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Tiny Baetis mayflies are perhaps the most commonly encountered and imitated by anglers on all American trout streams due to their great abundance, widespread distribution, and trout-friendly emergence habits.

Mayfly Species Ephemerella tibialis (Little Western Dark Hendrickson)

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 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

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) in the genus with dark blackish eggs. General consensus is these spinner falls are rarely important to the angler.

Specimens of the Mayfly Species Ephemerella tibialis

2 Female Duns
1 Male Dun
3 Nymphs

Recent Discussions of Ephemerella tibialis

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Species Range
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