1. Frontoclypeus with two large upturned teeth or denticles on anterior margin (Fig. 1.1). . . . . 2
Anterior margin of frontoclypeus straight or convex; without upturned teeth. . . . . . . . . . . . . .3
2. Frontoclypeus typically with large V-shaped mark (Fig.1.2); entire posterior one-fourth of head yellow (Fig. 1.3); lateral and ventral, aspect of genae with little dark pigmentation, mostly yellow. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hydropsyche orris
Frontoclypeus with two large anterolateral spots (Fig. 1.4); wide dark areas adjoining epicranial arm; lateral, ventral, aspects of genae mostly dark with only a narrow yellow band behind eye. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hydropsyche bidens
Head dorsally with 2 large, conspicuous yellow spots (Fig. 1. X); head ventrally and laterally mostly yellow (Fig. 1.Y). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hydropsyche incommoda
3. Large, conspicuous and heavily sclerotized stout setae on venter of anal legs. . . . . . . . . . . . . 4
Large and heavily sclerotinized stout setae absent from venter of legs. . . . . . . . . . . . . . . . . . 8
4. Numerous black, bristle-like setae on posterior half of frontoclypeus. Stout spine-like setae on venter of anal legs more long and slender. Color pattern of head with 4 white spots anterior on a black background; posterior margin of head with teardrop shaped yellow markings meeting at coronal suture. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hydropsyche valanis
Posterior half of frontoclypeus lacking conspicuous stout, brinstle-like setae. Stout spine-like setae on anal legs sorter, stouter and heavier. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5. Head pattern light anteriorly and posteriorly with dark transverse pattern across middle area. All thoracic nota pale yellow. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Head pattern with more extensive brown pigment. I thoracic nota are pale yellow the pronotum is at least patterened and/or freckled with brown and darker than other thoracic nota. . . . . . 7
6. Stout, spine-like setae on venter of anal legs same size, shape, and color as those on ventral sclerites of ninth segment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hydropsyche aerata
These spine-like setae much smaller and less robust than those on venter of ninth segment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hydropsyche frisoni
7. Anterior half of frontoclypeus with two rows of large, yellow spots; first row with three spots, second typically with four; posterior half of sclerite mottled with brown. Hydropsyche patera
Frontoclypeus lacking two rows of pale spots anteriad. . . . . . . . . . . . . Hydropsyche scalaris
8. Posterior angle of frontoclypeus with elevated mound or tubecle best seen in lateral or prosterior view of head. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Posterior angle of frontoclyepus level with rest of posterior half of sclerite; no mound or tubercle present. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
9. Sides of head evenly curved; head typically unicolored dark brown to black except for light area around eye and occasionally behind eye. . . . . . . . . . . . . . . Hydropsyche depravata Group (There are two species in Ohio: H. betteni, throughout the state; and, H. depravata, mostly in southwest quarter of state)
10. Frontoclypeus with many stout, bristle-like setae conspicuous on body of sclerite; most abundant on posterhalf of sclerite. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Bristle-like setae, if present, restricted to anterolateral corners of frontoclypeus; posterior half of sclerite may have minute, clear, spine-like setae but lacks larger bristle-like setae. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hydropsyche dicantha
11. Frontoclypeus with two pairs of yellow spots, one pair centerally located, the other pair anterolateral to these; spots often fused to form large, diagonal streaks on anterior portion of sclerite; posterior half of sclerite mottled; in lateral view dark area behind eye with three to four horizontal rows of yellow muscle scars curved dorsad posteriorly; dark pigment behind eye contiguous with dark pigment ofn venter of head. . . . . . . . . . . . . . . Hydropsyche venularis
Frontoclypeus with single pair of centrally located spots; yellow muscle scars behind eyes not in rows; at least a narrow yellow band separating dark pigment behind eye and that of venter of head; posterior half of frontoclypeus solid dark brown, not mottled. . . . . . . . . . . . . . . . . . . 12
12. Dorsum of head dark brown with two small, often inconspicuous spots; venter of head mostly dark brown, except for two quadrate yellow spots adjacent to gular suture; pigmentation of dorsum and venter of head separated by yellow band behind eyes to back margin of head; area around eyes yellow. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hydropsyche hageni
Frontoclypeus dark brown with pair of large, conspicuous yellow spots; large, yellow areas on ventrolateral aspects of head. . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hydropsyche simulans
Key to Species of Hydropsyche Nymphs