Spiders Eat Other Pests: The Pest Control Benefit of Spiders

Spiders are generalist predators that consume virtually any insect or arthropod they can overpower. This makes them one of the most effective natural pest control agents available — and they work for free. Here is a look at the pests spiders keep in check.

Pests That Spiders Eat

Flies

House flies, fruit flies, drain flies, and gnats are staple prey for web-building spiders like house spiders, cellar spiders, and orb weavers. In terms of sheer numbers, flies are probably the most common spider prey in homes.

Mosquitoes

Spiders eat mosquitoes regularly, particularly web-building species that trap mosquitoes flying in low-light conditions. This provides a direct health benefit by reducing disease-carrying insects.

Cockroaches

Some larger spiders, including wolf spiders and house spiders, prey on cockroach nymphs (juveniles). While spiders alone cannot control a cockroach infestation, they contribute to keeping populations in check.

Moths

Both web-building and hunting spiders catch moths. This includes clothing moths that damage fabrics and pantry moths that infest stored food.

Silverfish

Ground-dwelling spiders and hunting spiders readily catch silverfish, which share the same dark, damp habitats.

Earwigs

Wolf spiders and other ground hunters prey on earwigs.

Ants

Some spider species prey on ants, though most spiders avoid ant-heavy areas due to the risk of being overwhelmed.

Bed Bugs

While not a primary predator of bed bugs, some spiders (particularly house spiders and cellar spiders) will catch and eat bed bugs that blunder into their webs.

Other Spiders

Many spider species are cannibalistic and will eat other spiders. Cellar spiders are particularly notable for killing and eating black widows and other spiders that enter their territory.

Agricultural Pests

In gardens and agricultural settings, garden spiders, crab spiders, and orb weavers consume crop-damaging insects including aphids, leafhoppers, beetles, and caterpillar moths.

Quantifying the Benefit

Research has estimated that:

• Global spider populations consume 400 to 800 million metric tons of insects annually.
• In agricultural systems, spiders provide pest control valued at billions of dollars per year.
• A single spider can consume several thousand insects over its lifetime.
• In homes, a few resident spiders can consume hundreds of pest insects per year.

Encouraging Beneficial Spider Activity

If you want to maximize spiders' pest control benefits:

• Tolerate harmless spiders (which is most of them) in areas where they do not bother you.
• Avoid broad-spectrum pesticide applications that kill spiders.
• Leave garden spiders and orb weavers alone outdoors.
• Plant diverse vegetation to support spider habitat in your yard.
• Use targeted pest control methods that spare spiders when possible.

The Balanced Perspective

Spiders are not a replacement for pest control — a spider in your kitchen will not solve a cockroach infestation. But they are a valuable supplemental force that reduces the overall pest pressure in and around your home.

The key is coexistence with boundaries: tolerate harmless spiders where you can, remove them from living spaces when needed, and reserve aggressive control for venomous species and genuine infestations.

Spider Specialization

While most spiders are generalist predators, some species show interesting dietary preferences:

• Cellar spiders are notable for preying on other spiders, including dangerous species like black widows. If you have cellar spiders in your basement, they may actually be protecting you from more dangerous species.
• Jumping spiders are visual hunters that preferentially target moving prey. They are particularly effective against flies and other active insects.
• Wolf spiders are ground-level hunters that specialize in crawling insects like crickets, cockroaches, and ground beetles.
• Orb weavers and garden spiders catch primarily flying insects. The size and placement of their webs determines what prey they intercept.

When Spiders Cannot Solve Your Pest Problem

Despite their value, spiders cannot control every pest situation:

• Large infestations: A spider population cannot keep pace with a rapidly reproducing pest population like cockroaches or fruit flies. Address the root cause of the infestation directly.
• Hidden pests: Termites, bed bugs, and other pests that live inside walls, mattresses, or wood are largely inaccessible to spiders.
• Outdoor pests: Yard-level pests like ticks, grubs, and lawn-damaging insects are not effectively controlled by most spider species.

In these cases, targeted pest control is necessary. But allowing spiders to remain as a supplemental control force reduces the overall pest pressure in your home.

For more on spider management, see how to get rid of spiders and our complete guide to spiders.

Expert Insights

One of the most important concepts I teach in my IPM consultations is that spiders are pest control allies. In 15 years of practice, I have documented spiders consuming cockroaches, ants, flies, mosquitoes, moths, beetles, and even other spiders. On one commercial account, a warehouse with a healthy spider population had significantly fewer stored product pest issues than comparable facilities that used aggressive spider elimination programs. — Sarah Mitchell, BCE

Sources and References

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

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

What pests do spiders eat?

Spiders consume a wide variety of pest insects, including mosquitoes, flies, cockroaches, ants, moths, beetles, earwigs, and crickets. Some larger spiders can even catch and eat small rodents or lizards, though this is rare. Globally, spiders consume an estimated 400 to 800 million metric tons of insects annually.

Are spiders better than pesticides for pest control?

Spiders alone are not a replacement for targeted pest control, but they do provide significant supplemental control. They are particularly effective against flying insects caught in webs and ground-dwelling pests caught by hunting spiders. Unlike pesticides, spiders provide continuous, free pest control with no chemical residues.

Should I keep spiders around to control other pests?

In many cases, yes. If the spiders in your home or garden are harmless species — which the vast majority are — they are providing free, continuous pest control. Tolerating harmless spiders can reduce your reliance on chemical pest control and help maintain a balanced ecosystem around your home.

What should I recheck first for pest-eating spiders?

Recheck the exact place, timing, and repeated signs connected with pest-eating spiders before changing your plan. A single sighting or old web can mean something very different from fresh activity in several rooms. Confirm whether insects, clutter, moisture, gaps, or stored items are supporting the issue, then match the response to what you actually found.