Grain maggots and the resulting adult beetles or moths come from the eggs
that are present all of the time in all grains and flours - processors
cannot remove them. Ziplock bags cannot prevent them. Only proper storage
can prevent them from hatching out. Refrigerate or freeze all grains and
flours and meals - even cornstarch. Even processed products like cereals,
unless quickly eaten, should be kept cold. Spices can also become infested
at the right temperature and humidity. You'll recognize it when the leafy
spices cling together as if in a web - which it is. Buy small quantities
and date your containers - at six months they'll start getting a little long
in the tooth . . . :-)
Living in the warm (usually), humid South, I learned quickly how to wage war
on the smalls.
Martha