Bugs, (generally those evil little moths I hate), thrive on flour, and you
can expect some to come in with every bag of flour, either live or in
larvae or egg form, unless the milling process uses some pretty nasty
chemicals. Bay leaves, etc. may work for some people, but the absolutely
foolproof method is to keep all flour in the freezer for several days. That
kills all of the crawlies, guaranteed. We had a bad infestation of moths
for a while and now keep all flours, grains, nuts and seeds in the freezer.
This worked. (The licensed exterminator, who we paid many dollars to for
monthly visits, did not work, I should note).
If you're asking how to get the insect parts out of the flour, don't ask
me. If the gov't says that a small percentage of crawlies is ok for human
health, who am I to argue? I just assume that it adds protein and vitamins
my body needs. Besides, it adds a frisson of danger and some medieval
authenticity to my historically correct sourdoughs. Better that than 1-2-8
bithialozamine hypochlorthiazide citrate, eh?