Common pests in Illinois homes

House Mouse

The most common rodent in homes year-round. Small, fast, and capable of squeezing through a gap the width of a pencil, house mice nest inside walls and breed quickly.

Norway Rat

The large, burrowing rat found near foundations, dumpsters, and sewer lines. Norway rats cause serious structural damage and carry diseases that pose real health risks.

Cockroaches

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American Cockroach

The largest common house cockroach, reddish brown and nearly two inches long, mostly found in basements, drains, and commercial buildings.

German Cockroach

The small light-brown roach behind most kitchen infestations. It breeds fast, hides in tight warm spots, and rarely clears up on its own.

Ants

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Carpenter Ant

A large black ant that excavates wood to nest. It does not eat the wood, but a long-established colony can cause real structural damage.

Pavement Ant

A small dark ant that nests under sidewalks and slabs, trails indoors for food, and throws up fine soil at crack edges along driveways and foundations.

Termites

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Subterranean Termite

The most destructive wood-destroying insect in North America. It lives underground and attacks wood from below, invisibly, for years before homeowners notice.

Bed Bugs

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Bed Bug

A flat, reddish-brown insect that feeds on blood while you sleep. It does not carry disease, but an infestation grows quickly and almost always requires professional treatment.

Stinging Insects

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Cicada Killer Wasp

A very large, solitary wasp that digs burrows in bare ground and hunts cicadas for its larvae, alarming to look at but not aggressive toward people.

Yellowjackets, Wasps & Hornets

Social wasps that build paper nests and defend them aggressively, posing a genuine sting risk in summer and fall when colonies reach full size.

Mosquitoes

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Mosquito

Blood-feeding flies that breed in standing water. Several species in the Upper Midwest and Mid-Atlantic carry West Nile virus, and one imported species bites aggressively during the day.

Spiders

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Black Widow Spider

A shiny black spider with a distinctive red marking on the abdomen, whose venom is medically significant but rarely causes serious harm in healthy adults.

Brown Recluse Spider

A shy, tan spider with a fiddle-shaped marking and six eyes, found mainly in southern and central Illinois, whose bite can occasionally cause serious skin damage.

Common House Spider

The small, tan-to-brown spider responsible for most cobwebs in homes and garages, harmless to people, and effectively controlled through web removal and basic exclusion.

Wolf Spider

A large, fast-moving ground spider that hunts without a web and is harmless to people, often alarming homeowners by its size and speed alone.

Flies

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Cluster Fly

Large sluggish flies that spend the winter clustered in attics and wall voids, emerging on warm days to gather at windows in large numbers.

Drain Fly

Small fuzzy flies that breed in the organic sludge inside drains and rarely go away until that sludge is physically removed.

Fruit Fly

Tiny tan flies drawn to overripe fruit and fermenting liquids, capable of going from egg to adult in about a week under warm conditions.

Ticks

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American Dog Tick

A large brown-and-white tick found in grassy and brushy areas. It is the primary vector of Rocky Mountain spotted fever in the eastern United States.

Deer Tick

A small dark tick that carries Lyme disease. The nymph stage is the size of a poppy seed and accounts for most human infections in the Upper Midwest and Mid-Atlantic.

Occasional Invaders

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Box Elder Bug

A flat black bug with orange-red markings that piles onto sun-warmed walls in fall, then shows up inside all winter. Harmless but a real nuisance.

Brown Marmorated Stink Bug

An invasive shield-shaped bug that enters homes by the hundreds each fall and releases a foul odor when disturbed. Harmless to people, serious to crops.

Camel Cricket

A large humpbacked cricket with no wings and very long legs that thrives in damp basements and crawl spaces. Startling but harmless.

Multicolored Asian Lady Beetle

The ladybug-looking beetle that invades homes by the hundreds each fall. It bites lightly, stains surfaces, and smells bad when disturbed.

Wood-Boring Insects

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