Jun 24, 2013 - 12:24 PM
That is a hard question to answer, because legally, in most states, you also cannot spray for an insect that you cannot visually identify. In other words, there has to be a target pest, and if you spray something without a specific target pest, you could be in violation of that pesticides label directions, and or state or federal law.
We have a page on insects you can't see here - http://www.epestsupply.com/bugs-insects-you-cant-see.php#.UcicGDu-phA
I will tell you that it sounds like either clothes moths, silverfish, or even dryer damage. If you cannot find any evidence of any dead insects, then I would look for any source. In almost all cases of insect infestation, you will something that will indicate what it is.
Moth balls in my opinion are smelly, and don't work. Try putting out some ePest IPM Bug Traps, or a Clothes Moth trap, maybe a couple of each in the closet and see what you capture. It can't hurt, and if you don't catch anything, it is probably mechanical damage.