Size: 7-9.4mm

Seasonality: On the West Coast: Late March-October

Distribution; Across North America and the West Indies, excl. Baja California Sur

Information:  In BC, WA, OR, CA, Agonum decorum (the green glabrous form of decorum described by Dejean as A.californicum which is more common than the red form in these areas) can be found on or under plant debri incl. logs, stones,  near water.   Populations within rainforests tend to have fully developed flight wings, but do not often use them during the day, but may be seen flying to mercury vapour and UV light traps.  The species overwinters under loose bark, stones, leaf litter, or in small burrows along shorelines.         

Body colouration is highly variable per location, with the most common morph being the green or black head, red leg-red pronotum, black or blue elytra morph, which is not common on the West Coast, though can be found in some areas in California, and east Oregon/Washington. On the West Coast and part of Arizona, the most common colour morphs are the lustrous, fully grey-black morph and the green lustrous morph, both formerly recognised as Agonum californicum Dejean.  Also in Arizona and Northern Mexico one may find fully iridescent green and fully iridescent blue A.decorum morphs.

Description: Certain aspects of Agonum decorum vary between each morph. Listed below are comparisons of the two morphs found on the North American West Coast.

Green-Glabrous Morph-

Body: Elongate-quadrate, slender. Elytra: eight well-defined striae. Very few setae on each elytron, a few small setae may be found along the lateral elytral margins. Antennal pubescence begins on the second antennomere following the pedicel. Legs dark red to black. Humeral shoulders of elytra broad, body shape excluding head and pronotum nearly quadrate. Pronotum bronze or green-black, elytra silvery-black or greenish-black. Head glossy dark blue-green or black, palpi dark red, mandibles dark red, scapus red.

Red Morph-

Body: Elongate-quadrate, ovate, slender. Elytra: eight well-defined striae on each elytron; many small, golden setae scattered across elytra. Antennal pubescence begins on the first antennomere following the pedicel. Legs pale orange. Humeral shoulder width of elytra relatively narrow, body shape excluding head and pronotum narrowly ovate. Pronotum pale or dark orange, elytra glossy black or dark matte blue. Head glossy dark blue-green or black, palpi dark red, mandibles dark red, scapus red.