This might be an urban myth? But I have never licked an envelope since someone told me some had been stored where cockroaches clambered over them and it led to unpleasant cockroachey stomach upsets.Due to people licking cockroach urine.

The same woman though also told me that once, she had just finished brushing her teeth and when she put the brush back in the beaker, she saw little beetle legs wriggling in the bristles, and the rest of the beetle looking very foamy embedded in the tufts.Always worth a double check now.