Lets Talk Bugs
by Tom Lager

I imagine most of you had a chance at the Ephoron leukon hatch this summer. My observations and comments from others indicate a "normal" hatch, but without significant fishing success. I guess success has variable meanings within the fishing community. I actually went out this summer with the intention of watching the emergence as opposed to fishing, largely because river temperatures were too high and potentially detrimental to trout, if fished.

In past years, I experienced "snowfall-like" emergences, the white flies swirling low over the water in a frenzied upstream / downstream fashion, typically within two - three feet of the surface. If you have attempted to handle them, you have found them to be very fragile and difficult to hold, as shown in the blurred photo above. I netted them, but their wings easily collapse making their form difficult to examine.

These creamy-white mayflies are essentially on a one flight mission. They emerge around 8:30 p.m. in late July through early August and are on the wing until darkness, living only several hours as an adult. Molting from the dun stage to the spinner stage occurs immediately after emerging from the nymphal husk. Some say, molting occurs during flight, which I find hard to believe since the process would interfere with flying as the wings shed their covering. Duns land on any available surface, fly rods, eye glasses, hats and vests, making it ease to see them shed and then resume flight as a spinner. Some spinners fly with the molt materials still attached to their tail filaments. Close observation shows legs are poorly developed (short in length and thin in diameter) when compared to other mayflies. This limited development is probably related to the fact that adults have limited use for legs. Legs are needed momentarily for only two functions, landing to molt and for males grasping the female during mating. These adults can not even feed since mouth parts are not functional. Basically, the Ephoron adult is designed for one brief flight, mating and dying in a time span of a few hours. Males likely live a little longer than females as they swarm in a patrolling formation over a limited stretch of stream and mate quickly with females that fly through the swarm. The females fall to the stream to lay eggs and die; males remain in swarming behavior until their death.

The nymph, shown in diagram below, live in the soft shifting sandy bottomed rivers. They are physically well developed in form similar to many other burrowing mayflies like Hexagenia and Ephemera. Their behaviors and feeding practices are also similar to these mayflies; however, they likely occupy different micro habitats such as current speed, substrate particles size and mixtures of materials (i.e. organic detritus and sands).

Ephoron leukon is an important mayfly for Wisconsin trout fishers. A number of dun, spinner and nymph patterns are common in our fly pattern literature and fly boxes. The nymph patterns used for Hexagenia and Ephemera in smaller sizes will work well. Do you remember Tex Helm's adult pattern? It was simple and effective.

I like using this hatch as an introductory experience for new trout fishers (when rivers are not over heated) because the emergence is a spectacle in it's timing and intensity and trout, if not shiners, love to feed on these mayflies. It is a great way to spend an August evening with a friend; perhaps at stream side with a glass of merlot for taste, a bit of Shelley for contemplation and the sound of leukon wings……

"He sets, and each ephemeral insect then

Is gathered into death without a dawn"

Percy Bysshe Shelley

After the hatch, it is quiet as we walk upstream to the covered bridge. We have been part of His rhythm … His creation. We know the act will replay tomorrow evening, again and again. As before, remember as you traverse our streams in search of trout, "take the time to pick up the rocks and look at the bugs".