In a few days we expect to start seeing Sulphurs in my area. A few days after there initial emergent the hatch should be fairly strong and steady on my home streams. This is one of the first Mayflys to come back in numbers after a polluted stream that returns to a cleaner state. There are three species of them but I will not get into there scientific names. Just remember most are a orangish yellow but some can have a chartreuse colored body The duns have a cram-ginger tail and legs with a smoke colored wing. When they turn into a spinner the wings are basically clear. There size varies from a size 12 hook to a size 16 hook. If you live in a northern area from South central Pa they can start to emerge in late May through June. Do not hesitate to swing wet flys as some of the species can swim and will swim to the surface when they are hatching. This is one of my favorite hatches as the weather and water is usually perfect for fly fishing.