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Mayfly Species Ephemerella tibialis (Little Western Dark Hendrickson)

Pictures Below
Ehhemerella tibialis (Little Western Red Quill, Little Western Dark Hendrickson) is a common western species that can be very important at times. It is perhaps also one of the most confusing species. Unlike it's western generic counterparts the species is described as dark and their females produce dark eggs. Until recently, it was classified in the Serratella genus with species that share these traits. Regardless, it is the only small, dark ephemerellid the western angler is likely to find important. Favorite patterns used for size 18 Pale Morning Dun hatches tied in eastern Dark Hendrickson colors should be the ticket.

As with many of it's sister species it is widely adaptable and may be variable in its appearance. Scientific literature and many angling sources describe it as a small dark mayfly. Not everybody agrees. Ralph Cutter, West Coast author of several angler/entomology books and articles describes it in Sierra Trout Guide as a much larger pale mayfly and dubs it the Creamy Orange Dun. He also mentions the nymph as being easy to recognize by the faint dorsal (Dorsal: Top.) stripe running down its back and its often fiery brownish red color. These descriptions also match a variation of the ubiquitous and common Ephemerella excrucians.

Where & When

Region: West

Time Of Year (?): August to September

Altitude: Medium to high
Known distribution covers all the mountainous regions of the West excepting the California Coast. It is especially adaptable to many habitats.

Hatching Behavior

Time Of Day (?): Midday

Spinner Behavior

This is the only spinner (imago (Imago: The sexually mature adult stage of the mayfly is called the imago by scientists and the spinner by anglers.)) in the genus with dark blackish eggs. General consensus is these spinner falls are rarely important to the angler.

Pictures of 6 Mayfly Specimens in the Species Ephemerella tibialis:

Specimen Page:12
Female Ephemerella tibialis (Little Western Dark Hendrickson) Mayfly DunFemale Ephemerella tibialis (Little Western Dark Hendrickson) Mayfly Dun View 6 PicturesI'm fairly confident calling this dun Ephemerella tibialis because it emerged from one of several similar nymphs in my bucket, which I was able to ID with quite a bit of certainty. However, it looks very different from the other duns I currently have listed, which makes me rethink their IDs.
Collected August 3, 2020 from the East Fork Big Lost River in Idaho
Added to by Troutnut on August 18, 2020
Specimen Page:12

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