Calosoma (Chrysostigma) calidum (Fabricius, 1775)

Length 17-30 mm. C. calidum is characterized by a sculpture of elytra of homodynamic type in which the intervals are of the same height and width, with dotted striae and intervals interrupted by shallow, transverse wrinkles.
The pronotum is slightly narrowed to the base with broad rear lobes. The color of the upper body is greenish brown, on which stand out large foveae with a cupric bottom, in correspondence with the primary intervals but that generally cover at least part of the adjacent ones.
C. calidum is a relatively variable species and this explains why after the many synonyms discussed by Breuning (1927) and accepted by Jeannel (1940), Gidaspow (1959) has re-evaluated as good species Calosoma (Chrysostigma) concreta, which however, has not been considered valid by later authors.
As for C. lepidum, it has been considered synonymous with C. calidum by Breuning (1928: 84) and Jeannel (1940: 164), but re-evaluated by Gidaspow (1959: 264) as a good species, followed by the subsequent authors. C. lepidum should have shorter elytra, and its pronotum should be a little narrower at the base with small rear lobes, anyway C. lepidum can be easily spotted by its steadily smaller size (17 - 19mm), and by the color of the upper body reddish-brown, with small foveae with green bottom. The penis is the same than C. calidum, but Gidaspow point out that its inner armature is more slender. The wings are normally formed but, by emphasizing some peculiarities of their structure, Lindroth (1961: 51) expresses doubts about its ability to fly, unlike C. calidum which he considers a good flier. However, we think that such morphological differences as the ones we described, by their nature, may also be due to individual variability, possibly influenced by climatic conditions at the time of the various stages of development. The two forms coexist in the northern part of the distribution area, and bearing in mind the variability of characters of the species of Calosoma, it seems preferable to follow the more conservative position taken by Breuning and Jeannel.
As for C. mexicanum, Breuning (1928: 86), without knowing the type, but on the basis of the description and of the figure given by Géhin (1885: 67, note 72, plate IX), considered it as a subspecies of C morrisoni. Jeannel (1940:165) and all the more recent authors followed this opinion. The type examination in MNHN, however, easily allows for recognizing a specimen of C. calidum, albeit somewhat aberrant and with incorrect locality data. Doubt remains about the specimens of Calosoma coming from Nevada that Breuning in the same occasion identified as C. morrisoni mexicanum. These specimens, characterized by raised intervals and large, greenish primary foveae ("the size of the ones of C. calidum"), could perhaps to be themselves specimens of C. calidum.
Finally, Lapouge (1930: 43) thought he could recognize two specimens in the collection of Fabricius existing at the Natural History Museum of London as the types of C. calidum. Since, in his opinion, these specimens belonged to the species later described as C. rugosum (at present = C. chlorostictum), the name calidum should have prevailed for this last species and would not have been usable for the American one, where it should have been replaced by lepidum. However Jeannel (1940: 101) and, more at length, Lindroth (1961: 50) rejected this interpretation and reestablished the nomenclature we use today.
C. calidum, spreads through southern Canada and northern United States, rarely it is found in the southern States and it is absent in the south-western ones. Erwin (2007: 75) cites C. calidum also from Puerto Rico. Furthermore C. calidum is one of the species whose acclimatization in Hawaii was unsuccessfully attempted in the first half of the last century (Liebherr et al., 2023).
A recent publication (Yahiro & al., 2018) reports the discovery on the island of Honshu in Japan of a fossilized elytron of a Carabid that the authors have interpreted (albeit with all the precautions that are necessary in these cases) as possible remains of a Calosoma closely related to Calosoma calidum. The finding occurred in Late Pliocene strata dating back approximately to 2.6 million years ago. Therefore some Calosoma of the calidum group could have been present in Japan in relatively recent times and would have coexisted with other Carabini and with at least one other species of Calosoma (C. inquisitor) whose remains have been found in the same strata and that is still living in Japan.

Examined specimens and literature’s data
Canada. Alberta: Coaldale (sub lepidum, EM), Medicine Hat (sub lepidum, AMNH, SB), Calgary, Brooks, Tilley (sub lepidum, Gidaspow, 1959: 285), Banff National Park, Ralston, Calgary, Onefour, Ranchville, Suffield (sub lepidum, UASM), Calahoo, Edmonton, Slave Lake, Castor, Leduc, Blackfalds, Mundare, Brooks, Chisholm, Ellerslie, Morinville, Cypress Hills, Medicine Hat, Athabasca, Morinville Robinson (UASM), Hilda, Tilley, Brooks, Coaldale, Lethbridge, Monarch, Retlaw, Calgary (sub lepidum, Lindroth, 1961: 51), Edmonton, Duchess, Elk Island National Park, Wainwrait Dunes (www.inaturalist.org), Vulcan County, Onefour (sub lepidum, www.inaturalist.org); British Colombia: Rolla, North Pine, Fort St John (Lindroth, 1961: 51); Manitoba: Virden (SB), Aweme (sub lepidum, Gidaspow, 1959: 285), Glenboro (sub lepidum, Lindroth, 1961: 51), Alexander, Winefred Lake, Richer, Birds Hill Provincial Park, Morden (UASM), Kamloops (www.inaturalist.org), Clear lake, Riding Mountain N.P. (Lindroth, 1961: 51), Hartney, Pine River, Cypress River, Lac du Bonnet, Lockport, Winnipeg (www.inaturalist.org); New Brunswick (Webster, 2016: 392); Newfoundland (the quote by Jeannel, 1940: 164, is believed incorrect by Lindroth, 1961: 50, note 1); Northwest Territories: Norman Wells (Lindroth, 1961: 51); Nova Scotia: Cape Breton Island (Lindroth, 1961: 51), Sable IslandSable Island (www.inaturalist.org/obs/8650220); Ontario: Nipigon, Attawapiskat (Lindroth, 1961: 51), Nipissing (www.gbif.org) , Algoma District (http://bugguide.net/), Flamborough (http://entomocollection.blogspot.it/), Wellington, Erin, Prince Edward Island, St Ignace Island, Kawartha Lakes, Falconbridge, Norwich, Smiths Falls, Perth (www.inaturalist.org/); Québec: Mont-Laurier (SB), Parc National de la pointe-Taillon, St-Raymond (https://bugguide.net/), San Jean de Matha (SB, TL), Charlesbourg (http://entomocollection.blogspot.it/), Trois-Rivières, Baie-Saint-Paul, Clarendon (www.inaturalist.org); Saskatchewan: Foam Lake, Manitou Beach, Beaver Creek, Casa Rio (www.inaturalist.org), Consul (sub lepidum, www.inaturalist.org), Pike Lake (SB), Usborne, Maidstone (www.inaturalist.org), Tisdale, Whitefox (Lindroth, 1961: 51), Prud'homme (sub lepidum, UASM), Great Deer, Craven, Richmond, Bounty, Eagle Hill Creek, Saskatoon (sub lepidum, Lindroth, 1961: 51), Baie-Saint-Paul, Lake Winnipeg, Mankota (sub lepidum, https://bugguide.net).
Saint Pierre et Miquelon (France) (Jeannel, 1940: 164) (Lindroth, 1961: 47 note 1)
United States. Colorado: Boulder County, Larimer County (www.inaturalist.org), Denver (Breuning, 1928: 86); Connecticut, Delaware, District of Columbia, Georgia (Burgess & Collins, 1917: 98); Illinois: Chicago (SB), West Marion Precinct (www.gbif.org); Indiana: Newton County (www.inaturalist.org); Iowa: Keokuk (syntype calida expansa, NMNH) Pottawattamie County (http://bugguide.net/), Sioux City (www.inaturalist.org/); Kansas: Topeka, Riley co. (sub concreta; Gidaspow, 1959: 266), Elmendaro (www.gbif.org), Lyon County (www.inaturalist.org); Kentucky (Burgess & Collins, 1917: 98): Metcalfe County (TL); Maine: Hope (www.gbif.org), Somerset County, Cumberland County (www.inaturalist.org); Maryland: Plummers island (Erwin, 2007: 75); Massachusset: Worcester County, Nantucket, Tuckernuck island (www.inaturalist.org/); Michigan: Washtenaw co. (EM), Ontonagon County, Boyne City, Elmira, Oscoda County, Emmet County (www.inaturalist.org/); Minnesota: St. Louis County (http://bugguide.net/), Cass County, Beltrami county, Scott county (www.inaturalist.org/), Washington County (www.gettyimages.it/); Missouri (syntype calidum var. lepidum, MCZ), Saint Joseph (sub concreta; Gidaspow, 1959: 266), Scott County (www.inaturalist.org); Montana: Bearpaw, Havre (=Harve), Helena, Dutton (sub lepidum, Gidaspow, 1959: 265), Carbon County (http://bugguide.net/1528879), Phillips County, Valley County, Wheatland County (sub lepidum, www.inaturalist.org); Nebraska: Rock County, Dawes County, Sioux County (www.inaturalist.org); Nevada: Las Vegas (syntype calida laticollis, MCZ), Hiko range (Breuning 1928a: 87, sub morrisoni mexicanum); New Hampshire, New Jersey (Burgess & Collins, 1917: 98); New Mexico: Jemez Springs, Valles Caldera (www.inaturalist.org); New York: Ithaca (UASM); North Carolina (Burgess & Collins, 1917: 98); North Dakota: Cass county, Fargo, Hettinger county, Dunn county (UASM), Sheridan co., Stutsman co (www.inaturalist.org); Ohio (Burgess & Collins, 1917: 98): Lake County (www.inaturalist.org); Oregon (Bousquet, 2012. 240); Pennsylvania (Burgess & Collins, 1917: 98); Rhode Island (Bousquet, 2012. 240): Nantucket (www.inaturalist.org); South Dakota: Meade County, Custer County, Clay County (www.inaturalist.org); Tennessy (Burgess & Collins, 1917: 98); Utah (Bousquet, 2012. 240); Vermont: Caledonia co., Peacham, South Burlington (www.inaturalist.org); Virginia: Giles County (sub lepidum, www.inaturalist.org/obs/50592574); Washington: Steilacoom (Breuning, 1928: 84), Winthrop (www.inaturalist.org); West Virginia: Tucker county (Canaan valley) (www.inaturalist.org); Wisconsis: Bayfield (NMNH), Egg Harbor, Spring Green, Delton, Luck, Monroe County (www.inaturalist.org/); Wyoming: Sheridan county (http://bugguide.net/1371896), Casper (sub lepidum, www.inaturalist.org/obs/28127777).

Notes: Winged. C. calidum is diurnal and nocturnal, active in sunshine or sheltering under debris or stones. It can be found in lowlands and midlands up to 1300m altitude. It lives in a variety of habitats: on open ground as pastures, tilled fields, vacant lots or in open forests. Adults and larvae are terricolous predators of caterpillars and other insects that sometime can damage crops.
Adults, living near a water body, have been seen, in case of danger, taking refuge in the water. According to the oldest report (Moore, 1933) a specimen, on the beach of Lake Michigan, sought refuge under a submerged stone and remained there without damages for nineteen minutes. Also more recent observations (Landry 1976) confirmed that Calosoma calidum, if threatened, enter freely under water and can remain submerged a couple of minutes.
In the northern part of its aerea of diffusion, C. calidum has been found active mostly in May – July, , overwintering in the colder season. (Lindroth, 1961: 51), but in the suthern areas it can be observed in activity from April to December
The description of the larva in all stages and of the pupa has been given by Burgess (1896: 426) and Burgess & Collins (1917: 98).

Calosoma (Chrysostigma) calidum ♂ (Fabricius, 1775) Canada: Québec, San Jean de Matha, 1.VII.76, Garneau

Calosoma (Chrysostigma) calidum ♀ (Fabricius, 1775) Canada: Manitoba, 18 km. E. of Virden, 27.6.08, Lawton

Calosoma (Chrysostigma) calidum ♂ (Fabricius, 1775) Nebraska (Typus of Calosoma lepidum) (coll. and photo: Museum of Comparative Zoology, Harvard University, Cambridge, Massachusetts, USA)

Calosoma (Chrysostigma) calidum ♂ (Fabricius, 1775) Canada: Alberta, Medicine Hat, VI, 1922 (sub Calosoma (Chrysostigma) lepidum)

Calosoma (Chrysostigma) calidum ♂ (Fabricius, 1775) Mexique (type of Calosoma mexicanum) (coll. Muséum National d'Histoire Naturelle, Paris)