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Identifying Common Household Insects in Pennsylvania

“What is that crawling across the kitchen floor? Why are there holes in my new cashmere sweater? Why is the oatmeal full of webs?”

If you’ve asked questions like these, then you need this fact sheet. Proper pest identification is the first step in making an integrated pest management (IPM) decision. Improper identification can lead to unsuitable solutions to pest problems. The pictures and descriptions in this publication should help the homeowner or apartment dweller identify common insects found in the home. Once the pests have been identified, other sources of information can be used to determine the species’ potential as a pest and how to prevent or control them. Good places to obtain this information are the Penn State Extension website, Penn State Department of Entomology website or your local Penn State Extension office.

The phone number may be found in the Blue Pages of the phone book.

Indian Meal Moth (adult)

Commonly found: pantry and kitchen

A common flour, pasta, and cereal pest, this small insect will likely go unnoticed until it becomes abundant. The beetle is about 1⁄16 inch long.

Saw-Toothed Grain Beetle (adult)

Commonly found: pantry and kitchen

A common flour, pasta, and cereal pest, this small insect will likely go unnoticed until it becomes abundant. The beetle is about 1⁄16 inch long.

Larder Beetle (adult)

Commonly found: pantry and kitchen

This household pest lays its eggs in and feeds on dry pet food, corn meal, animal products, and dead insects. The beetle is dark brown and approximately 1⁄2 inch in length.

American Cockroach (adults, nymphs, and egg capsule)

Commonly found: pantry, kitchen, bathroom

This reddish-brown cockroach is approximately 1 1⁄2 inches in length. It is commonly found in basements, packing houses, and grocery stores and feeds on a variety of materials. It likes wet areas.

German Cockroach (adults nymphs, and egg capsules)

Commonly found: pantry and other areas

The German cockroach is the most common cockroach species in houses, apartments, and hotels. Usually found in kitchen and bathrooms, it is 1⁄2 to 5⁄8 inch long and tan to light brown. Look for the dark stripes on its “neck.”

Brown-Banded Cockroach (adult)

Commonly found: pantry and other areas

This pest can be found in warmer areas of homes and apartments and is about 1⁄2 inch in length and light brown. It can rapidly spread throughout an entire building.

Oriental Cockroach (adult)

Commonly found: kitchen, basement, and other areas

Oriental cockroaches prefer dark, damp areas, such as beneath sinks and washing machines and in basements. They are about 1 1⁄4 inches long, dark brown, and found with decaying organic matter indoors and out.

Black Carpet Beetle (adult)

Commonly found: throughout house

The black carpet beetle is 1⁄4 to 1⁄2 inch long and can be found in lint around baseboards and other areas. The larvae eat almost any animal product, including leather, wool, silk, feathers, and hair.

Bed Bug (adult)

Commonly found: bedroom

Bed bugs can be found hiding in cracks and crevices in walls and floors, as well as in furniture and beds in bedrooms. They are oval, chestnut-brown insects that are flattened from top to bottom, measuring less than 1⁄4 inch long.

Human Louse (adult, nymph, and egg attached to hair shaft)

Commonly found: people and clothing

Head and body lice are very small, measuring 1⁄16 to 1⁄12 inch. Sharing hairbrushes, combs, hats, clothes, toilet seats, and bedding can spread these blood-sucking insects.

Tick (engorged adult)

Commonly found: forests, meadows, fields

Ticks feed on the blood of vertebrate animals and can transmit diseases, such as Lyme disease. Ticks are very small, from 1⁄50 to 1⁄8 inch long, and can be found in long grasses and shrubs.

Flea (adult)

Commonly found: pets, carpeting, animal bedding, lawns

Fleas are small insects less than 1⁄4 inch long and are dark brown (photo lightened to show detail). Fleas are usually found on cats and dogs, but some types will attack other animals and humans.

Mosquito (engorged adult)

Commonly found: inside and outside of homes

Mosquitoes are small flies that breed in standing water. Females must have a blood meal before laying eggs, which brings them into households and yards.

House Fly (adult)

Commonly found: in and outside of homes

House flies can transmit diseases to humans and can be identified by four dark stripes on their thorax. The larvae (maggots) feed on decaying matter and are about 1⁄2 inch long.

Paper Wasp (adult)

Commonly found: under soffets and eaves

Paper wasps can be found nesting around homes or other structures. Adults are about 3⁄4 to 1 inch long, slender, and reddish orange to dark brown or black in color.

Asian Lady Beetle (adults)

Commonly found: nuisance pest

Lady beetles can be found in homes, seeking warmth during the months from September to April. These harmless insects are broadly oval, yellow to red, and may have black spots.

Booklice (adult)

Commonly found: throughout house

Booklice resemble lice in size and shape but only feed on fungi, molds, or materials that support mold growth, as well as the starchy paste of wallpaper and books.

Western Conifer Seed Bug (adult)

Commonly found: nuisance pest

This insect becomes a nuisance when it enters homes in search of overwintering sites in the fall. Adults are 3⁄4 inch long and brownish on top.

Vinegar Fly (adult)

Commonly found: pantry and kitchen

Vinegar flies–sometimes mistakenly called fruit flies–are usually found around overripened fruit and vegetables. Adults are tiny, measuring 1⁄16 to 1⁄12 of an inch long, and are light yellowish brown to dark brown in color.

European Earwig (adult)

Commonly found: nuisance pest

Earwigs are 5⁄8-inch long and dark reddish brown. They become a pest when they seek shelter in homes.

House Centipede (adult)

Commonly found: nuisance pest

House centipedes are long and flat and have fifteen pairs of legs with the last pair (on adult females) nearly twice the length of the body. These harmless pests are about 1 1⁄2 inches in length.

Silverfish (adult)

Commonly found: nuisance pest

Silverfish are either gray or silver with long antennae and three long filaments extending from the abdomen. They feed on any substance containing starch, including books, linens, and cereals.

Brown Marmorated Stink Bugs (adult)

Commonly found: nuisance and garden pest

Stink bugs are so named because their natural defense is releasing smell that “stinks.” Stink bugs have a wide, shield-shaped body, and measure about 1⁄2 inch long.

Carpenter Ant (worker)

Commonly found: structural wood

Large, dark-colored carpenter ant workers often invade homes in search of food and may excavate moist, rotting wood and other soft materials to make satellite nests. The workers are wingless and 1⁄4 to 1⁄2 inch in length.

Termite (workers and soldiers)

Commonly found: structural wood

Termites are social insects that live in colonies and excavate wood. While an ant has a narrow, wasp-like waist, a termite has a broad waist. Workers are creamy white, wingless, and 1⁄8 to 1⁄4 inch in length.

Carpenter Bee (adult)

Commonly found: structural wood

Carpenter bees resemble bumble bees in both size and appearance but have shiny, black, hairless abdomens. They are 1⁄2 to 1 inch long and can be found nesting in soft wood, usually under the eaves in homes. Males have no stinger; females do not sting unless provoked.

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