Calosoma (Chrysostigma) affine Chaudoir, 1843

Length 16-20 mm. C. affine has elongated elytra with almost parallel sides and with sculpture consisting of punctate striae and flat intervals. Respect to C. semilaeve and C. simplex, that have similar body shape and similar elytral sculpture model, C. affine is characterized by the metallic green foveae on the primary intervals that stand out on the elytral surface. Furthermore, the humerus of its elytra is with a strong serration that is more evident than in the other species of the subgenus.
There may be some confusion between C. affine and C. ampliator in the citations of the scientific literature. In fact Breuning (1926b: 174), reviewing the description of Calosoma ampliator by Bates (1891: 223), but apparently without knowing the type, considered it as a synonym of C. affine, followed in this by Jeannel (1940: 169). Later Gidaspow (1959: 267) has re-evaluated as a species C. ampliator, however, as discussed when dealing with C. peregrinator, C. ampliator must be considered as one of the synonyms of the latter species without any relationship with C. affine.
C. affine is present in northern and central Mexico and in southwestern United States, however Bosquet (2012: 239) questions its presence in Missouri (where the type of Calosoma triste should come from) and in Arkansas (Burgess & Collins, 1917: 97).

Examined specimens and literature’s data
Mexico. Mexico (type MNHN); Baixa California: La Paz (Jeannel, 1940: 170); Chihuahua: Santa Barbara, Salaices (Gidaspow, 1959: 269), Casas Grandes (www.inaturalist.org); Durango: Villa Lerdo (= Ciudad Lerdo) (sub C. triste, NMP); Hidalgo: Pachuca (Burgess & Collins, 1917: 97); Mexico DF: Tacubaya (Jeannel, 1940: 169), Villa de Guadalupe (Gidaspow, 1959: 269), Tláhuac, Santa María Ajoloapan (www.inaturalist.org/); Nuevo Leon: Apodaca, Monterrey (Gidaspow, 1959: 269); Oaxaca: Zaachila (Gidaspow, 1959: 269); Tamaulipas: Valle del Maiz (Gidaspow, 1959: 269)
United States. Arizona: Apache County, Yavapai County, Gila County, Pinal County, (Gidaspow, 1959: 269), Pima County, Maricopa County (http://bugguide.net/), Santa Cruz county, Cochise County (UASM), Yuma County (http://madrean.org/); California: Orange County, San Joaquim County, Imperial County (Gidaspow, 1959: 269), Riverside County (http://madrean.org.; www.inaturalist.org/), San Diego County: San Diego (Burgess & Collins, 1917: 97), Mission Trails Regional Park (www.inaturalist.org/); Colorado: Fort Collins (Breuning, 1928a: 110), Denver County, Baca County (Gidaspow, 1959: 269); Kansas: Kearny county (UASM); Sherman County, Reno County, Atchison County, Fort Riley County, Kiowa County (Gidaspow, 1959: 269), Hamilton County (https://bugguide.net/ 1312882); Minnesota: Olmsted co., Martin co. (Truman) (Gandhi & al,, 2005: 922); Nebraska (Gidaspow, 1959: 269), Nevada (Erwin, 2007: 74); New Mexico: Socorro County (https://bugguide.net/), Water Canyon (sub C. triste Snow,1881: 39), Dona Ana County (Gidaspow, 1959: 269), Eddy county (www.inaturalist.org); Oklaoma: Cleveland County (Gidaspow, 1959: 269), Garfield (Erwin, 2007: pl.13), Tillman County (http://madrean.org/); South Dakota: Meade County, Pennington County (www.inaturalist.org); Texas: Presidio county (UASM); El Paso County, Live Oak County, Travis County, Nueces County (http://bugguide.net/), Hidalgo County: Bentsen Rio Grande S.P. (www.inaturalist.org/), Denton County (SB), Taylor County (SB), Brewster County, Brown County, Starr County (Gidaspow, 1959: 269), Bell County: Holland (www.inaturalist.org/), Wise county: Springtown, Bridgeport (www.inaturalist.org/), Stonewall county, Cameron County: South Padre Island (www.inaturalist.org/), Jeff Davis County (TL); Utah: Springdale, Zion NP (www.inaturalist.org/).

Notes: Winged, diurnal and nocturnal, sometime swarming in large number of individuals. It can be found in lowlands and mountains up to 2400m altitude. Adults live on open ground as pastures and tilled fields (Larochelle & Larivière, 2003: 175), they mostly look for prey on the soil and can be caught with pitfall traps. C. affine has been cited as a predator of cutworm (caterpillar of Noctuidae family) that causes damage to cotton (Hake, 1996: 264). It is active in April-May to September-November, according to data of examined material.

Calosoma (Chrysostigma) affine ♀ Chaudoir, 1843 Mexico (type) (Muséum National d'Histoire Naturelle, Paris)

Calosoma (Chrysostigma) affine ♂ Chaudoir, 1843 (syntype of Calosoma triste LeConte, 1844) Nebraska, Kansas, N.Dak, S.Dak, Okla, Colo, Wyo, Mont (Museum of Comparative Zoology, Harvard University, Cambridge, Massachusetts, USA)

Calosoma (Chrysostigma) affine ♂ Chaudoir, 1843 United States: Texas, Denton county, Justin, 25.X.1976, Gaumer and Murray lgt.

Calosoma (Chrysostigma) affine ♀ Chaudoir, 1843 United States: Texas, Taylor county, 26.nov.66, McWorther