Calosoma (Callistenia) subaeneum Chaudoir, 1869
C. subaeneum can be distinguished from C. latipenne with which it has been sometimes confused, by its more elongate body shape and by the elytral sculpture more detectable.
Calosoma (Callistenia) subaeneum subaeneum Chaudoir, 1869
Calosoma subaeneum Chaudoir, 1869: 28 (type material: 1 specimen given by Lorquin, from California); lectotype ♂ designated by Deuve (1978: 250) in Muséum National d'Histoire Naturelle, Paris [examined]
Calosoma (Callisthenes) subaeneum Breuning, 1928: 81
Callisthenes (Callistenia) subaenea Lapouge, 1931: 378
Microcallisthenes (Callistenia) subaeneus Jeannel, 1940: 173
Callisthenes (Microcallisthenes) subaeneus Gidaspow, 1959: 304
Callisthenes (Callistenia) subaeneus Erwin, 2007: 82
Length 17-20 mm. C. subaeneum is characterized by a transverse pronotum with an almost smooth disk and roughness limited to its sides and to the rear part; the posterior lobes of pronotum are broadly rounded not projecting from the base.
On each elytron are clearly visible 15 intervals (triploid type); the striae are indicated by small punctures and on the intervals, although flat, it is possible to recognize shallow transverse wrinkles. The foveae on the primary intervals, in some case, can be quite large.
The color of the upper body, according to the description of the only single specimen seen by Chaudoir, is bright black while the sides and base of the pronotum and the entire surface of the elytra are slightly olive bronze. According to the data provided by Gidaspow there are specimens black with golden luster and others greenish bronze.
C. subaeneum has been described from California and Burgess & Collins (1917: 114) added Idaho and Washington; but Breuning (1928b: 81) and Jeannel (1940: 173) indicated California as the only state where C. subaeneum does exist.
Later, Gidaspow (1959: 305), and more recently Erwin (2007: 82), took up again the indications of Burgess & Collins and as a matter of fact proposed a wider distribution of C. subaeneum from southwestern Canada (British Columbia) up to California, spreading across the States of Idaho and Washington. However, the indication of British Columbia remains very uncertain because it originates from a single vague quote from Venables (1913: 268) taken up by Hatch (1953: 53) but questioned by Bosquet (2012: 251) who reports an opinion of Lindroth (1961: 53).
Examined specimens and literature’s data
United States. California (type, MNHN), Fresno County (Breuning 1928b: 82): Raisin City 70m. (GBIF-CAS); Idaho (Burgess & Collins 1917: 114); Washington (Burgess & Collins 1917: 114): Okanogan County (Winthrop) 950m (www.inaturalist.org).
Notes: Brachypterous. It is preferably nocturnal but can sometimes be observed during the day, having taken refuge in superficial cavities which it digs by itself, according to a behavior common to many carabomorphic Calosoma. The finds of C. subaeneum are scarce, but it seems to have a wider ecological valence than hitherto assumed (Erwin, 2007: 82). It lives in uncovered land or clearings or forest margins, at different altitudes on which the period of activity also depends. In the 1930s the species was collected (GBIF-CAS) in the lowlands of California, on what are now cultivated fields, at an altitude of 70/100m. from February to May. More recently in the State of Washington it was observed (www.inaturalist.org) later in the season, in the month of July, in an artemisia steppe at an altitude of 900/1000 m. Moreover, what has been noted further on, regarding the population of the Big Alkali Lake, would confirm the adaptability of this species.
 Chaudoir, 1869 Californie, ex Musaeo Chaudoir (Typus) (coll. Muséum National d'Histoire Naturelle, Paris) |
 Chaudoir, 1869 (photo: Mackenzie Flight) |
Calosoma (Callistenia) subaeneum dawsoni (Dajoz, 1997)
Callisthenes (Microcallisthenes) dawsoni Dajoz, 1997:70 (type locality: California, Mono county) type material: 19 specimens, no repository given
Callisthenes (Callistenia) dawsoni Erwin, 2007: 76
Length 15-16 mm. An alleged additional new species, Callisthenes (Microcallisthenes) dawsoni Dajoz, 1997, of which have been found less than twenty specimens, has been described by the author in comparison with C. moniliatum, to which it should be similar because of the elongated shape and the color of the upper body, brilliant bronze or dark bronze.
Actually, as can be judged from the original description, it seems more similar to C. subaeneum because of the elongated body shape and the bronze color of the upper body. The more so because, as it happens in C. subaeneum, the elytral sculpture is characterized by striae identified by shallow punctures and by flat intervals, of which the primary ones are with large, metallic blue foveae.
The penis has an apex elongated and the ligula is thin with a bent end, as happens in many species of the subgenus.
In conclusions, in the absence of additional findings, it seems more probable that C. dawsoni is an ecologically well isolated population of C. subaeneum with some little morphological differences as more pronounced color and slightly smaller size.
Examined specimens and literature’s data
United States: California: Mono County, Big Alkali Lake, (road between Mammoth Lake and Benton), 2100 m. (Dajoz, 1997: 70)
Notes: The typical series comes from the Sierra Nevada in California (Mono County). More precisely, the specimens were collected in special ecological conditions, on the shore of Big Alkali Lake, near the road between Mammoth Lake and Benton, at 2100m altitude in August. We do not know other findings..
The taxon was named after Daniel R. Dawson, at the time director of Sierra Nevada Aquatic Research Laboratory, who facilitated the researches and the discovery of the new Calosoma.
 (Dajoz, 1997) Dajoz R. (1997) "Description et biologie d’un Callisthenes nouveau de la Sierra Nevada de Californie (Coleoptera: Carabidae)", Nov. Revue Ent. (N. S.), T. 14, Fasc. 1: 70 |