I like looking at the movie with the bug motif. It helps to make sense of the whole thing as it seemed that the plot was kind of iffy and the bugs are present from the beginning, in the middle, and at the end of the movie.
Also lets not forget that after the scene with the bugs underneath the surface crawling with life, there are more bugs. When Jefferey finds the severed ear there are ants crawling all over it, which could be seen as a clear indication that the same unpleasant ugliness that is hidden behind the picturesque perfect town facade, is also behind the severing of this ear. They are the same people who are tormenting the owner of this ears family.