Oh - and they eat glue as well - like the glue on envelopes. But it seems to be only on old, discolored envelopes for some reason. And you can tell they've been there because the glue or envelope looks kind of...nibbled.

And you don't have to throw everything away - examine the packages. If they look undamaged, it's okay. If it looks like there are little tiny nibbles out of it, then throw it out. If it's in your refrigerator, it's safe.