Tetramorium caespitum

This is the most common European Tetramorium species. Long believed to be introduced to North America, Wagner et al. (2017) conclusively determined the North American species is Tetramorium immigrans.

Wagner et al. (2017) - Moderately thermophilic, TAS of 465 sites 16.1 ± 2.0 °C [7.9, 21.1], different from all species except Tetramorium indocile. Most common species in most of Europe and more euryoecious than other species of complex. Most records from non-forested habitats like meadows, pastures, heaths, arid or semi-arid grasslands, vineyards, fallow grounds, ruderal areas, road embankments, rock heaps, gravel pits, river banks, but also light pine and oak forests. Urban areas like parks, pavements, and roadsides. Nest construction more flexible than in other species: in soil, under stones, rarely in dead wood; only species building soil mounds higher than 10 cm.

Identification
A member of the Tetramorium caespitum complex. The species can be determined with a discriminant analysis of a set of morphological measurements. See Wagner et al. (2017) and https://webapp.uibk.ac.at/ecology/tetramorium/

Blackish brown, sometimes paler; head including clypeus and mesosoma regularly longitidinally striate. Petiole and postpetiole with shallow punctures and sculpture but smooth in centre. Propodeal spines very short, broadly denticulate, petiole and postpetiole about as broad as long. Length: 2.5-4 mm (Collingwood 1979).

Distribution
Europe, up to 63° N, Caucasus. This species does not occur in North America (Wagner et al. 2017).

Distribution based on Regional Taxon Lists
Nearctic Region: United States. Neotropical Region: Argentina, Chile, Mexico. Palaearctic Region: Afghanistan, Albania, Armenia, Austria, Balearic Islands, Belarus, Belgium, Bulgaria, Canary Islands, Channel Islands, China, Croatia, Democratic Peoples Republic of Korea, Denmark, Estonia, Finland, France, Georgia, Germany, Gibraltar, Hungary, Iberian Peninsula, Iran, Israel, Italy, Jersey, Kazakhstan, Kyrgyzstan, Latvia, Liechtenstein, Lithuania, Luxembourg, Malta, Monaco, Montenegro, Netherlands, Norway, Poland, Republic of Macedonia, Republic of Moldova, Romania, Russian Federation, Slovakia, Spain, Sweden, Switzerland, Turkmenistan, Ukraine, United Kingdom of Great Britain and Northern Ireland.

Biology
Monogynous (Seifert 2007). Hybridizes with Tetramorium immigrans (Wagner et al. 2017; Cordonnier et al. 2019).

Adult sexuals in nests on 25 June ± 14d [28 May, 19 August] (n = 67). Direct swarming behavior observed on 14 June, 15 June at 11:05 true solar time, and 30 June at 07:15 true solar time.

Collingwood (1979) - The species tends to be coastal in North Europe but also inland on heath and on the open borders of woodland, nesting in the earth and also under stones. Colonies are normally single queened, but populous with up to 10,000 or more workers. This species is moderately aggressive, living by predation on other arthropods, scavenging and also from root aphid honeydew. Seeds of various herbs and grasses are often collected into the nest. The alatae are conspicuously large compared with the workers; they are developed in the early summer and fly in late June and July.

Fungi
This species is a host for the endoparastic fungus Myrmicinosporidium durum (Espadaler & Santamaria, 2012).

Other Ants
This ant is parasitized by Tetramorium atratulum and Strongylognathus testaceus.

Nomenclature

 *  caespitum. Formica caespitum Linnaeus, 1758: 581 (w.) EUROPE. Latreille, 1798: 50 (q.m.); Mayr, 1861: 62 (q.m.); Wheeler, G.C. & Wheeler, J. 1954d: 445 (l.); Hauschteck, 1961: 221 (k.); Imai, 1966: 119 (k.). Combination Manica: Jurine, 1807: 279; in Tetramorium: Mayr, 1855: 426. Senior synonym of fuscula: Smith, F. 1851: 118, Radchenko, 2007: 31; of modesta Foerster: Curtis, 1854: 215; Mayr, 1855: 426; of fusca: Dalla Torre, 1893: 132; of transversinodis: Brown, 1949a: 47; of immigrans: Bolton, 1979: 171; of himalayanum, indocile, transbaicalense: Radchenko, 1992b: 50; of hammi: Bolton, 1995b: 405; of jiangxiense: Wu & Wang, 1995: 82; of fusciclavum: Sanetra, Güsten & Schulz, 1999: 320. Current subspecies: nominal plus barabense, caespitomoravicum, flavidulum, japonicum, pallidum, typicum. See also: Emery, 1909d: 697; Bondroit, 1918: 107; Emery, 1925c: 177; Baroni Urbani, 1971c: 135; Kutter, 1977c: 157; Arnol'di & Dlussky, 1978: 544; Smith, D.R. 1979: 1400; Collingwood, 1979: 84; Cammaerts, Pasteels et al. 1985: 109; Kupyanskaya, 1990: 151; López, 1991a: 31; López, 1991b: 73; López, et al. 1992: 169; Radchenko, Czechowski & Czechowska, 1998: 108.
 * fusca. Formica fusca Leach, 1825: 290 (q.m.) FRANCE. [Unresolved junior primary homonym of Formica fusca Linnaeus, 1758: 580.] Junior synonym of caespitum: Dalla Torre, 1893: 132.
 * fuscula. Myrmica fuscula Nylander, 1846a: 935, pl. 18, figs. 34, 36 (w.q.m.) FINLAND. Junior synonym of caespitum: Smith, F. 1851: 118; Radchenko, 2007: 31.
 * modesta. Myrmica modesta Foerster, 1850a: 49 (w.) GERMANY. Junior synonym of caespitum: Curtis, 1854: 215; Mayr, 1855: 426.
 * himalayanum. Tetramorium caespitum subsp. himalayanum Viehmeyer, 1914b: 38 (w.q.m.) INDIA. Junior synonym of caespitum: Radchenko, 1992b: 50.
 * hammi. Tetramorium caespitum var. hammi Donisthorpe, 1915d: 178 (w.) GREAT BRITAIN. Junior synonym of caespitum: Bolton, 1995b: 408.
 * immigrans. Tetramorium caespitum var. immigrans Santschi, 1927a: 54 (w.) CHILE. Junior synonym of caespitum: Bolton, 1979: 171.
 * transbaicalense. Tetramorium semilaeve subsp. transbaicalense Ruzsky, 1936: 93 (w.) KAZAKHSTAN. Junior synonym of caespitum: Radchenko, 1992b: 50.
 * transversinodis. Myrmica (Myrmica) brevinodis var. transversinodis Enzmann, J. 1946b: 47, figs. 1,2 (w.) U.S.A. Junior synonym of caespitum: Brown, 1949a: 47.
 * fusciclavum. Tetramorium caespitum var. fusciclavum Consani & Zangheri, 1952: 42 (w.) ITALY. [First available use of Tetramorium caespitum subsp. caespitum var. fusciclava Emery, 1925c: 187; unavailable name (Bolton, 1995b: 408).] Junior synonym of caespitum: Sanetra, Güsten & Schulz, 1999: 320.
 * jiangxiense. Tetramorium jiangxiense Wang & Xiao, in Wang, M., Xiao & Wu, 1988: 269, figs. 24, 25 (w.) CHINA. Junior synonym of caespitum: Wu & Wang, 1995: 82.

Worker
Wagner et al. (2017) - Larger than most species of complex, CS = 761 ± 50 [591, 867] μm. Dark brown to blackish.

Head moderately elongate, CL / CW = 1.012 ± 0.015 [0.969, 1.043]. Eye rather small, EYE / CS = 0.171 ± 0.005 [0.158, 0.188]. Scape length moderate, SLd / CS = 0.777 ± 0.015 [0.724, 0.812]. Mesosoma long and wide, ML / CS = 1.172 ± 0.026 [1.104, 1.233], MW / CS = 0.645 ± 0.015 [0.605, 0.687].

Promesonotal dorsum convex, metanotal groove shallow. – Head dorsum and occiput with longitudinal costae and costulae, in Iberia longitudinal costae and costulae of head dorsum sometimes interrupted by smooth and shiny areas. Postoculo-temporal area of head with moderate number of longitudinal costae and costulae, POTCos = 7.45 ± 1.92 [3.38, 12.13]. Mesosoma dorsum longitudinally rugulose, in Iberia longitudinal costae and costulae sometimes interrupted by smooth and shiny areas. Lateral side of propodeum with a moderately pronounced smooth and shiny area, Ppss = 39.9 ± 20.0 [13.3, 107.7]. Dorsum of petiolar node smooth or with slightly microreticulate sculpture. General surface appearance on average moderately smooth and shiny compared with other species. – Connected stickman- like or reticulate microsculpture: small units scattered over 1st gastral tergite, MC1TG = 12.62 ± 2.31 [7.00, 19.58]. – Some workers with long c-shaped, crinkly, or sinuous hairs on ventral head posterior to buccal cavity.

Male
Wagner et al. (2017) - Paramere structure belongs to caespitum-like form: ventral paramere lobe with one or two sharp corners; without distinct emargination between paramere lobes in posterior view, both paramere lobes reduced in size; in ventro-posterior view, second corner on ventral paramere lobe missing or < 87 μm apart from first. In posterior view, typically only one sharp corner on ventral lobe.

Type Material
Wagner et al. (2017) - Neotype designation: Schlick-Steiner et al. 2006. Floghult Bohuslan (Sweden), 58.97° N, 11.42° E, 100 m a.s.l., leg. C.A. Collingwood, 21.VI. 2000.