Tetramorium caucasicum

A species typically found in pastures and steppic meadows.

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/

Distribution
Caucasus: Southern Russia, Georgia, and Armenia.

Distribution based on Regional Taxon Lists
Palaearctic Region: Armenia, Georgia , Russian Federation.

Biology
Wagner et al. (2017) - Less thermophilic than most other species of complex, TAS of seven sites 13.5 ± 2.8 °C [10.2, 18.2] and different from all species except Tetramorium indocile and Tetramorium impurum. Often above timberline; typical habitats are pastures and steppic meadows.

Adult sexuals in nests on 2 August (n = 1).

Nomenclature

 *  caucasicum. Tetramorium caucasicum Wagner, et al. 2017: 117, fig. 16 (w.m.) RUSSIA, GEORGIA, ARMENIA.

Worker
Larger than most other species of complex, CS = 757 ± 44 [706, 839] μm. Dark brown to blackish.

Head strongly elongate, CL / CW = 1.027 ± 0.021 [0.987, 1.052]. Eye medium-sized, EYE / CS = 0.172 ± 0.005 [0.162, 0.178]. Scape moderately long, SLd / CS = 0.779 ± 0.015 [0.749, 0.798]. Mesosoma moderately long and moderately wide, ML / CS = 1.160 ± 0.022 [1.131, 1.211], MW / CS = 0.637 ± 0.015 [0.612, 0.670].

Promesonotal dorsum convex, metanotal groove shallow. – Head dorsum and occiput with longitudinal costae and costulae. Postoculo-temporal area of head with rather many costae and costulae, POTCos = 8.71 ± 1.44 [6.17, 10.63]. Mesosoma dorsum longitudinally rugulose, lateral side of propodeum with moderately pronounced smooth and shiny area, Ppss = 45.0 ± 20.2 [16.4, 80.4]. Dorsum of petiolar node smooth or with sculpture. General surface appearance on average moderate smooth and shiny compared with other species. – Connected stickman-like or reticulate microsculpture: small units scattered over 1st gastral tergite, MC1TG = 14.47 ± 1.81 [11.64, 17.33]. – Some workers with long c-shaped, crinkly, or sinuous hairs on ventral head posterior to buccal cavity.

Male
Paramere structure belongs to impurum-like form: rounded ventral paramere lobe without any sharp corner in dorsal or ventral view but with clear division of ventral and dorsal paramere lobes, visible by deep emargination between lobes in posterior view. Sharp corner at end of ventral lobe in posterior view.

Type Material
River Bashil valley (Russia), 43.211° N, 42.987° E, 2206 m a.s.l., leg. Z.M. Yusupov, 18.VI.2009.

All type material from one nest, labeled "RUS: 43.211° N, 42.987° E River Bashil valley, 2206 m S slope, timberline, under stone Z.M.Yusupov 2009.06.18-17372". Holotype worker and two paratype workers in Senckenberg Naturkundemuseum Görlitz (Germany). Two paratype workers in Museum of Comparative Zoology, Cambridge, Massachusetts (USA), two in Natural History Museum in London (UK), two in Natural History Museum Basel (Switzerland), one in museum of Nature South Tyrol (Bozen, Italy), one in Tiroler Landesmuseum (Hall, Austria), two in Natural History Museum in Vienna (Austria), two in Budapest Hungarian Natural History Museum (Hungary), and two in Schmalhausen Institute of Zoology Kiev (Ukraine). Morphometric data of holotype in μm: CL = 714, CW = 691, dAN = 205, EL = 131, EW = 97, FL = 270, HFL = 563, MC1TG = 13.5, ML = 798, MPPL = 240, MPSP = 300, MPST = 183, MtpW = 338, MW = 433, PEH = 243, PEL = 157, PEW = 216, PLSP = 151, PLST = 171, PnHL = 183, PoOc = 286, POTCos = 8.5, PPH = 259, PPL = 111, Ppss = 57, PPW = 274, PreOc = 177, RTI = 289, SLd = 546, SPST = 134, SPWI = 185.

Etymology
Named after its distribution area, the Caucasus.

References based on Global Ant Biodiversity Informatics

 * Wagner H. C., W. Arthofer, B. Seifert, C. Muster, F. M. Steiner, and B. C. Schlick-Steiner. 2017. Light at the end of the tunnel: Integrative taxonomy delimits cryptic species in the Tetramorium caespitum complex (Hymenoptera: Formicidae). Myrmecological News 25: 95-129.