bug boy
n.— «Around the racetrack, they are called “bug boys,” but not for their love of insects. These jockeys get their names because the Daily Racing Form used to print a “bug”—or asterisk—next to the weight assignments of apprentices. The more asterisks, the less experience and winners an apprentice had. They are the rookies of thoroughbred horse racing.» —“Del Mar: The apprentices” by Jeff Nahill in Inglewood North County Times (Escondido, California) July 16, 2006. (source: Double-Tongued Dictionary)