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Lateral view of a Female Hexagenia limbata (Ephemeridae) (Hex) Mayfly Dun from the Namekagon River in Wisconsin
Hex Mayflies
Hexagenia limbata

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.

Dorsal view of a Ephemerella mucronata (Ephemerellidae) Mayfly Nymph from the Yakima River in Washington
This is an interesting one. Following the keys in Merritt R.W., Cummins, K.W., and Berg, M.B. (2019) and Jacobus et al. (2014), it keys clearly to Ephemerella. Jacobus et al provide a key to species, but some of the characteristics are tricky to interpret without illustrations. If I didn't make any mistakes, this one keys to Ephemerella mucronata, which has not previously been reported any closer to here than Montana and Alberta. The main character seems to fit well: "Abdominal terga with prominent, paired, subparallel, spiculate ridges." Several illustrations or descriptions of this holarctic species from the US and Europe seem to match, including the body length, tarsal claws and denticles, labial palp, and gill shapes. These sources include including Richard Allen's original description of this species in North America under the now-defunct name E. moffatae in Allen RK (1977) and the figures in this description of the species in Italy.
27" brown trout, my largest ever. It was the sub-dominant fish in its pool. After this, I hooked the bigger one, but I couldn't land it.
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Falsifly
Falsifly's profile picture
Hayward, WI.

Posts: 660
Falsifly on Nov 12, 2009November 12th, 2009, 6:14 am EST
“Good evening Mr. Brown, it’s good to see you. I’ve heard from many that you’re regarded as quite a sage along this stretch of river. Can you explain?”
“Yes, to put it quite simply it is because of my superior knowledge in aquatic entomology, more specifically, physiology.”
“I see, but could you explain in more detail? Many of us are very interested in your thoughts.”
“Well, maybe it would be best if I started from the beginning.”
“Please do.”
“My parents abandoned me just as life was beginning; a decision I now know was made at conception, leaving me to fend for myself. My childhood was fraught daily with all the dangers that the young ones, like me, were required to overcome in order to survive. Some solace was found hanging around with others my own age, but we were constantly being chased and harassed by the older neighborhood bullies, and the threat of bodily harm was ever present by those intent on inflicting just that. I think, from my earliest memories, night was the toughest part of the day to get through. It was then that my imagination took over and the bogyman always gained the upper hand, resulting in many nights of sleepless, restless, fear. I always welcomed mornings first light and the waning affect it had on the fear that darkness held. But daylight brought with it a different sense of fear, where the imagined was replaced with the real.
My early school days were a mixture of fun, and lessons learned. Lacking parental guidance, which we all as orphans shared, often led to mischievousness at its extreme. Very few of us, as did I, took life and our lessons seriously in an effort to succeed against all odds. Many of us bore the bruises and scars, some still evident today, inflicted upon us by those teaching the lessons. Those who failed to grasp the severity of the situation, and take to heart the lessons being taught, where plucked from our midst never to be seen again.”
“Well you certainly survived a very difficult and troubling childhood.”
“Yes, and that, as tough as it was, was only the beginning. It wasn’t until the following experience that I learned life’s most important lesson.
It was the first time that I’d experienced the Hex hatch. As word of the hatch spread like wildfire we assembled, in mass, upon the slow-moving silt-bottomed detritus-rich stretches of our home water. With frenzied enthusiasm we closely examined and plucked from the surface the plump proportioned duns as they slowly drifted downstream, feeding on the knowledge gained. As I approached one particular specimen, remaining cognizant of my discerning ability to identify even the slightest nuance, I noticed a peculiar appendage attached ventrally and extending posteriorly along the abdomen, as I moved in to add this specimen to my collection I was beaten to the punch. One of the others, in a gluttonous attempt not to be outdone, grabbed it before my very eyes. Let me tell you, the ruckus that resulted I have never before seen, nor will I ever forget. It spread a wave of fear into all of us, sending us scattering in all directions. What became of him, I know not, I’ve never seen him since. However, I have seen that funny looking appendage, many times over the years, and it, for whatever reason, has been the demise of many.”
“I see, so it was that funny looking appendage that gave you the first clue?”
“Yes, but my continued studies have revealed numerous idiosyncrasies in insect physiology.”
“Interesting, could you give us some more examples?”
“I’d be glad to. First and foremost is the funny looking appendage, which when spotted is the tip-off for closer examination. I’ve noticed extreme variations in length, abdominal segment count, and color wavelength. I’ve seen legs lacking tarsal claws, not to mention pectinations. I’ve witnessed unusual surface tension and buoyancy characteristics. Lack of movement, unusual movement, odd wing silhouette, anterior opaque attachments, is all too common, and I could go on and on.”
“It appears that you have quite a discerning eye.”
“Yes, a requirement to achieve a long life in these trying times. You’d be surprised at the increasing number of these oddities which pass by from year to year.”
“Do you ever find time for fun and games?”
“Yes I do, and because my life revolves around the insect I often make a game out of toying with the odd specimens. I enjoy rising and refusing, swirling, splashing, slapping with my tail and drifting varying distances with it balanced on the tip of my nose.”
“Thank you Mr. Brown, I certainly appreciate you showing up for this interview, and I hope to catch up with you in the future.”
“You are quite welcome, stop by anytime, I’ve given hundreds of interviews, and I assure you that I will be here.”


Falsifly
When asked what I just caught that monster on I showed him. He put on his magnifiers and said, "I can't believe they can see that."

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