During April the Hennies should be coming off in large numbers. In anticipation and preperation for this I am re-visiting both my online resources and the books I have to re-aquaint myself with one of the areas, and one of fly fishings most well known hatch, the Ephemerella subvaria.
1st lets discuss water temperature: ideal hatching conditions will, according to my sources, occur between 2-4pm when the water temp rises between 50-55 degrees. It should be noted that on hotter days the time may extend to later in the day when water temps decrease back into the 50-55 degree range.
2nd when imitating the nymphs of Ephemerella subvaria the size is important. The naturals that I took from streams in our area averaged about 11mm, this may be 1mm short, my book states 12mm and that sounds right seeing that these nymphs still have time to develop. The book source I’m using is Hatches 2 by All Caucci and Bob Nastasi which recgonizes that within Ephemerella subvaria there are several color variations and that you should tie yours according to the naturals you find in your streams. The ones I’ve collected recently were dark brown with hints of red, also these nymphs are much wider and thicker than say the Baetis nymphs that you might find.
For dry flies I’ve read and been told that size 14 is the most common size for the Dark Hendrickson in S.E. MN. They are tied in various colors with different wings/post. I tied these with a golden brown Antron wing, other options are lemon wood duck or dun antron. I’ve seen the body as dark brown, grey and the hackle as dun or brown/both. I used dun. I hope these serve me well.