Preheat oven to 350 ºF. Grease muffin pans or line with paper baking cups.
Combine cake mix, egg whites, water and oil in large bowl. Beat at low speed with electric mixer until moistened. Beat at medium speed 2 minutes. Fold in 1/3 cup star decors. Fill muffin cups about 2/3 full.
Bake at 350 ºF. 18 to 23 minutes or until toothpick inserted into center comes out clean. Cool in pans 5 minutes. Remove to cooling racks. Cool completely.
Tint vanilla frosting with green food coloring. Frost one cupcake. Sprinkle 1/2 teaspoon chocolate cookie crumbs on frosting. Arrange 4 candy-coated chocolate pieces to form caterpillar body. Place jelly bean at one end to form head. Attach remaining star and nonpareil decors with dots of frosting to form eyes. Repeat with remaining cupcakes.