I found that my bag of chook grain is now full of Grain Weevils! I thought they were ants at first so didn't worry about it. It seems they lay their eggs in the grain and then continue to multiply. Apparently you can kill them by freezing or heating the grain. Maybe on the next bag I should divide it up in to small batches and freeze it for a week. They look like this.... (not my photo), about the size of a small ant.