I saw some kind of bug crawling inside a bathroom ceiling light fixture, so I assume it crawled in through the attic to the ceiling to the light fixture and then into the rest of the house.
I decided to look all around and I also noticed light leaking through the corners of the exit doors despite weatherstripping.
They may also be coming in under sliding glass doors, cable and telephone jacks, light switches, electric outlets, through gaps around plumbing and gas lines, from under baseboards and so on.
I call a pest service periodically, but pesticide spraying will never end if the living space is full of pathways to the outside.
I think all of these openings can be sealed tight with various sealants and caulks.
I can't think of a way to seal the built-in glass door in front of the natural gas fireplace that will be safe and handle the heat.
Has anyone successfully sealed out insects with pest proofing methods?