Size: 7-8.3mm

Seasonality: April-October

Distribution; BC, WA, OR, n. CA, w. ID

Information:  This small Anchomenus species is generally found in relations to streams, creeks, ditches, and the like, as well as ponds, river banks, and wetland areas. A.quadratus tend to overwinter nearby the body of water beside which they spend the majority of the year; generally huddled together in groups under rocks or logs overwinter.     

Description: Body: elytra glossy black or black with green lustre, pronotum black, sometimes with faint blue lustre.  Pronotum loosely quadrate, hind angles obtuse, but sharp, never acute, pronotal margins have slight lip, margins rounded, broadest near marginal midpoint, width of pronotum should be about the same at the apex and the basal region. First three antennal segments have only one of two long setae protruding from them, the rest are coating in a fine layer of pale setae. One seta on each scape, longer than all others found on the antennae. Pronotal disk covered in numerous small wrinkles, spreading away from the median line.  Shallow pits, riddled with many small, uneven structures, are present, one beside each of the hind pronotal angles.    Tips of elytra (tip of apical region) abruptly sinuate lateral margins of the elytra near their apices, the tip of each elytron is neither flat, nor sharply pointed, rather they are more rounded.       Underside, including all limbs and appendages are black.

Larvae shown below.