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Lateral view of a Male Baetis (Baetidae) (Blue-Winged Olive) Mayfly Dun from Mystery Creek #43 in New York
Blue-winged Olives

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.

Lateral view of a Psychodidae True Fly Larva from Mystery Creek #308 in Washington
This wild-looking little thing completely puzzled me. At first I was thinking beetle or month larva, until I got a look at the pictures on the computer screen. I made a couple of incorrect guesses before entomologist Greg Courtney pointed me in the right direction with Psychodidae. He suggested a possible genus of Thornburghiella, but could not rule out some other members of the tribe Pericomini.
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.
Troutnut is a project started in 2003 by salmonid ecologist Jason "Troutnut" Neuswanger to help anglers and fly tyers unabashedly embrace the entomological side of the sport. Learn more about Troutnut or support the project for an enhanced experience here.

Mayfly Genus Heptagenia

Although still an important genus in its own right, Heptagenia no longer includes many of the key hatches it used to. Several important species have been moved to its sister genera Nixe, Leucrocuta, and Ecdyonurus.

Of the remaining species, the best hatches come from Heptagenia elegantula in the West. The genus is generally unimportant in the East and Midwest, where the most likely species to produce fishable hatches is Heptagenia pulla.

Where & when

In 159 records from GBIF, adults of this genus have mostly been collected during June (30%), July (26%), August (16%), May (12%), and September (8%).

In 115 records from GBIF, this genus has been collected at elevations ranging from 3 to 11001 ft, with an average (median) of 4675 ft.

Genus Range

Hatching behavior

Heptagenia nymphs emerge very quickly, so emerger patterns are unimportant. The duns may or may not float long enough to get trout excited.

Spinner behavior

Spinner falls give the most promising action produced by Heptagenia species.

Specimens of the Mayfly Genus Heptagenia

1 Male Dun
4 Male Spinners
5 Nymphs

Discussions of Heptagenia

Added more Heptagenia culacantha info
12 replies
Posted by Troutnut on Dec 19, 2006 in the species Heptagenia culacantha
Last reply on Feb 8, 2012 by Entoman
I went to the entomology library today and photocopied the 1985 paper that first described this curious species. I've updated the culacantha page with this information.
Link to pictures of H. culacantha
2 replies
Posted by Troutnut on Oct 20, 2006 in the species Heptagenia culacantha
Last reply on Oct 4, 2007 by Troutnut
Many thanks to user Softhackle for digging up this link. I knew about the thread from back when it started, but I wasn't able to find it when I went back to look last night. Good work!

Fly Fisherman Magazine forum topic with two pictures of a H. culacantha dun.

I've added the species to the "live" part of the database and put up a rudimentary page where I can compile any more information we find.
Does anyone know anything about Heptagenia culacantha?
8 replies
Posted by GONZO on Oct 19, 2006 in the species Heptagenia culacantha
Last reply on Apr 18, 2007 by Konchu
This is a shot in the dark, but I'm trying to track down descriptive information about a rather rare "mystery mayfly." Heptagenia culacantha was identified in 1985 (Evans, Botts, & Flowers). About all I have right now is a tease from the Journal of the New York Entomological Society--"This infrequently taken species, one of the largest and most striking North American heptageniids, is known only from Pennsylvania and New York."

The reason I'm so interested is that I believe I encounter a fishable hatch of these mayflies every season on one of my favorite PA brook trout headwaters. If that conjures a picture of fishing to 6-7" dinks, you'll need to double those numbers to appreciate how special this stream really is. Add to that an image of the fish rising to these beautiful "mystery mayflies" that hatch in the evening, following a day-long emergence of Dark Green Drakes (Litobrancha recurvata)!

It is such a special event that it is one of the very few things that can pull me away from fishing my favorite Olive Morning Dun hatch (Drunella lata, nee cornuta). Help!

Start a Discussion of Heptagenia


Mayfly Genus Heptagenia

Genus Range
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