A Musketeer Fly (マスケティア・フライ, Masuketia furai) is a flying insect wearing a fancy hat for some reason. It's bottom-half, as well as it's hands, resemble a horse and one's hoof. They are very skilled in fencing, being able to keep a duel going on for 3 hours, and if they get desperate, they will throw their sword. In addition, they are, for the standards of a usual fly, are enormous, sharing the same height as a common adult human.
Due to my lack of skill in drawing, i can't exactly show you what it would look like.