A long time ago, we had some in our pantry. I tracked them down to a bag of unshelled pecans that had been there a few years, completely forgotten.

Was there webbing or moths in the bag? I can't find any obvious signs that they've infested a food source.

Any bird seed around? Kibble or other dry pet food?

And slightly related to bird seed, sometimes rodents nest in attics and stash food so I suppose it's possible that the moths are coming from a food source in the attic--might as well caulk that gap.

I have one bag of dried cat food, but I opened the bag and I'm not seeing any moths or worms. I did tape up the hole one day for a few hours when the furnace/air conditioning wasn't running and I didn't see any moths stuck to the tape. I'm afraid to tape it up permanently in case it's vented that way for a reason.

I didn't see webbing. It was so long ago, but I found either dead moths or larvae or something, so I just knew, And after I cleaned it all up, the problem never resurfaced.

Try putting some pheromone traps in laundry and pantry. Also move all flours, cereals, etc. into sealed glass or plastic containers. Wash down all pantry surfaces.

Or, deploy the traps outside.

@zumba1 Thank you so much for your response! I finally figured out that the traps were the problem! I originally bought them for fungus gnats around my plants and I guess, over time, as I bought more traps, I started attracting moths. And they found an easy way into my house through the vent in my laundry room! Just like you, I started noticing them on my window screens. But again, just like you, I was scared if I threw away the traps, that the moths would keep coming and lay eggs. As the temperature outside has dropped, the moths have basically stopped. My plan was to throw away the traps over the winter, when the months weren't around, but, after reading your story, I think I'll throw them out today!!

Wow.