Identification: Key to Families of Stonefly Nymphs, Couplet 7

This striking golden stonefly is the first of its species I've had the chance to photograph.

I'm not aware of any way to tell the two species of Doroneuria apart as nymphs, so this one is classified to species based on location alone. Doroneuria baumanni is found in the Cascades and in Washington, and the other species is not known here yet.

This is a difficult one. It keys convincingly to either Calineuria or Doroneuria. There is no mesal longitudinal row of silky hairs on thorax and abdominal dorsum, in either my pictures or anything I can see up close under the microscope. Lacking those hairs should indicate Calineuria. But abdominal sternum 7 has an incomplete posterior setal fringe, which would indicate Doroneuria, although the key says "usually" on that characteristic. For now I'm going with Calineuria, but it's far from certain. Maybe it's a younger Doroneuria and they don't grow that row of hairs until they're older. The markings on the head, especially the shape of the bright spot around the posterior ocelli, match online images of Calineuria californica better than Doroneuria.

(Edit: I'm putting a species ID on this one based on the great similarity of its markings to those of an adult I collected in 2023 from a tributary of the same river at around the same time of year.)

This one was tricky to identify. The "thick, depressed dark clothing hairs" on the thoracic sterna inside the coxae, which indicate Sweltsa, are fairly sparse and very difficult to see in my photos, although more apparent under the microscope. However, if I decide those hairs are too sparse to be "thick" and follow the key, I end up pretty clearly at Haploperla. However, Haploperla should have the inner margin of the hind wingpads approximately parallel to the body axis, and they're clearly divergent on this specimen. The pronotal fringe hairs should also be longer than they are in this specimen. So following that whole branch of the key was probably wrong, which leads back to this one being Sweltsa. Unfortunately, nymphs have only been described for a small number of Sweltsa species.

I found just a few of these nymphs alongside a much larger number of bland, typical Sweltsa nymphs.

This specimen represents a common find in a late-April sample from the far upper Yakima River. It seems to be the same species as another one I collected previously. Of the species keyed in Szczytko & Stewart 1979, it probably matches Isoperla fusca closest, but there's a good chance it's a species that wasn't in the key. The leg segments have a fringe of fine hairs which is supposed to be absent in Isoperla fusca, and the four dark stripes of the mesonotum and metanotum don't continue as 4 separate stripes on the pronotum as they should in the description of fusca. It's possible fusca is more variable than previously described, or this is a different species not included in that key. It's also worth noting there's definitely no fringe of fine setae on any part of the cerci, just the whorls of little stout ones around segment bases.

This species was fairly abundant in a February sample of the upper Yakima.