This elegant species may produce fishable hatches. Where & When
» Species pulla (Golden Dun)
Regions: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.Nymph BiologyCurrent Speed: Slow to medium; sometimes riffles
East, MidwestTime Of Year (?):
June to October
Substrate: Detritus (Detritus: Small, loose pieces of decaying organic matter underwater.)
Pictures of 3 Mayfly Specimens in the Species Heptagenia pulla:
Heptagenia pulla (Golden Dun) Mayfly Nymph
View 5 PicturesI 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.) Heptagenia pulla (Golden Dun) Mayfly Nymph
View 11 PicturesThis 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 (Tarsal claw: The claws at the tip of the tarsus, on an insect's "foot.") has a single basal (Basal: close to the base; root or beginning) tooth, and the gills on segment 7 have fibrils.
For the species key:
1. The left mandible (Mandible: The paired jaws of an insect which are used for grabbing food, located immediately behind the labrum.) is planate (fairly straight-edged) whereas the right mandible (Mandible: The paired jaws of an insect which are used for grabbing food, located immediately behind the labrum.) is angulate (has one sharp turn on the edge).
2. The labrum (Labrum: The platelike structure forming the roof of the mouth of insects; the upper lip.) is much wider than long.
3. There's a thin light-colored streak lateral (Lateral: To the side.) to the eye on the head.
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