Pale Morning Duns

Ephemerella dorothea infrequens (formerly Ephemerella infrequens), together with its smaller sibling Ephemerella excrucians, make up the most important Western hatches. They go by several common names but are best known as Pale Morning Duns (PMD's). They are rivaled only by the many baetid species that typically bookend them. In terms of availability, consistency and abundance (not to mention their convenient timing and preference for beautiful weather), they have no rival. There is considerable evidence that on temperature stable spring creeks they can have asynchronous emergences in the spring and fall, not to be confused with many baetids multivoltine (Multivoltine: Having more than one generation per year.) life history (Life history: The detailed life cycle of an organism, including the stages it passes through and characteristic behavior relating to growth and reproduction.). They can run in size from a large 16 to a small 12 and various shades of illusive yellowish creams, sulfurs, and even olivacious greens, depending on the system they inhabit.

This taxon used to be considered the separate species Ephemerella infrequens, but entomologists now regard it as a subspecies (Subspecies: Entomologists sometimes further divide a species into distinct groups called subspecies, which have two lower-case words on the end of their scientific name instead of one. The latter is the sub-species name. For example, Maccaffertium mexicanum mexicanum and Maccaffertium mexicanum integrum are two different subspecies of Maccaffertium mexicanum.) of the same species as the small Eastern sulphur hatch Ephemerella dorothea dorothea. There is another related listing of significance common in California and the Southwest that has undergone revision. The substantially larger (often exceeding 10 mm) Ephemerella mollitia is now considered synonymous with dorothea infrequens.

While it is not the normal policy of TroutNut to list subspecies (Subspecies: Entomologists sometimes further divide a species into distinct groups called subspecies, which have two lower-case words on the end of their scientific name instead of one. The latter is the sub-species name. For example, Maccaffertium mexicanum mexicanum and Maccaffertium mexicanum integrum are two different subspecies of Maccaffertium mexicanum.) as separate taxa, dorothea infrequens and dorothea dorothea are so important and distinct from each other in terms of geography and angling tradition that they warrant an exception.

For anglers, this single species is arguably the most important mayfly in North America. In terms of sheer numbers, breadth of distribution and hatch duration, it has a good argument.

Ephemerella excrucians or Pale Morning Dun usually follows its larger sibling Ephemerella dorothea infrequens with which it shares the same common name. What it lacks in size by comparison is made up for with it's duration, often lasting for months with intermittent peaks. This close relationship with infrequens has led many anglers to confuse Pale Morning Dun biology with that of the multivoltine (Multivoltine: Having more than one generation per year.) Baetidae species, having disparate broods that decrease in size as the season advances. Sharing the same common name has not helped to alleviate this misconception.

Until recently, Ephemerella excrucians was considered primarily an upper MidWestern species of some regional importance commonly called Little Red Quill among other names. Recent work by entomologists determined that it is actually the same species as the important Western Pale Morning Dun (prev.Ephemerella inermis), and the lake dwelling Sulphur Dun of the Yellowstone area, (prev.Ephemerella lacustris). Since all three are considered variations of the same species, they have been combined into excrucians, being the original name for the type species reported as far back as the Civil War. Speculation had simmered for some time that the stillwater loving Ephemerella lacustris was much more widespread, inhabiting more water types then previously thought and could account for many sulfurish Ephemerellids found in locations throughout the West. With the revisions, this discussion is now mute.

Ephemerella excrucians variability in appearance, habitat preferences, and wide geographical distribution are cause for angler confusion with the changes in classification. One could fish a hatch of creamy 18's on a Calfornia tailwater, an olivaceous 16 on an Idaho freestone, a sulfur 14 on a Yellowstone lake, and a little Red Quill on a small stream in Wisconsin, yet all are the same species.