Biological notes

Calosoma sycophanta, from Curtis, British Entomology, 1823-1840: plate 330 The adults of most of species of Calosoma are winged and in some cases, they fly very well. Even Darwin has reported in his Journal a Calosoma that flew on board 10 miles off the shores of northern Patagonia (possibly just that specimen later described by Hope as Calosoma patagoniense = C. retusum). In that occasion Darwin (1845: 185) noted the ability of these beetles to fly long distances, which he considered most remarkable, since the majority of Carabidae rarely or never take wing. In addition, it is enough to recall the cases of Calosoma (Campalita) algiricum and Calosoma (Caminara) olivieri, that living in northern Africa and the Middle East, occasionally travel long distance up to the opposite coast of Europe, presumably aided by winds and currents of air.

Calosoma (Orinodromus) gestroi refugee under water The winged species are active during the day or at night or both. Sometime the artificial lights attract them in huge quantities. Usually they feed on larvae of Lepidoptera that hunt on trees or shrubs, or on the ground. The active period of adults is therefore linked to that of the prey. In case of major infestations of caterpillars, or larvae of other insects, adults of some species of Calosoma have been noted to appear suddenly in large numbers. The mechanism that synchronizes the activity of Calosoma beetles with periods of massive presence of caterpillars is not yet fully known and various assumptions have been made. For some, the remarkable mobility that characterizes winged Calosoma might perhaps be sufficient explanation for these sudden concentrations of individuals (Battiston & Biondi, 2015: 11). On the other end it has also been observed that Calosoma fertility tends to shrink when prey is scarce (Weseloh, 1985) while the number of predator larvae increases during caterpillar infestations (Kamata & Igarashi, 1995). Finally, additional factors able to influence their respective life cycles were investigated as the small increases in soil surface temperature caused by the defoliation due to caterpillars that could stimulate the adults Calosoma to leave their underground burrows earlier and begin foraging (Jacobs & al. 2011: 641).
Other species and various subgenera of Calosoma have short wings, unfit to fly, or do not have wings at all (more exactly, the wings are reduced to nearly invisible stumps) . For convergent evolution, such subgenera remind the appearance and the way of life of Carabus. They are therefore adapted to live on the ground and during the periods of inactivity, they take refuge under vegetation, under stones or in small hollows that they prepare for themselves. Important groups of species, that have these characters, are gathered in the Palearctic subgenus Callisthenes, mostly living in Central Asia, and in the Nearctic subgenus Callistenia, spread along the chain of the Rocky Mountains. The species of these two subgenera are mainly linked to the environment of desertic or steppic highlands of medium height but in some case they go up to a height of 3000-3500 m.
In the Mexican Sierras, mainly around a height of 3000 m, we meet other highly modified species of Calosoma, that were included in the subgenera Carabomimus and Calopachys, they are of reduced size and wingless, and also superficially reminiscent the appearance of the genus Carabus.
Likewise, in Africa, along the mountains bordering the Rift Valley, from 2000 m up to high altitude pastures around 3500 4000 m there are other specialized subgenera adapted to life under stones: Carabops, Carabophanus, Carabomorphus, and Orinodromus.
In South America, adaptation to life on the ground by species of the subgenus Castrida has not resulted in such profound changes. C. bridgesi, which lives in Andean high desert vegetation up to 3500 m, has some characters of convergence with the other Carabus-like Calosoma, including the small size and the loss of the ability to fly because of reduced, non-functional, wings. Equally modified, although the altitude in which they live is restricted to around 550-650 m, are the three species of the Galápagos Archipelago (C. leleoporum, C. galapageium, C. linelli) found in the humid environment of the high ground terminal of three different islands. C. linelli that is the most advanced one, has the wings completely atrophied, it is very small (12-13 mm) and presents an appreciable depigmentation. However all these species, despite the morphological effects of adaptation to habitat specific conditions, maintain many characters that do not allow for separating them from the other winged species of the subgenus Castrida.
Lastly, we would like to note that the peculiar conditions of the alpine habitat and the morphological specialization do not always are correlated as in the cases mentioned above. Some populations of C. maderae indicum are exclusively found at higher altitudes meadows in the Himalaya (up to 4000 m), under stones where they are often associated with Tenebrionidae. Despite the extreme environmental conditions and such a peculiar a way of life, the individual of these populations are winged and although smaller, are externally little different from the ones that live in a more ordinary way at lower altitude. The little morphological differentiation seems to indicate that in this case the ecological isolation is probably not too old and still poorly effective.