Identification: Key to Families of Stonefly Nymphs, Couplet 2

I'm guessing this is an immature Peltoperla, because it lacks the well-developed setal fringe on the hind femora that would indicate Tallaperla, but it also lacks the dark spots that should indicate a mature Peltoperla nymph.

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

This Skwala nymph still has a couple months left to go before hatching, but it's still a good representative of its species, which was extremely abundant in my sample for a stonefly of this size. It's obvious why the Yakima is known for its Skwala hatch.

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.

(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.