Insects and wildlife exhibit a variety of behaviors or adaptations that help them to survive the harsh conditions of winter. These “overwintering pests” can be quite frustrating to homeowners as they begin taking refuge indoors. While trees and rocky hillsides provide overwintering sites in nature, man-made structures that now dominate the landscape are perfectly acceptable to these organisms.
Common Fall Pests
In the fall, brown marmorated stink bugs gather to find protective winter habitat and find their way into wall voids around windows, doors, outlets, light fixtures, and air conditioners.
Boxelder bugs are one of the many pests that come in on a potted plant, or through a crack, an open door, a hole in a screen, or a piece of firewood.
Cluster flies do not feed or reproduce indoors, but cluster in protected areas, especially attics.
Multicolored Asian ladybeetles gather in large groups in the fall, and tend to invade buildings for overwintering where they find gaps and holes in structure, around eaves, windows and foundations.
Ticks are still active in fall. Adult ticks are out looking for a fall feast in preparation for winter. Because they've fed a number of times at this point in their life cycle they are more likely to be carrying diseases.
Western conifer-seed bugs (WCSB) are overwintering pests that live outside during the summer and feed on pinecones. In the fall, they enter structures for protection against the cold and desiccating wind.
Beginning in the spring and into the fall, both little brown bats and big brown bats have “maternal roosts” consisting of females and the young-of-the-year congregating in the warm upper sections of buildings.
Peromyscus mice spend most of their lives outdoors foraging on natural food sources, but in the fall, they will enter buildings to find a suitable place to nest, and protect themselves against cold temperatures.
Snakes inside buildings are usually the result of seeking locations for winter hibernation or pursuing prey, such as mice. But they can’t get in unless there’s a hole for them to enter through.