Arugula Blood Orange and Blue Cheese Salad

8 cups arugula
½ cup blue cheese, crumbled
4 blood oranges, peeled, segmented and chopped
¼ cup olive oil
1/3 cup freshly squeezed lemon juice
1 tablepoon Dijon mustard
On serving plates, arrange 1 cup arugula on each plate.  Top with oranges and blue cheese.  In a small bowl whisk together olive oil, lemon juice and Dijon mustard.  Just before serving drizzle dressing over salad plates.  Season with salt and pepper.