After having found 7 mice (4 killed by cats, 3 alive and scurrying) in the house in one day last week, I broke down and called Terminix. Eric, the service guy, went over with me where I was noticing the mice, scanned a bit in the rafters of my basement and behind appliances in my kitchen and then explained to me their service program. Where, year-round, they would come and make sure things like mice and giant spiders were not crawling into my house. (I know Quigs will be very happy to hear this.)
Then, I don't have to worry about looking for holes. It's their job. Win/Win. So, today, Mousehunter Jim came to my house. He spent from 10:15 a.m. until 12:45 p.m. doing nothing but sorting out where the mice were getting into the house. Apparently there are pre-fabbed boards that have holes in them to run pipes and wires through that then the builders cover up with insulation, which mice say "Weeeee warmth!" about before they chew through it, cuddle into it, have a zillion babies and then when they shred that insulation apart, they crawl through the unfinished parts of the basement to make new nests. So, he pulled out the shredded insulation filled with feces and filled in the holes with wire mesh and caulk that the mice won't chew through in fear of cutting up their sweet little brown rodent faces. He found a lot of those holes. Hooray, new construction.
Then he went through the basement areas looking for holes that showed "daylight" in the house. He'd identify a spot and thump on the floor until I could move whatever was in the way to identify where that space was coming through. Things like the gas pipe going up to the laundry room behind the litterboxes where a mouse could crawl up, should he be living in the basement, or the water hoses going up from the basement to the refrigerator, etc. Jim was very thorough. Then he went out and sealed up any holes leading into the garage, and he set some covered bait traps out there.
It was clear that Mousehunter Jim was very serious about his work. He was also very good at educating me on things to look for in the house. He'll be back when the snow melts a bit to do a more thorough job looking for weak spots on the outside of the house, but we should be pretty good for the winter. Better than that, if I have any problems, I have a direct phone line straight to Mousehunter Jim. He'll come to the house and take care of whatever I need him, too.
If Jim is the Mouse God. I'm like the Pope of Mouse killing with my direct line.