Calosoma (Castrida) galapageium Hope, 1838

Calosoma galapageium Hope, 1838: 130 (type: "Habitat in insulis Galapageis"; British Museum of Natural History, London)
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 wings very reduced, not reaching the half of elytron the body is elongated with rounded shoulders. The upper body is blackish-brown with a very faint greenish reflection, and the under body, antennae, oral pieces and legs are testaceous. The sculpture of the eytra 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 one intermediate 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 some other few catches were added.
C. galapageium has been only found at the top of island Santiago (James) at around 800-900 m.

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

Notes: Brachypterous, restricted to open grassy meadows. 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)

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