American March Brown Spinner

The American March Brown is one of the largest mayflies to hatch in the Eastern states and the Mid-west. Another common name for this mayfly is the Gray Fox. Like many of the mayflies, its hatches extend over a long period of time making it one of the more important mayflies. The spinners are the adult mayflies that fly and mate high in the air above the waters so they are easily seen by anglers.

The March Brown males are the first to fall to the stream or the bank followed by the females. The females however do not fall until their eggs have been deposited on the surface film on the water. Most of the males will fall on the banks, but the females will mostly fall in the water where they can collect in large numbers. Spinner activity starts in the calm of the evening a very great, and pleasant time for fly fishing.

Sometimes, the spinner fall is the most important aspect of the hatch, since the dun hatch occurs over a long period of time while the spinner fall concentrates the mayflies because it occurs in a shorter time frame. The females lay their eggs over the moderately flowing riffles and runs of the trout stream. After laying the eggs, the spinners will fall and the current will cause the spinners to collect in the usual pools and eddies.