Calosoma (Chrysostigma) obsoletum Say, 1823

Length 17-25mm. C. obsoletum has pronotum distinctly and evenly punctate with rounded rear lobes, just protruding from the base The elytra relatively longer with almost flat but still recognizable sculpture. All the intervals are a little convex and scaly. The foveae on the primary ones are not wider than the intervals themselves. The color of upper body is black, non-metallic.
C. obsoletum is present in the western United States and in the south-west of Canada.

Examined specimens and literature’s data
Canada. Alberta: Medicine Hat, Cypress Hills, Lethbridge, Welling, Chin lake, Rosebund, Morrin, Hanna (Lindroth, 1961: 50), Empress (UASM), Irvine (https://bugguide.net/); Manitoba: Brandon, Souris, Beresford, Hayfield, Treesbank (Lindroth, 1961: 50); Saskatchewan: Great Deer, Lemberg, Saskaloon, Swift Current (Lindroth, 1961: 50)
United States. Colorado: Denver county (UASM); Kansas: Wallace county (Jeannel, 1940: 108), Atchison (SB), Thomas County (http://madrean.org/), Colby (www.gbif.org); Minnesota: Olmsted co., Cass co. (Cass lake), Rock co. (Luverne), Big Stone co. (Odessa), Polk co., Mille Lake co., Ramsey co., Beltrami co., Kittson co. (Halloch), Nobles co., Pipestone co., Lincoln co., (Gandhi & al,, 2005: 922); Nebraska: Friend (Burgess & Collins, 1917: 89), Custer County (EM), Mitchell (EM); Nevada: Elko co. (La Rivers, 1946: 136); New Mexico: Fort Wingate (syntype of obsoleta microsticta, NMNH), Maxwell, slopes of Eagle Tail Mountain (Burgess & Collins, 1917: 88), Water Canyon (Snow, 1881: 39), McKinley county (UASM), Colfax County (http://madrean.org/) 17 km SW/S Bernardo, Bandelier (www.gbif.org); Texas: Carson County (http://madrean.org/), Jeff Davis Co., Panhandle (www.gbif.org); Utah: Jensen (www.inaturalist.org); Wyoming: Riverton, Jellowstone Park (Jeannel, 1940: 108).

Notes: Winged. It is found from lowlands to uplands, up to 2100m altitude, on praries, open ground, tilled fields. It is crepuscular as well nocturnal and some time attracted to light at night, taking refuge under stones and various shelters in daytime. Adult feed prefereably on caterpillars of the moth Hemileuca oliviae and the larvae on the pupa of the same species (Burgess & Collins 1917: 87). Adults individuals have been found active from April to November, and overwintering in small cavities in the ground.
A brief description of larval stages can be found in Burgess & Collins (1917: 89).
It remains to add a curious detail, a consequence of the hasty descriptions in vogue in the nineteenth century and of the communication difficulties of the time. In 1826 Dejean described, a specimen sent to him by Say with the name C. luxatum, preserving the name given by the donor. Later LeConte realized that the specimen in question was actually a specimen that Say had named Calosoma indistictum without describing it and he added a short description of it (LeConte, 1845: 208). However Say (1823: 149) had described with the name C. obsoletum still the same species of which he had sent the specimen to Dejean and had used the name luxatum for another species (Say, 1823: 149). Consequently the name C. luxatum used by Dejean (1926: 196), beside being homonym with C. luxatum Say 1823, is a junior synonym of C. obsoletum Say 1823, of which C. indistictum, under the involuntary authorship of LeConte, became also a synonim.

Calosoma (Chrysostigma) obsoletum ♂ Say, 1823 United States: Texas, Denton county, United States: Kansas, Atchinson, City streets, at light; JW McReynolds; May, 18, 56

Calosoma (Chrysostigma) obsoletum ♀ Say, 1823 United States: Kansas, Atchinson, City streets, at light; JW McReynolds; May, 12, 56