Calosoma (Castrida) granatense Géhin, 1885

Length 14-23 mm. Nouvelle-Grenade, as it is indicated in the original description of C. granatense, is the ancient name (from the 16th to the 19th century) of the region approximately corresponding to the present states of Colombia, Panama, Venezuela and Ecuador. Breuning (1927: 202), that believed C. granatense synonymous with C. galapageium previously described from the Galapagos archipelago, supposed that it was also present in the opposite South American coastal areas: in Colombia, basing on two quotations from Gehin (1885: 59) and Roeske (1900a: 59), and in Peru, Callao, having seen specimens from there in the Berlin museum.
However, these last indications have never been confirmed and they seem very unlikely. Actually C. granatense, which is distinct from C. galapageium, is only present in Ecuador, limited to the islands of the Galapagos archipelago where it is the most common species and possibly very near to the one from which the others evolved.
C. granatense, as all the other endemic species of the Archipelago, has the elytral margin smooth, without trace of serration. The color of its upper body is metallic bluish green. In an high percentage of specimens, the basal seta of the pronotum is lacking. The metaepisternum is quite smooth with some scattered large punctures.
Jeannel (1940) has considered C. granatense in the subgenus Microcalosoma, previously created by Breuning (1927: 123) for C. linelli, another species of the same Archipelago, but the subgenus has been considered superfluous by Gidaspow (1953), followed in this by Basilewsky (1968) and all the later authors.
C. granatense exists in almost all the islands of the Archipelago, (Archipiélago de Colón): Baltra (South Seymour); Darwin (Culpepper); Eden; Española (Hood); Fernandina (Narborough); Floreana (Charles), including Gardner Islet; Genovesa (Tower); Isabela (Abemarle); Marchena (Blindoe); Pinta (Abingdon); Pinzón (Duncan); Rábida (Jervis); San Cristobal (Chatham) including Pitt Islet; Santa Cruz (Indefatigable ); Santa Fe (Barrington); Santiago (San Salvador, James); Seymour; Wolf (Wenman).
C. granatense is widespread at low altitude but it is also present, although more rare, at altitudes up to 500m, on Floreana and on the vulcanoes of Isabela. These altitude populations may present some cases of polymorphism and they may include some individuals with reduced wings. However, in the heights of the oldest islands, namely San Cristobal, Santiago and Santa Cruz, we find other populations, pertaining to three distinct species (C. linelli, C. galapageium and C. leleoporum ), which surely have ancestors in common with C. granatense but that are altogether brachypterous and variously adapted as ground dwellers.
In this regard it should be noted that, because of their capability to react to the selection pressure, the Calosoma of Galápagos Archipelago were the subject of several studies on population genetic structure and differentiation (Desender et Al, 1989, Desender et Al, 1991, Desender et Al, 1998, Dhuyvetter et Al, 2002, Hendrickx et Al, 2015).
It follows from these studies that the populations of the different islands have a relatively high genetic differentiation and therefore long-distance dispersal would seem rather rare. Conversely gene flow within populations of the same island tends to remain high. Therefore phenomena of speciation have been only possible in the most ancient islands, although the genetic isolation is not always perfect and were observed phenomena of introgression.
In the the more recently formed islands, this constant genetic flow has not allowed the morphological differentiation. However Basilewsky (1968) considered two of these populations as valid subspecies: darwinia Van Dyke 1953, localized in the south east of Isabela island, at medium altitude, and floreana Basilewsky 1968, described from Floreana Island, where it is the only occupant. These taxonomic distintions appear unsustainable both from the genetic point of view as well as from the morphological one. However it must be noted that in the south east of Isabela island, on the slopes of Volcano Cerro Azul, the population of the intermediate humid zones (darwinia) is characterized by a higher percentage of individuals with partial reduction of the wings, probably linked to a lower selection pressure (Desender et Al, 1991 cited by Erwin 2007: 95).

Examined specimens and literature’s data
Galápagos Archipelago (Ecuador). Baltra (South Seymour) (Basilewsky, 1968: 194), Aeropuerto Seymour (www.inaturalist.org); Darwin (Isla Darwin) (Basilewsky, 1968: 197); Eden (Basilewsky, 1968: 196); Española (Hood) (Basilewsky, 1968: 194); Fernandina (Desender & Dijn 1989: 135); Floreana: Las Cuevas bay (sub C. granatense floreana; AVT), Black Beach (sub. C. granatense floreana, NMB), 2km N Asilo de la Paz (www.inaturalist.org); Gardner (Peck, 2006: 106), Puerto Velazco Ibarra (www.inaturalist.org); Genovesa (Tower): Darwin bay (Basilewsky, 1968: 197); Isabela (Abemarle): Banks bay, Tagos Cove, Cerro Alcedo (Basilewsky, 1968: 197), Near Villamil 1300ft. (C. granatense darwinia, typ. loc. Basilewsky, 1968: 198), Isabela (sub C. granatense darwinia, AVT, NMP), Isabela alt. 1300ft (sub. C. granatense darwinia, NMB), Santo Tomás, Sierra Negra 180-490m (Moret, 1986: 92), Sierra Negra 490m, Puerto Villamil (www.inaturalist.org), Urbina bay (sub. galapageium www.joelsartore.com), Volcan Cerro Azul, Volcan Darwin, Volcan Wolf (Desender & Dijn 1989: 135); Marchena (Desender & Dijn 1989: 135); Pinta (Basilewsky, 1968: 197); Pinzón (Duncan): Summit and upper Caldera area (Basilewsky, 1968: 196); Rábida (Jervis) (Peck, 2006: 106); San Cristobal (Chatam): March bay (Basilewsky, 1968: 194), Puerto Baquerizo Moreno, Mirador La Soledad (www.inaturalist.org), Pitt Islet (Desender & Dijn 1989: 135); Santa Cruz: Academy bay (EM, SB), Puerto Ayore (AC, EM, SB), Reserva de los Galapagos, 200m (Moret, 1986: 92), Horneman Farm, Comway bay (Basilewsky, 1968: 196), El Pontudo 450 m, Tortuga Bay, Isla Plaza (www.inaturalist.org); Santa Fé (Barrington) (Basilewsky, 1968: 196); Santiago (James) (Basilewsky, 1968: 197); Seymour (North Seymour) (Desender & Dijn 1989: 135); Wolf (Wenman) (Peck, 2006: 106).

Notes: C. granatense has rear wings variable in size and shape according to the population: lowland populations mostly possess completely developed wings and are able to fly, whereas highland populations show flight wing polymorphism with wing reduction to different degrees (Desender & Dijn 1989: 133).
C. granatense is diurnal and nocturnal, easily attracted to light at night in rainy season and it has been captured by pitfall and malaise traps. It preferably inhabits arid areas of dry vegetation at lower elevations, including tilled fields, where feeds on eggs and larvae of Lepidoptera.
Adults were encountered in activity mostly during the warmer and more humid season in the months from December to May (Basilewsky, 1968), except some populations of zones at medium altitude on Santa Cruz and Isabela island the adults of which were found active in September, with cloudy weather and drizzle (Moret, 1986: 92). Anyway, considering the different habitats where C. granatense fits, likely it can be found active during most of the year (Peck, 2006: 106).
The larva was described by Busato, Desender & Giachino (2001).

Calosoma (Castrida) granatense ♀ Géhin, 1885 Amérique mer., N.vlle Grenade (Typus) (coll. Muséum National d'Histoire Naturelle, Paris)

Calosoma (Castrida) granatense ♂ Géhin, 1885 Ecuador, Galapagos is., Santa Cruz

Calosoma (Castrida) granatense ♀ Géhin, 1885 Ecuador, Galapagos is., Santa Cruz, VII.65, Angermayer lg

Calosoma (Castrida) granatense ♂ Géhin, 1885 Ecuador, Galapagos is., Isabela, 19.VI.1985,Onore lg. (sub Castrida granatense darwinia Van Dyke) (coll Vigna Taglianti)

Calosoma (Castrida) granatense ♀ Géhin, 1885 Ecuador, Galapagos is., Floreana, Las Cuevas Bay, 29.VI.2001, R. Argano lg. (sub Castrida granatense floreana Basilewsky) (coll Vigna Taglianti)