Shiny black beetle, oblong-rounded, flattened body. Collected. Locally common in shallow water, especially mats of aquatic plants, at the cobbly margins of recently constructed stream channel, in water a few centimeters deep. At least 30 present in a 10 meter stretch. Stream floodplain disturbed in winter 2020-2021 by heavy equipment during stream restoration work. Large patches of bare ground, stands of exotic perennial grasses re-establishing, large patches of Chenopodium simplex and C. berlandieri with many ripe seeds, and patches of still-flowering Helianthus annuus and Sisymbrium loeselii. Early night, the first few hours after sunset. Smoky, wind calm varying to light breeze, partly cloudy, 75 F to 64 F.

Elevation ca 4000 feet. Disturbed riparian corridor on stream restoration site within a patchwork of native and non-native grassland.

Keyed to genus in Arnett & Thomas 2001. Some of the characters include metatarsal claws equal; scutellum visible; medium size; pronotum with lateral bead; and the ) ( shape of the metacoxal lines. Have requested Larson & Wolfe 1998 and will attempt to key to species when I get it. Placing at the family level for now since I'm not sure if Arnett & Thomas' Agabus corresponds to the current treatment.