Calosoma (Chrysostigma) semilaeve LeConte, 1852

Length 20-27mm. C. semilaeve, as C. affine and C. simplex, has an elytral sculpture with flatten intervals and striae indicated by superficial punctures only. The color in the three species is dull black. C. semilaeve is easily distinguished by the strongly transverse pronotum and by the sculpture of elytra with clearly scaly intervals, especially at the humeri.
It lives in the southwestern United States: Arizona, California, Colorado, Idaho, Nevada, New Mexico, Oregon, Utah, and it is present in the north west of the Baja California peninsula, including Guadalupe island (Mexico).
Some specimens of Calosoma have been found in the Pleistocenic asphalt beds in Rancho La Brea at Los Angeles, California, and have been attributed to C. semilaeve, which is still present in the same area (https://calphotos.berkeley.edu/). These findings would confirm that past climate conditions (between 40,000 and 100,000 years ago) of the Los Angeles region were consistent with, or very similar to, the current Mediterranean climate.
On several occasions C. semilaeve was imported from the United States to Hawaii, as a possible aid in controlling Lepidoptera Noctuidae infestations, but acclimatization always failed. However, it recently happened that a single specimen accidentally imported with loads of vegetables from California was found at the port of arrival on the island of Hawaii (Liebherr et al., 2023).

Examined specimens and literature’s data
Mexico. Baja California: Guadalupe island (Horn, 1876: 199, www.inaturalist.org), La Misión, Ensenada env, Parque Nacional Constitución de 1857, La Rosa de Castilla, Real del Castillo Nuevo, Valle de Guadalupe, Bahia Todos Los Santos, San Pedro Mártir, Tijuana (www.inaturalist.org)
United States. Arizona, Pima County (http://bugguide.net/), Maricopa County, Gila County (http://madrean.org/), Paradise Valley, Huachuca Mountains (www.gbif.org), Santa Cruz County (www.inaturalist.org); California: Alameda co. (syntypes of semilaeve davidsoni and semilaeve adjutor; NMNH), San Josè (Burgess & Collins 1917: 90), Hollywood, Whittier, Compton (Burgess & Collins 1917: 91), Los Angeles co. (SB), La Puente (EM), Orange County (AVT, EM, SB), San Diego County, (http://madrean.org/), Chula Vista, Coronado, Mission Trails Regional Park, Altadena, Algonodes Dunes, Long Beach, San Diego, Tijuana river valley, Riverside county (www.inaturalist.org/), Rancho Bernardo, Lake Hodges, Borrego Springs, (http://www.beetlesofcuyamacamountains.net/), Anza-Borrego Desert State Park (http://anzaborrego.ucnrs.org/), Imperial County (Glamis), Ventura County, Kern County (http://bugguide.net), Wildcat Canyon (www.gbif.org); Colorado: Golden Gate Canyon (www.inaturalist.org); Idaho: Camas co. (Burgess & Collins 1917: 91); Nevada: Carson City (www.inaturalist.org); New Mexico: Ramon, Lincoln county (UASM), Bandelier (www.gbif.org); Oregon (Jeannel, 1940: 169); Utah (Gidaspow, 1959: 271)

Notes: Winged. It is found from lowlands to midlands up to 1300m altitude, on open ground and tilled fields. It is diurnal as well nocturnal and feeds on caterpillars, cutworms (Elateridae larvae) and other ground-inhabiting larvae (Burgess & Collins 1917: 91).
The adults are active starting from February-March with a maximum in April-May but they can be found up to October.
A brief description of larval stages can be found in Burgess & Collins (1917: 92).

Calosoma (Chrysostigma) semilaeve ♂ LeConte, 1852 United States: California, Orange co., Balsa Chico beach, V.1983, Taylor leg. (coll. Vigna Taglianti)

Calosoma (Chrysostigma) semilaeve ♀ LeConte, 1852 United States: California, Los Angeles, Santa Monica mountains, 16.IV.83 Baierl lgt.