Field guide · Plate index

Identify the pest: the Field Key

Five plain questions — where you found it, its size, its wings, the season, and the sign that came with it — narrow Northwest Pennsylvania's common house pests to a short list. Every candidate links to a full plate: identification marks, look-alikes, hiding places, risk, what works, what does not, and when to call a licensed professional.

Scope, declared: the key identifies insects and other small pests. Wildlife — bats, raccoons, squirrels — is a different trade under different Pennsylvania rules; it has its own page: Wildlife in Northwest Pennsylvania houses, including the bat-in-the-house protocol. The grape belt’s watch pest has a plate too: spotted lanternfly.

The complete table — every pest on the desk

28 plates, in the order the desk reaches for them
Pest	The short of it	Season
Brown marmorated stink bug Halyomorpha halys	Shield-shaped, mottled brown, with pale bands on the antennae. The classic October invader of warm, south-facing Erie walls.	fall, winter
Cluster fly Pollenia spp.	Slow, dull-grey flies that crowd attic windows in autumn and blunder out on mild winter days.	fall, winter
Multicolored Asian lady beetle Harmonia axyridis	Orange-to-red dome beetles with highly variable spots — and a black M-shaped mark behind the head. They bite gently and stain.	fall, winter, spring
Boxelder bug Boisea trivittata	Black-and-red flat bugs that mass on sunny walls near boxelder and maple trees each autumn.	fall, spring
House mouse Mus musculus	The year-round tenant of Erie walls: small, grey-brown, and inside at the first hard frost — if it ever left.	fall, winter, year-round
Norway rat Rattus norvegicus	Heavy, blunt-nosed burrowing rat of basements, sewers, and lakefront alleys. Unmistakable by size alone.	fall, winter, year-round
German cockroach Blattella germanica	Small, tan, and the hardest kitchen pest in rental housing. If it has two dark stripes behind the head, it is this one.	year-round
American cockroach Periplaneta americana	The big red-brown roach of basements, drains, and boiler rooms. Impressive, fast, and usually a plumbing problem first.	summer, year-round
Bed bug Cimex lectularius	Flat, apple-seed-sized, and year-round in rental stock, hotels, and second-hand furniture. Identification is by the bug or its traces — never by bites alone.	year-round
Carpenter ant Camponotus spp.	Large black ants that excavate damp wood. Spring swarmers and piles of coarse sawdust are the tell.	spring, summer
Odorous house ant Tapinoma sessile	Tiny dark ants that trail to any sweetness in the kitchen — and smell of rotten coconut when crushed.	spring, summer
Yellowjacket Vespula spp.	Glossy yellow-and-black wasps that nest in walls and lawns and turn defensive by August. The late-summer picnic pest is the same insect.	summer, fall
Paper wasp Polistes spp.	Long-legged, mahogany wasps under the eaves, building small open umbrella nests. The calmest wasp you will meet — if you leave the nest alone.	spring, summer
Bald-faced hornet Dolichovespula maculata	Black-and-ivory, football-nest builder in trees and on gable ends. Not a true hornet — a large aerial yellowjacket with a short temper at home.	summer, fall
Eastern subterranean termite Reticulitermes flavipes	The quiet structural pest of Pennsylvania: lives in soil, feeds in wood, and shows itself in spring swarms and mud tubes.	spring
House centipede Scutigera coleoptrata	Thirty long legs, a blur across the basement wall, and entirely on your side: it hunts the insects you actually have a problem with.	year-round, summer
Silverfish Lepisma saccharina	Silvery, tapering, wingless — a damp-paper pest older than the dinosaurs, at home in Erie basements and bathrooms.	year-round
Indianmeal moth Plodia interpunctella	The pantry moth: small, two-toned, fluttering at the kitchen light while its larvae web through flour, cereal, and bird seed.	year-round, summer
Clothes moth — webbing & case-bearing Tineola / Tinea spp.	Small, pale, light-shy moths whose larvae eat wool, fur, and feather. Closets and stored winter clothes are the habitat — and Erie winters mean a lot of stored wool.	year-round
Blacklegged (deer) tick Ixodes scapularis	Pinhead nymphs in late spring, sesame-seed adults in autumn — and the tick that carries Lyme disease in Erie County.	spring, fall, summer
Cat flea Ctenocephalides felis	The flea on nearly every dog and cat in Pennsylvania, despite the name. A summer problem that starts on the pet and lives in the carpet.	summer, fall
Common spiders of NW PA houses Parasteatoda, Pholcus, Steatoda & others	Cobweb spiders in the corners, cellar spiders on the basement ceiling, and the occasional bold jumping spider on the sill. Mostly free pest control.	year-round
Mosquito Culex spp.	Culex mosquitoes of dusk and standing water — a biting nuisance, and the insect Erie County tests for West Nile virus each summer.	summer
Carpenter bee Xylocopa virginica	A big spring bee with a bare, shiny abdomen, boring neat round holes in decks and fascia — and forever mistaken for a bumblebee.	spring, summer
Drain flies & small flies Psychodidae & allies	Moth flies at the sink, fruit flies at the bananas, gnats in the houseplants: the breeding site is the whole answer.	year-round, summer
Spotted lanternfly Lycorma delicatula	Not established in Erie County as of 2025 surveys — the grape belt’s watch pest. Grey spotted wings, a flash of red, and a duty to report it.	summer, fall
Stored-product beetles Stegobium, Lasioderma, Tribolium spp.	Beetles inside the flour and the spice jars: find the infested package and the problem mostly ends there.	year-round
Carpet beetle Anthrenus & Dermestes spp.	The commoner cause of ‘clothes moth’ damage: mottled little beetles, and hairy larvae that eat wool — and dead cluster flies.	spring, year-round

Two cautions the desk repeats everywhere: bites alone never identify a pest — find the insect or its traces — and a specimen kept in a jar with a coin for scale is worth a dozen photographs taken across a room.