Calosoma (Callitropa) palmeri Horn, 1876

Length 18-22 mm. palmeri is a small, brachipterous species, entirely shiny black, for which Breuning (1927) had created the subgenus Paracalosoma. It has a posteriorly narrowed pronotum, oval elytra, widened at the rear, with very superficial striae.
It is found only on Isla Guadalupe, a large island that belongs to the Baixa California, about 270 km from the coast, but Erwin (2007: 99) reported a single capture on the Benito del Oeste island in the San Benito archipelago, much more close to the coast.

Examined specimens and literature’s data
Mexico. Baja California: Guadalupe (AMNH, MNHN, NMB), southern part of the island 430m (www.inaturalist.org), Campamento de Cooperativa Agropecuaria "Francisco Javier Maytorena” 1200m (www.inaturalist.org), Guadalupe, summit of the island 2500ft (AMNH)

Notes: Brachypterous. Lives on lowland and midlands up to the top of the island at 750/1200m. Adult active individuals have been found in January and March, in the period in which most rainfall occurs. but they can remain active until June, at higher altitudes.
The species is named after Edward Palmer (1829–1911), a self-taught botanist and archaeologist. Palmer, British-born but soon emigrated to America, collected natural specimens in the southwestern United States, Florida, Mexico (including Baja California), and South America, for the Smithsonian and many other Institutions.

Calosoma (Callitropa) palmeri ♂ Horn, 1876 Mexico Guad(alupe) Is(land) (syntype) (coll. and photo: Museum of Comparative Zoology, Harvard University, Cambridge, Massachusetts, USA)

Calosoma (Callitropa) palmeri ♀ Horn, 1876 California, Is. Guadalupe (coll. Naturhistorischen Museum Basel)

Calosoma (Callitropa) palmeri ♂ Horn, 1876 Guadalupe, summit 2500ft, 2.III.1911 (coll. American Museum of Natural History, New York)

Calosoma (Callitropa) palmeri ♀ Horn, 1876 Southern California, Guadalupe (coll. American Museum of Natural History, New York)