Size: 7-13mm

Seasonality: most active between April and late September

Distribution; BC, WA, OR, ID, nw. NV, MT, AB

Information: this carabid species is extremely variable in overall colouration, body length, and pronotum width, but is uniformly associated with bodies of water.   This carabid species may be found along the stony shorelines of lakes, rivers, shores bordering the Pacific, brooks, streams, creeks, etc.   Anchomenus aeneolus populations can be found on river islets, island/islets within lakes, and though colouration of their bodies are still heavily variable, the general appearance of the beetle tends to vary per location; i.e. those found along rivers, creeks, wetlands, and lakes in and around the Wallowa Mountains, are of a matte colour more often than not, while those which may be found in the Willamette Valley, and the Northern Rocky Mountains (BC), all have iridescent lusters.   This species is largely predatory, but may be omnivorous if necessary, generally live in groups of 30-200, generally will not be found huddled in one spot unless many are taking cover under something, or have found something edible.   A.aeneolus have been observed while eating the contents of various bird eggs which had fallen to the ground of been discarded from the nest.    Eggs generally are laid near the water, under stones, in damp soil. 

Description: body: elongate-oblong, moderately robust; flattish. Dorsal colouration highly variable, may appear as a variety of metallic or lustrous colours, semi-matte reddish-black, or matte greenish-grey or grey, nearing black. Dark matte specimens tend to be found in high desert areas. Ventral colouration glossy or matte black; legs black. Head triangular, elongate-slender; face long. Dorsal surface of the head smooth, with two small dimples on the frons; mandibles longish, curved; mandibles partially obscured by the labrum. Eyes not reduced in size, but do not strongly bulge laterally; two supraorbital setae over each eye. Base of the head weakly constricted into a slight neck. Pronotal shapes in this species are severely variable, as seen in the dorsal photos shown at the bottom of the page. Scutellum and laterobasal ridges typically fully visible. 8-9 well-defined striae per elytron, intervals flattish; humeral shoulders squarish, rounded; lateral margins rounded-elongate; apices weakly rounded, sinuate.

Larvae and pupae: No description as of yet.