Make the spicy pecans. Heat oven to 325 degrees. In a small bowl, mix together pecans, melted butter, Worcestershire sauce, 1/2 teaspoon salt, chili powder, 1/8 teaspoon black pepper, and cayenne pepper. Pour onto a baking sheet and place in oven for 10 minutes. Stir and continue to bake 5 minutes. Remove from oven and let cool.
In a medium bowl, combine diced watermelon, red onion, arugula, and blue cheese crumbles.
Sprinkle pecans on top.
In a small bowl whisk together vinegar, oil, salt and pepper. Drizzle on salad.
If desired, portion salad onto watermelon wedges to serve.