What pest is it, and where does it live?

A house mouse is a small rodent with a pointed snout, large ears and droppings about the size of a grain of rice. In Greater Toronto Area homes they nest in wall voids, attics and behind appliances. They chew food packaging, insulation and wiring, and they fit through a gap about the width of a pencil.

Rats around Greater Toronto Area homes are larger than mice, with droppings about 1 to 2 cm long and burrows along foundations, decks and sheds. They chew wood, plastic and wiring to reach food and shelter. Activity is often outdoors first, then in garages, basements and wall voids.

Bed bugs are flat, apple-seed-sized insects that feed on blood at night. In Greater Toronto Area homes and apartments they hide in mattress seams, bed frames, headboards and sofa creases, and they travel in luggage and used furniture. They do not damage the building. They leave bites, spots of blood and dark droppings on sheets.

German cockroaches are small, light-brown insects with two dark stripes behind the head. In Greater Toronto Area homes and condos they live in warm, humid kitchens: behind fridges, under sinks and inside appliance motors. They spoil food, leave a musty smell, and move between units through shared walls.

Pavement ants are the small brown or black ants that march indoors each spring across the Greater Toronto Area. The colony lives in soil under patios, driveways and foundation cracks. They are a nuisance in kitchens. They do not excavate house framing the way carpenter ants do.

Carpenter ants are large, often black ants that excavate damp or damaged wood to nest. They do not eat the wood. In Greater Toronto Area homes they nest in decks, window frames, rooflines and wall voids, especially where wood stays wet. Fine sawdust below the nest is the usual clue. Homes near ravines see them often.

Wasps and hornets build paper nests that grow fastest in late summer, when the colony is largest. On Greater Toronto Area houses the usual spots are under eaves, behind soffits, in sheds and inside wall voids. A nest by a door or play area is a sting risk. A nest inside a wall can chew through drywall.

Fleas are tiny jumping insects that ride indoors on pets. In Greater Toronto Area homes the adults bite people around the ankles, while eggs and pupae sit in carpets, pet bedding and sofa creases. They do not damage the building. The bites continue for weeks if the eggs in the carpet keep hatching.

Mosquitoes around Greater Toronto Area homes breed in standing water and rest in shade during the day. A saucer under a pot, a clogged eavestrough or a low spot in the lawn is enough. They do not nest in the house. Biting is worst at dusk, in sheltered gardens and near ravines.

House spiders in the Greater Toronto Area build webs in quiet corners: basements, window wells, garages and ceiling edges. They do not damage wood or wiring. A sudden number of spiders usually means the basement has the insects they eat, often alongside damp conditions that also suit silverfish and centipedes.

Silverfish are fast, silvery, carrot-shaped insects that need damp rooms. In Greater Toronto Area homes they live in bathrooms, basements and laundry areas. They feed on paper, wallpaper paste, cardboard and stored fabrics. Large numbers point to humidity, not a dry, well-ventilated room.