherproof is late summer, before fall spider activity peaks.

4. Mating Season

In fall, male spiders of many species leave their webs and hiding spots to search for females. This wandering behavior dramatically increases indoor spider sightings. The spiders are not entering your home to set up permanent residence — they are passing through on their mating journey.

Solution: Fall is temporary. Increased sightings during September and October are normal and will decrease as mating season ends. Use sticky traps to intercept wandering males.

5. Accidental Entry

Some spiders enter homes accidentally — carried in on firewood, potted plants, boxes from storage units, or produce from the garden. Banana spiders occasionally arrive in fruit shipments, and Joro spiders may establish themselves in new areas through hitchhiking.

Solution: Inspect items before bringing them inside. Shake out firewood outdoors. Check potted plants for webs and egg sacs.

6. They Were Born There

Many house spiders never came from outside — they hatched from egg sacs indoors and have lived their entire lives inside your home. These species have adapted to indoor conditions and may not survive outdoors.

Solution: Remove egg sacs when found. Reduce the breeding population with sticky traps, regular cleaning, and prey insect control.

How Spiders Get In

Common entry points include:

• Gaps under doors (especially garage doors)
• Cracks in foundations
• Gaps around windows and window screens
• Openings around utility lines, pipes, and wires
• Vents without screens
• Through open doors and windows

The Most Effective Prevention

Combine these strategies for maximum effect:

1. Seal all entry points with caulk, weatherstripping, and door sweeps.
2. Reduce indoor prey insects.
3. Eliminate clutter and hiding spots.
4. Apply natural repellents or spider spray around entry points.
5. Monitor with sticky traps.

For detailed prevention strategies, see spider prevention tips and how to get rid of spiders. For comprehensive information, visit our complete guide to spiders.

Expert Insights

Understanding why spiders enter homes has been central to my 15-year IPM career. The answer is simple: they are following food and shelter. I always tell clients that if you have a spider problem, you likely also have a prey insect problem. One client in Indiana had persistent spider issues that no amount of spraying resolved. A thorough inspection revealed a significant cricket population in the crawl space, which was the primary food source attracting spiders. Once we addressed the crickets, the spider numbers dropped dramatically. — Sarah Mitchell, BCE

Sources and References

• National Pest Management Association (NPMA)
• University of California Riverside Spider Research
• Ohio State University Extension
• Burke Museum of Natural History and Culture

Main Causes

Indoor spiders activity reflects two drivers — a hospitable indoor environment and a sufficient supply of insect prey. Spiders enter through gaps under doors, around windows, utility penetrations, and any opening leading to attics, basements, garages, or crawl spaces. Once inside they settle wherever undisturbed corners, low light, and easy prey access converge. Cooler weather pushes outdoor species inside in late summer and fall as they seek mating sites or shelter. The most important upstream driver is the indoor insect population — homes with active fly, gnat, moth, or other pest activity sustain larger spider populations than homes without prey. Cluttered storage areas, accumulated webbing, and outdoor lighting that draws nocturnal insects all amplify the indoor pressure.

How to Identify

Identification matters because risk and control differ significantly by species. Most household spiders — cellar spiders, common house spiders, jumping spiders, wolf spiders — are harmless and beneficial. Two species in North America warrant caution: the black widow with its shiny black abdomen and red hourglass marking, and the brown recluse with its violin-shaped marking and uniform tan-brown coloring without leg banding. Check webs for shape and structure: tangled cobwebs in corners indicate cellar or common house spiders; funnel-shaped webs near ground level indicate funnel-web species; sheet webs across grass are usually grass spiders. Single sightings without webs are usually transient outdoor species and do not indicate an infestation.

Risk and Severity

Most spiders found in and around North American homes pose no medical risk to humans and provide net benefit by reducing other pest populations. Two species warrant medical caution: the black widow, whose venom can produce systemic symptoms including muscle cramping, abdominal pain, and elevated blood pressure; and the brown recluse, whose bite can produce a slowly developing necrotic lesion in a minority of cases. Bites from either species generally respond well to medical care, and fatalities are extremely rare. The far more common spider-related problem is aesthetic — webs, egg sacs, and visible spiders cause distress without medical significance. Risk concentrates in undisturbed storage areas, garages, basements, and outbuildings.

Solutions and Actions

For most spider species the goal is removing webs and reducing prey rather than chemical treatment. Vacuum or sweep down all visible webs weekly, including egg sacs, in garages, basements, attics, eaves, and exterior corners. Reduce indoor insect populations by maintaining screens, sealing entry points, and addressing any active pest issue — fewer insects means fewer spiders. Apply a residual insecticide barrier to the foundation perimeter, around windows and doors, and in eaves to deter newly arriving spiders. For confirmed black widow or brown recluse populations in storage areas, use professional pest control, wear long sleeves and gloves when handling stored items, and shake out shoes and clothing left in garages or basements. Single sightings indoors without webs are usually transient and need no chemical response.

Prevention

Prevention works by reducing indoor prey and limiting entry. Vacuum corners, ceiling angles, undisturbed storage, and basement and garage areas weekly to remove webs, egg sacs, and the dust that supports prey populations. Seal gaps around doors, windows, utility penetrations, and foundation cracks. Address active insect pests promptly because indoor spider populations track prey availability. Switch exterior lights to yellow or warm LED bulbs that attract fewer flying insects, and position outdoor lighting away from doors and windows. Inspect and shake out shoes, gloves, and clothing left in garages, basements, sheds, and storage areas. Trim shrubs and ground cover away from the foundation, and keep firewood and debris stacks at least twenty feet from the structure.

Frequently Asked Questions

Why do spiders come inside my house?

Spiders enter homes seeking food (prey insects), shelter from weather, moisture, and suitable environments for reproducing. Many species follow their prey inside — if your home has flies, ants, crickets, or other insects, spiders will follow. Some species, like house spiders, have adapted to living exclusively indoors.

Do spiders come inside more at certain times of year?

Spider sightings inside homes tend to increase in late summer and fall. This is partly because male spiders become more active while searching for mates, and partly because cooling temperatures drive outdoor species to seek warmer shelter. However, many indoor spiders are active year-round.

How do spiders get into my house?

Spiders enter through any small gap or opening — cracks in foundations, gaps under doors, damaged window screens, openings around utility pipes and wires, and through ventilation systems. They can flatten their bodies to fit through surprisingly small spaces. Sealing these entry points is the most effective way to keep them out.

Will turning off outdoor lights keep spiders away?

Reducing or repositioning outdoor lights near entry points can help. Lights attract prey insects, and spiders follow the food. Switching to yellow or sodium vapor bulbs, which attract fewer insects, and positioning lights away from doors and windows can reduce the number of spiders drawn to your home's perimeter.