Don't Bring a Green Drake to a Hex Hatch

As the Hex hatch makes its annual march across the U.S., a spate of articles on how best to match these giant flies made their appearance this past week. First there was Eric Sharp telling folks not to tie their flies too big: Hexagenia limbata are not the size of small airplanes.
Then Ken Allen wrote a characteristically detailed piece in the Kennebec Journal on hex hatches and how they fit into the Maine fly mix, where they are often confused with green drakes: “The sole big deal about misnaming the bug strikes anglers with entomological knowledge as obvious. A true green drake (Ephemera guttlulata) is a different size and color than a Hex, so if you tell a fly fisher – say from Pennsylvania or even Portland – that he or she should bring Green Drake dry flies to a Hex hatch, the chosen pattern will be smaller and much greener than a Hex imitation.”
Finally Paul Reynolds queries Eastern Hatches author Tom Fuller, whose answer on differentiation makes it apparent why the mistake is often made. “The differences between the Eastern Green Drake (3 tails on the dun) and the Hex hatch (two tails on the dun) are at best subtle. The Eastern has mottled wings, the Hex doesn’t have the mottling, but does have veins. Coloration and size really depend on the waters where they’re found and the fertility. The real difference is the double gills found on body segment #1 on the Hex. The Eastern nymph has single gills on body segments 1 through 7.”
As if standing in water up to your navel at midnight weren’t enough to keep the mind agile.