Fighting the friendly flies

For the last week I’ve been fighting this invasion of houseflies. I strongly suspect that one fly got in, laid eggs, and they hatched; the doors simply haven’t been open long enough to let in so many. By now I’m down to one or two, but they’re the active type of fly, that won’t light anywhere long enough to let you swat ’em, and they insist on circling in front of you, or just at the corner of your vision, and being as distracting as possible. I suppose I could turn the A/C down to 68 or thereabout, and make them sluggish enough they’d light and stick, but if I did everyone else in the house would complain bitterly of the cold (normally we keep the house at 78 or 79).