This is the smallest stonefly I've ever collected, with a body only 5.5 mm long.
Although not in-focus in my pictures, its first
tarsal segment is similar in length to the third, while the second is much shorter. This helps with family-level identification.
Examining this specimen under a microscope shows a membranous lobe on the
dorsal base of the
cerci, which is the key characteristic in Merritt & Cummins (4th ed.) to place the genus definitively as
Malenka.
Following the species key in Jewett Jr's
Stoneflies of the Pacific Northwest, the species appears to be
Malenka tina. My dissecting microscope seems to show
sternite 9 ending in a rounded knob, which distinguishes it from
Malenka bifurcata, but the detail is hard to work out.
Also worth noting is that Montana appears to have this species, whereas
birfucata is not know there: http://fieldguide.mt.gov/displaySpecies.aspx?family=
Nemouridae