I believe they are weevils, they are harmless, and you will often buy flour with unhatched eggs in it making it impossible to avoid them. I regularly clean my cupboards with dettox etc but they always come back. I reckon they're pretty well impossible to eradicate once you've got them cos they'll hide in the tiniest of cracks and gaps in your kitchen cupboards and drawers. They only seem attracted to wheat based products though - they don't appear to be interested in rice or other dry goods. The idea of freezing flour is interesting, but I honestly believe you will still find them if you look closely enough. Rather than freaking out and having a wholesale purge and spring clean every time you spot one, just remember they are harmless, and just have a good clear out every 6 months or so to keep them under control.