Boxelder Bug: These black and red bugs are often found on the sunny sides of homes and buildings as the weather cools. In October, they gather in large numbers, looking for warm places to spend the winter. They are attracted to the warmth of buildings and can slip inside through small cracks. While they don’t bite or damage property, their presence can be a nuisance, and they may stain surfaces if crushed.

Cluster Fly: Cluster flies are larger, slower-moving flies that look similar to houseflies. In October, they seek shelter in attics and wall voids to hibernate through the winter. They enter homes in large groups, often clustering near windows or in upper rooms. Their slow movement and tendency to gather in groups make them noticeable, and they can become active on warm winter days, causing annoyance indoors.

Brown Marmorated Stink Bug: These shield-shaped bugs are brown with white markings and release a strong odor when disturbed. In October, they look for protected places to overwinter, often entering homes through gaps around windows, doors, and siding. Their numbers increase as temperatures drop, and they can be found crawling on walls or windows. While they don’t cause structural damage, their smell and presence can be unpleasant.

Black Rat: Also known as roof rats, these rodents are agile climbers and often enter homes in the fall to find food and warmth. In October, as outdoor food sources dwindle, they look for shelter in attics, garages, and wall voids. They can chew through wires, insulation, and stored items, causing property damage and posing health risks through droppings and urine. Their presence is often detected by scratching noises or droppings.

Western Conifer Seed Bug: This bug is brown with long hind legs and emits a pine-like odor when disturbed. In October, it seeks out warm places to overwinter, often entering homes through small openings. They are attracted to the warmth of buildings and can be seen on exterior walls or inside windows. While harmless to people and property, their sudden appearance indoors can be alarming.

Yellowjacket Wasp: Yellowjackets are aggressive wasps with black and yellow markings. In October, their colonies reach peak size, and food becomes scarce, making them more likely to enter homes or hover around outdoor gatherings. They are attracted to sweet foods and drinks, and their stings can be painful or cause allergic reactions. As temperatures drop, they may seek shelter in wall voids or attics.

House Mouse: House mice are small, gray rodents that become more active indoors in October as they search for warmth and food. They can squeeze through tiny openings and quickly establish nests in walls, basements, or storage areas. Mice contaminate food, chew on wires and insulation, and leave droppings that can spread disease. Their activity often increases in the fall as outdoor conditions become less favorable.