Fresh flour is pre-sifted at the mills and requires no checking.  However, if the flour is more than six weeks old or has been opened it may be subject to insect infestation. Therefore if even one weevil is visible then the flour must be thoroughly sifted before use or else discarded. If, however, the flour is fresh and no weevils are visible no sifting is required.
This applies similarly to barley, rice and other grains and beans available in Australia.