Spooner, know anything about the life cycle of insects? In the first place, worms aren't bugs. Worms are worms. Bugs, on the other hand are insects. The life stages of insects are egg larva pupa and adult. If you get a bag of potatoes with the eggs of some insect in it you won't see anything. but when the eggs hatch, time passes here, they hatch out into voracious worm like things called larvae, that eat and eat and eat and get big quick. Then the pupate, like a butterfly chrysalis, undergo metamorphoses and hatch out as adults. If the worms you have are fly larvae, flies fly places when you're not looking and may have found your old potatoes starting to turn into tasty fly food and laid their eggs right in your cupboard.