I often get asked about the most common ways that bugs get into homes. My answer to this question is that they are either brought in, or they come in through numerous openings and voids, often being doors and windows.
During the course of us coming and going, bugs use these opportunities to sneak in behind us. Other times, doors and windows are simply left open, allowing pests of all kinds to enter.
Doors and windows are obviously designed to open and close. Over a period of time, the seals around doors and windows can break, tear, or simply become old and compressed, allowing insects easy access to our homes. Weather stripping around these types of areas should be checked periodically and replaced as needed.