In a mixing bowl, combine blueberries with sugar, flour, nutmeg, cinnamon, lemon zest and juice. Pile into pie crust, mounding slightly in center. Dot blueberries with butter cut in small pieces. Roll out second section of dough. Cut into strips about 1 inch wide.
Place strips over pie, alternating horizontal and vertical strips.
Press the end of each strip into the edge of crust. Brush with beaten egg. Bake pie for 25 minutes. Reduce oven temperature to 350 degrees and cook until golden brown, about 30 minutes. Cool on a wire rack.