Though this will not be an appetizing post, it is necessary for any home baker to be aware of certain things. Wheat Weevils (Sitophilus granarius) are an unfortunate reality that must be dealt with.
First, I strive for total cleanliness in my kitchen and pantry. This includes weekly cleaning of my refrigerator. I typically store my flours at room temperature in air-tight containers. You store them in the freezer too, but I find this adds unwanted moisture and flavors to the flour. There is a good reason to store your flour in airtight containers (in the bag).
I picked up some King Arthur AP flour this weekend at my local supermarket. When I got home, I opened one of the bags and found it teeming with wheat weevils. My wife calls them “Gorgojos” which translates to “Weevils”. If you see these things in your kitchen, you have to immediately discard the flour. In my case, I put it in a zip top bag and took it back to the store for a refund, and to chastise the manager for having conditions in his storeroom that would allow such an infestation.
If you just store your flour on the pantry shelf, you are asking for a weevil infestation. I don’t know where they come from; I just know that you will get them. Many discount stores sell containers suitable for storing single 5 lb. bags of flour or even multiple bags. You need to invest in these if you plan to do any baking at home! At a minimum, keep your flour sealed in a plastic bag.
Remember this final warning…just because you buy new, fresh flour at the store doesn’t mean it is not infested with weevils. Always check it. You may not see any signs, but you will sometimes see an adult weevil when you open a new bag. If you find them in a new bag, return it to the store and speak to the manager. And most importantly, never again buy flour from this store! Chances are…the rest of their flour and wheat products (including wheat based kitty litter) is infested.