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.
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Mayfly Species Heptagenia pulla (Golden Dun)
This elegant species may produce fishable hatches.
Where & when
There are conflicting accounts of the emergence dates for this species. The Leonards in Hatches II give June 2nd to August 4th as the dates for emergence in Michigan, while Caucci and Nastasi in Hatches II say it hatches from August through October. Knopp and Cormier say it hatches from mid-May through August. I don't know who is correct, but I have collected near-mature nymphs in June in northern Wisconsin.Specimens of the Mayfly Species Heptagenia pulla
3 Nymphs
Like most Alaskan mayflies, this one is tricky to identify to the species level. See the discussion section for an informative chat about this one's ID. The current leaning is to call it a fairly immature Heptagenia pulla nymph, but a case has been made for Heptagenia elegantula as well.
I used a microscope to positively identify this nymph as Heptagenia pulla. (Edit six years later: I wish I had explained why I was positive about this. It may have been based on color patterns in an angling text, which are not especially reliable for species ID anymore.)
This specimen is interesting because Heptagenia pulla has not been reported from Washington or neighboring states (Saskatchewan is the closest), yet the distinctive key characteristics are clear.
It keys to the genus Heptagenia because the tarsal claw has a single basal tooth, and the gills on segment 7 have fibrils.
For the species key:
1. The left mandible is planate (fairly straight-edged) whereas the right mandible is angulate (has one sharp turn on the edge).
2. The labrum is much wider than long.
3. There's a thin light-colored streak lateral to the eye on the head.
It keys to the genus Heptagenia because the tarsal claw has a single basal tooth, and the gills on segment 7 have fibrils.
For the species key:
1. The left mandible is planate (fairly straight-edged) whereas the right mandible is angulate (has one sharp turn on the edge).
2. The labrum is much wider than long.
3. There's a thin light-colored streak lateral to the eye on the head.
Recent Discussions of Heptagenia pulla
Comment on Heptagenia pulla:
You can quickly and easily register to post comments.References
- Caucci, Al and Nastasi, Bob. 2004. Hatches II. The Lyons Press.
- Knopp, Malcolm and Robert Cormier. 1997. Mayflies: An Angler's Study of Trout Water Ephemeroptera . The Lyons Press.
- Leonard, Justin W. and Fannie A. Leonard. 1962. Mayflies of Michigan Trout Streams. Cranbrook Institute of Science.
Taxonomy
Kingdom
Animalia (Animals)
» Phylum
Arthropoda (Arthropods)
» Class
Insecta (Insects)
» Order
Ephemeroptera (Mayflies)
» Genus
Heptagenia
» Species pulla (Golden Dun)
Species Range
Common Names
Resources
- NatureServe
- ITIS
- Described by Clemens (1913)