Head: Reddish-bronze. Mandibles and whiskers (palpi) reddish-orange.
Antenna: Brown, long; extending to middle of wings. First 3 segments pale yellowish-brown. Segment 3 and 4 are equal in length.
Thorax (Pronotum): Reddish-bronze; squarish with pale pile; rounded sides. Faint indented line running down middle. Lower thorax has an indented depression each side of center.
Wings (Elytra): Dull blue-purple brown to slightly greenish, not metallic. About 8 indented lines running from base to wing tip. Center of base area (scutellum) black, V-shaped. Wings covered with very short, thick yellowish pile.
Legs: Thighs (femora) reddish-orange. Shins (tibiae) pale yellow. Feet more brownish-yellow. Male front feet wider with 3 large pads on underside.
Similar Species: Chlaenius aestivus has antenna segment 3 much longer than 4, thorax more squarish at lower margin. C. nemoralis has metallic green head and thorax, not reddish. Trichotichnus dichrous almost identical, but red on head and thorax although shiny, is not metallic or brassy-looking.
Size: 12 to 13 mm.
Habitat: Deciduous forest edges, wet meadows and creek edges, especially with long grasses and sedges.
Food: Snails, slugs, moth and beetle larvae.
Flight Time: May and again in August.
Life Cycle: Females lay eggs in mud cells formed on the undersides of grass leaves, especially sedges, eggs becoming adults in late summer. Adults over-winter. One generation per year. This beetle emits a foul, manure odor when disturbed. Attracted to lights.
In 2015, Douglas discovered Neonicotinoid insecticide would kill 60% of Chlaenius tricolor if they ingested slugs contaminated with the insecticide.
Comments: Essex County – Point Pelee National Park, Lake Erie Islands and Ojibway Prairies. Kent County – Rondeau Provincial Park.
For information on synonyms, references and type specimens see next page