A reader wrote to us recently about the small, black worms that are getting under the bottom of his sliding door. The worms are a persistent problem, as about 10 manage to get into our reader’s house every day. The reader didn’t ask what the small, black worms are, which is just as well because many, many creatures might be described as “small, black worms.” All he is concerned about is keeping them from getting under his door, which is to say he wants to get rid of the worms in his house, but doesn’t seem to have any desire to completely annihilate them (as often seems to the case with readers caught up in the midst of a worm problem). We therefore won’t focus on what the small, black worms are, but only on how to keep the worms out of the house.