1Heat oven to 350°F (325°F for dark or nonstick pans). Make and cool cake as directed on box for two 8-inch or 9-inch rounds. Wrap and freeze 1 layer for other use. Refrigerate or freeze remaining layer 30 to 60 minutes or until firm for easier handling.
2Using serrated knife, cut rounded top off cake to level surface; place cut side down. Cut cake in half; cut a notch on each cut side, slightly below center, to form wings as shown in diagram. To make butterfly, arrange 2 wings on foil-covered tray; use 2 of the leftover notched pieces to form the body, trimming if necessary. Attach pieces together with a small amount of frosting. Spread a thin layer of frosting over top and sides to seal in crumbs. Refrigerate or freeze cake 30 to 60 minutes to set frosting. Frost entire cake.
3Sprinkle with colored sugars. Outline wings and body with decorating gel. Decorate wings with assorted candies as desired. Roll fruit snack rolls to make antennae. Store loosely covered.