The Little Dirty Yellow Hendrickson

The first pattern, a Poster: The Little Dirty Yellow Hendrickson
The Jave Quill version of the LDYH in a CDC dun pattern awaits testing.

I have been doing my mayfly research for the next hatch I hope to be fishing, and the more I read from my references the more interesting things have become. I first encountered the mayfly I dubbed the Little Dirty Yellow Hendrickson on the Mainstem Delaware in 2019, then my friend John and I plucked a few from the waters of the West Branch during a float trip that same spring. They showed up after the main Hendrickson hatch was over, though the first duns I got my hands on certainly looked like Hendrickson duns to me, though smaller duns of a decidedly different color.

Once upon a time, if you went into a fly shop for a package of sulfur dubbing, you got a fur blend that was reminiscent of sulphur, a dirty, dark yellow with a golden overtone. Where I fished, sulfurs were a major hatch, but they varied from a fairly pure sunny pale yellow to a pale yellow/ pale orange mix, like most of the sulfur dubbing you see today. When I first captured the “new” mayflies, I dug out a thirty year old package of Orvis sulphur yellow dubbing and started blending from there.

My name for these size 16 mayflies was purely descriptive. They had the gray tails and fairly dark gray wings of the Hendricksons, along with the same distinct rather blocky thorax. The back of the abdomen and thorax shared a dirty gray tone, and the underside was that darker, dirty, sulfurious yellow.

In talking with fellow anglers, several chimed in with an “oh, those are Invarias”, meaning Ephemerella invaria, commonly called Big Sulfurs. I accepted that for a while, until I did a little bit of research and decided these were not E. Invaria mayflies. Angler, author and Catskill legend Al Caucci maintained that he and Hatches co-author Bob Nastasi had sampled several different unidentified species of mayflies in the Delaware system that appeared to be closely related subspecies of the Hendrickson (Ephemerella subvaria), some of which they referred to as Ephemerella X. From Caucci’s description, I don’t think these are his X bugs, but I do believe they are Hendrickson relatives. I will stick with Little Dirty Yellow Hendrickson or LDYH (Lady H).

Though I have more curiosity regarding the science, I am not an entomologist. I am a fly fisher, and I have the knowledge I need to find them, tie them and fish them effectively, whatever species they may actually be.

The Poster pattern above is the first pattern I tied to imitate the Lady H hatch, and it has been well proven on a number of selective trout. Best of all, I landed a pair of two foot long wild browns on that fly last spring. I tie a parachute version too with the same materials.

Since I started seeing these duns coincident with the apparent end of the Hendricksons this week, I gathered the appropriate flies into one box, and then decided to try a quill bodied version of the CDC duns that have been some of my top flies this spring. The Jave Quill Lady H should be a killer as well. Just to be safe, I tie a few of my patterns in a size 14, though most of them are 16’s.

Perhaps one of these days I will make the acquaintance of an active professional entomologist who will know the species of this mayfly, or take a few back to his DNA lab to solve the mystery. It does seem that every time those guys do DNA tests they rewrite about a century of accepted fly fishing literature in regards to hatches, something I am not necessarily in favor of. After all, does it really matter all that much if we have a brand new Latin name for the bug tied to the end of our line? If we know the appearance, habits and habitat to encounter these mayflies, then we ought to be able to have some success fishing the hatch.

I kind of like Lady H as opposed to Ephemerella schmotium delawarus once Dr. Joe Schmo actually identifies and names this new species anyway.

One thought on “The Little Dirty Yellow Hendrickson

  1. I too have noticed this curious little, unidentified mayfly. It’s been a true pleasure to take part in an expert’s unpacking of such a peculiar finding.

    How outré a thing. This scattered spice of life we dub the mayfly.

    For heavens sake, will someone contract an active professional entomologist to take these samples back to his or her lab for identification and classification? With this, I could not agree more.

    We count on you sir to pursue this valiant quest towards greater understanding, BUT pray keep in mind the long unadulterated history of these great waters and all existing literature in your doing so.


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