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. Furthermore, it might even be a species not listed on this site—Jacobus et al. (2014)
writes, "the northern and western specimens of H. pulla
may in fact be a synonym
of the Palearctic
species H. dalecarlica
Bengtsson (Kjaerstad et al. 2012) and the true H. pulla
may be restricted to eastern North America."
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 in Jacobus et al. (2014)
1. The left mandible
, whereas the right mandible
2. The labrum
is much wider than long.
3. There's a thin light-colored streak lateral
to the eye on the head.