Place cereal in a mixing bowl; set aside. Place a piece of wax paper on countertop. In a saucepan, combine candy, milk, and pumpkin pie spice, stirring frequently. Mix until smooth. Pour mixture over cereal in bowl, tossing to coat all sides. Chill for ten minutes, or until easy to handle. With wet hands, form cereal mixture into three inch balls to resemble pumpkins. Place a small green gumdrop on top of each to form stem. Pipe icing in lengthwise lines around side of balls to resemble crease in pumpkins.