Size: 7.5-9.1mm

Seasonality: February-July and October to mid-December, varies per region.

Distribution; BC, AB, WA, OR, CA, ID, MT, West NV, UT, AZ, NM, MX-SO, MX-BN, most of the islands off the coast of California and Baja California Norte.

Information: may be found under pieces of bark on the ground, under rocks, among leaf litter, and under debri along coastal beaches. Because they are a primarily nocturnal carabid species, they may be abundantly found wandering at night on beaches, along streams; oak and coniferous forests along with more urban settings such as backyards, as well as along the beaches of the West Coast.

Description: body: elongate-ovate, moderatley robust, flattish. Head triangular, without any facial sculpturing: surface of the head smooth. Two supraorbital setae over each eye. Eyes rather close the head, not bulging laterally, angled forward slightly. Clypeus with two small setigerous pits, near either lateral margin. Labrum slightly longer than the clypeus, rectangular. Mandibles mostly straight, slightly curved at the tips. Palpi pale orange. Antennae pale orange, pedicel just over half the length of the scapus; antennal pubescence begins on the second half of the second antennomere following the pedicel. Head dark or pale red in colour. Pronotum dark or relatively pale red in colour, lateral margins often slightly paler, weakly opaque reddish-orange. Pronotal disk squarish; front margin very weakly rounded inward; front angles obtuse, nearly squared; pronotal disk weakly convex; lateral margins rounded, sloping forward; hind angles rounded-obtuse. No beading on the pronotal margins. Median line weak, nearly vanished: strong on subspecies granicollis. Disk mostly smooth, but somewhat rough along the base. The pronotal base of C.r.ruficollis often partially obscures the laterobasal ridge of the elytra. 8 shallow striae per elytron, intervals flat. Elytra elongate-ovate; lateral margins rounded-elongate; apices pointed, somewhat rounded. Elytra matte to semi-glossy black. Ventral colouration glossy to semi-glossy black, legs orange-yellow.

Three subspecies in North America: Calathus ruficollis grandicollis, Calathus ruficollis ignicollis, Calathus ruficollis ruficollis.