The horsefly bites hard and persistently, read as someone or something that keeps provoking you. Old tradition’s gadfly also stands for a needling critic who will not let you rest.
Does the traditional reading fit your dream, or did it mean something else to you?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.