As we move into May, there will be very few river fly fishers who aren't looking forward to the bonanza that is the 'Mayfly'. The appearance of Ephemera Danica on our waters is always a prized time. Whether it is fish slashing at newly emerged duns or the rhythmic picking off of spent spinners, it is a special time on our waters. Although my first Danica of the year has been spotted already, it's the last couple if weeks of May into the beginning of June that offers the best of the hatches…