Calosoma (Castrida) galapageium Hope, 1838

Calosoma galapageium Hope, 1838: 130 (type locality: "Habitat in insulis Galapageis"); holotype ♂ in British Museum of Natural History, London [examined]
Castrida galapageium Basilewsky, 1968: 204

Length 15-18,5 mm. C. galapageium had long been confused with C. granatense at least till the review of all the populations of the islands of Galapagos Archipelago, made by Basilewsky (1968) .
C. galapageium has rear wings reduced to different degrees but not functional; one specimen having relatively larger wings (53 % of maximal wing development) was in the possession of functional flight muscles; all other specimens showed wing musculature completely absent (Desender & Dijn 1989: 135). The body is elongated with rounded shoulders. The upper body is blackish-brown with a very faint greenish reflection, and the lower body, the antennae, the oral pieces and the legs are of a testaceous color. The sculpture of the elytra is flattened.
The first specimen was found by Darwin, presumably in the central part of one of the islands of the Galápagos Archipelago. A few more specimens were later found in grasslands of the high ground terminal of Santiago Island (Van Dyke, 1953: 11) from which most probably also comes the specimen captured by Darwin (Basilewsky, 1968: 204).
Apparently C. galapageium represents an initial stage of the regressive trend (reduction of the wings, attenuation of pigments, flattening of the sculpture of the elytra) common to the species typical of the environment of the high ground terminal to the islands Galapagos.
Until a few years ago only four old specimens of C. galapageium were known (Basilewsky, 1968: 204). However in subsequent years targeted research has made it possible to find a few dozen specimens on which to conduct more in-depth studies (Desender & Dijn 1989: 135).
C. galapageium has been only found at the top of island Santiago (James) at around 800-900 m.

Examined specimens and literature’s data
Galápagos Archipelago (Ecuador). Galápagos (holotype, BMNH); Santiago (James Island): sommet de l’île (Basilewsky, 1968: 204); Sommet Santiago, 900m (IRScNB)

Notes. Brachypterous, wings not reaching the half of an elytron. It is predator on ground dwelling invertebrates. It is restricted to open grassy meadows in the higher parts of the island, and it is especially abundant at the summit. The ancient catches were made at the beginning of the rainy season, between the end of December and the beginning of January (Basilewsky, 1968: 204). According to more recent data (Peck, 2006: 106) the species should be active in March - May and October - December.

Calosoma (Castrida) galapageium
Hope, 1838
Ecuador, Galápagos, Darwin lgt. (Typus)
(British Museum of Natural History, London) (photo V. Volpe)
updated April 23 2020