The famous nocturnal Hex hatch of the Midwest (and a few other lucky locations) stirs to the surface mythically large Brown Trout that only touch streamers for the rest of the year.
This species is very similar to Drunella flavilinea. In areas where their ranges overlap, they can sometimes be found in the same streams. Allen and Edmunds (1962) say that Drunella coloradensis tends to favor colder water than Drunella flavilinea and that it may emerge as much as a month later.
Where & when
Time of year : July to early October
Preferred waters: Small streams
Altitude: High
According to Fred Arbona, this species requires streams which never exceed 60°F, and this limits them to small streams at high altitude.
Specimens of the Mayfly Species Drunella coloradensis
This one nicely illustrates the variation in coloration within an single Ephemerellid species in a single stream, when compared to its lighter, banded counterpart.
This one nicely illustrates the variation in coloration within an single Ephemerellid species in a single stream, when compared to its darker, more uniform counterpart.