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