Entomology (Study of Bugs)/House Moths
I too found larvae and small moths in an unopened package of napkins. We were traveling and my grandson called to let us know we have bugs in our cabinet. As soon as we got home, we checked the cabinet. Found many moths but also found the source.
The napkins. The only food in that cabinet was a can of coffee,
covered dish of butter, a jar of peanut butter and a small jar of honey. Mainly a dish cupboard. Cleaned three times, washed all dishes, microwaved bread baskets, etc. Sprayed all cracks and crevices with raid and left closed for 3 days. Washed cupboard again and put dishes back. A few days later, more moths.
Found one larvae and one moth in a cereal cabinet. Cleaned, checked cereal and never any more in any food cabinets. Found moths behind refrig. Scrubbed and cleaned everything. Got traps and caught more. No more in kitchen but in our bedroom, bathroom and our computer room. Today, I found them in the attic. No food in any of these rooms but 40 to 50 male moths in each trap.
Don't understand why they did not get in cabinets with cake mixes, etc. I have filled four traps upstairs and putting out more. Is there anything else I can do to get rid of these pests?
These are probably one of the meal moths, perhaps the Indian meal moth (see http://www.livingwithbugs.com/mealmoth.html
for pictures). You are doing the right thing .. trying to locate the source, using the moth traps will help. My guess is there is a grain source somewhere in the house that may not be obvious such as an old bag of birdseed or pet food that has been forgotten. Keep searching especially where you trap the most moths and you'll eventually find the source.