Stonefly Species Sweltsa revelstoka (Sallflies)

Length to wing tips: 4–10 mm in males, 5–12 mm. in females; brachypterous or long winged. Length of body: 7-8 mm in males, 9-11 mm in females.

General color yellow tinged with brown. Head and discs of pronotum with brown markings and rugosities, very much as in Sweltsa borealis Banks and in Sweltsa fidelis Banks; sides of pronotum margined in black; mesonotum and metanotum with dark U-marks. Abdomen with dorsal stripe on first eight segments, yellow ground color of abdomen suffused with brown. Antennae, cerci, and legs yellow brown.

MALE: Supra-anal process extending across ninth tergite to raised, notched tubercle on eighth tergite, expanded near middle to about 1.5 times width of basal third of process; in lateral view tip of process is slightly upturned, figure 10.

FEMALE: Subgenital plate produced into broadly rounded lobe extending across anterior half of ninth sternite, square notch medially, figure 10A.

This new species is similar to Sweltsa fidelis Banks, Sweltsa borealis (Banks), and Sweltsa continua Banks. From Sweltsa continua it is readily separated by the head color pattern and the shape of the genitalia in both sexes. From Sweltsa fidelis it is distinguished in the male by a slight difference in shape of the supra-anal process in lateral view (figures 10 and 11), and in the female, by the notched subgenital plate. In the male the shape of the supra-anal process in both dorsal and lateral view separates this new species from Sweltsa borealis, and in the female the distinctly square notch with no central lobe in the subgenital plate distinguishes it. (At least a suggestion of a lobe in usually present in Sweltsa borealis). At Still Creek, Mt. Hood, Oregon, this species occurs at a higher elevation than does Sweltsa borealis and it is noticeably smaller and brighter in color.