Temnothorax crasecundus

Nests were found on ground of deciduous or coniferous forests in microspaces such as hollow acorns, nuts, rotten twigs or galls. Nest populations are monogynous (Seifert & Csősz 2015). Specimens collected from Daba, Georgia were the host of the slave-making ant Temnothorax tamarae (Csösz et al., 2015).

Identification
Seifert & Csősz (2015) - Simple separation of T. crasecundus and Temnothorax crassispinus, two very similar species, by single characters is not possible. There is considerable overlap in each of the 29 shape characters and absolute size and a much larger one on individual level. The complex species delimitation procedures outlined require much training of the investigator and a high-quality optical equipment. Even then, data recording for a single nest sample composed of three workers needs 100–120 minutes. In order to allow a practitioner of biodiversity or ecosystem research a more easy approach to the problem, we developed a more simplified determination rule using six absolute measurements. With all measurements given in mm, the discriminant D(6) = 22.058*PoOc+17.640*SL-66.166*SPST+38.233*MW-28.926*PPW -35.873*SPTI-1.797 classified 203 nest samples with an error of 3.4%. Samples with an arithmetic mean of D(6) < 0 are determined as T. crassispinus and those with larger values as T. crasecundus. With PoOc, SL and SPST being recorded bilaterally, a trained investigator needs for the resulting nine measurements about 15 minutes per individual.

The most simple means for separation of T. crasecundus from Temnothorax nylanderi is geography: the shortest distance between a site of both species is 1000 km and a closing of this broad gap is prevented by habitat saturation of the omnipresent, highly competitive T. crassipinus. A rather simple phenotypical species delimitation is possible using three absolute measurements. With all measurements given in mm, the discriminant D(3) = 129.53*SPBA–120.88*PPW+133.8*MpGR +4.446 classified 87 nest samples with an error of 3.4%. Samples with an arithmetic mean of D(3) < 0.64 are determined as T. nylanderi and those with larger values as T. crasecundus.

Csösz et al. (2015, for the Ponto-Mediterranean Temnothorax nylanderi group) - This species is easily confused with its parapatric relative, Temnothorax crassispinus. The D4 function that separates these two species is given under the latter. Temnothorax crasecundus shares most of its surface sculpturing and general shape characteristics with Temnothorax helenae, despite the fact that they belong to different species complexes based on molecular phylogeny and morphometrics. In addition, the distribution of these species broadly overlaps in Bulgaria, Greece, and Turkey. A simple ratio (PoOC/NOH) yields a rather reliable discrimination with minor overlap between them. Other characters may also help in correct determination: T. crasecundus is larger (CS), has a wider frons (FRS/CS), higher petiolar node (NOH/CS), and longer propodeal spines (SPST/SC) than T. helenae.

Distribution based on Regional Taxon Lists
Palaearctic Region: Armenia, Bulgaria, Georgia, Greece, Romania, Russian Federation, Turkey, Ukraine.

Nomenclature

 *  crasecundus. Temnothorax crasecundus Seifert & Csősz, 2015: 43, Figs. 11-14 (w.) BULGARIA.

Worker
All morphometric data given in the following verbal description are arithmetic means of 256 worker individuals calculated by fusing Seifert’s and Csösz’s data sets. Harmonization of the different data sets has been performed by the function CW = 1.0791 * CWb.

Medium-sized species (CS 641 μm, ML 760 μm). Head weakly elongated but significantly more than in Temnothorax crassispinus (CL/CW 1.069 vs. 1.055, CL/CWb 1.153 vs. 1.139). Head in dorsal aspect with strongly convex postocular sides, convex genae and straight posterior margin. Eyes with a moderate distance from posterior margin of vertex (PoOc/CL 0.391) and medium-sized in terms of the genus but significantly smaller than in T. crassipinus (EYE/CS 0.210 vs. 0.216). Scape moderately long (SL/CS 0.762, SL/CSb 0.793) and with variable pubescence: with the scape directed caudad, pubescence is appressed to decumbent (0–15°) at inner margin and more subdecumbent (30°) at outer margin. Frontal carinae rather distant (FRS/CS 0.361), their median part more or less parallel. Sculpture on central vertex regularly longitudinally carinulate. A transversal line between the frontal carinae, positioned immediately posterior of the frontal triangle, crosses 21–23 carinulae. A small longitudinal zone on median vertex occasionally without sculpture and shining. Lateral vertex and head with a more irregular sculpture, being a mixture of microreticulate and rugulose structures. Antennal sockets on shining ground surrounded by 7–8 concentric rugulae. Clypeus between sagittal level of frontal carinae rather smooth but with 5–8 longitudinal carinulae. Frontal triangle with very delicate microsculpture and 0–4 longitudinal carinulae.

Mesosoma moderately wide (MW/CS 0.608) and metanotal depression always developed (MpGr/CS 2.1%). Propodeal spines rather long and acute but distinctly shorter than in T. crassipinus (SPST/CS 0.283 vs. 0.322). Distance of their bases and tips rather large but significantly smaller than in T. crassipinus (SPBA/CS 0.286 vs. 0.300, SPTI/CS 0.324 vs. 0.353), spine tips slightly curving inwards. Direction of spines in lateral view deviating from longitudinal axis of mesosoma by 26–29°. Mesosoma irregularly microreticulate-rugulose with few superimposed longitudinal rugae on promesonotum. Metapleuron more regularly longitudinally carinate-rugose.

Petiole in lateral view rather high and with a weakly concave frontal face; the anterior profiles of node and peduncle form an angle of about 150–155° whereas anterior and dorsal profiles of node form an angle of 90–105°. Dorsal profile of node weakly convex or nearly straight and moderately long, steeply sloping down to caudal cylinder. The profiles of this slope and of the caudal cylinder form an angle of about 140°. Whole surface of petiolar and postpetiolar nodes microreticulate with a mesh width of 9–13 μm. Two longitudinal rugae typically demarcate the margin of dorsal petiolar plane while the sides of petiolar tergites are stabilized by one longitudinal carina/ruga on each side. Overall body color dirty yellow to light brown with a strong yellowish component.

Mesosoma, appendages, waist and basis of first gaster tergite usually lighter yellow to dirty yellow. Head dorsum and the posterior surfaces of gaster tergites usually darker, generally yellowish brown. Lighter heads occur.

Type Material
The worker holotype is labelled “BUL: 42.6785°N, 23.3508°E Sofia, 586 m, Borisova gradina Park, Part 2 V.Antonova 2004.05-509” and “Holotype Temnothorax crasecundus Seifert & Csösz”. Four worker paratypes, two males and two gynes from the holotype nest are mounted on two other pins and carry the same collecting data label and “Paratypes Temnothorax crasecundus Seifert & Csösz”. A second series with five worker paratypes on two pins is labeled “BUL: 42.6797°N, 23.3417°E Sofia, 596 m, Borisova gradina Park, Part 1 V.Antonova 2004.05-841” and “Paratypes Temnothorax crasecundus Seifert & Csösz”. These two type series are stored in Senckenberg Museum of Natural History Görlitz. A third paratype series containing three workers on the same pin, is labelled “Bulgaria_28: East Rhodopes, 2 km SE Novakovo 25 km SE. Asenovgrad, 1299, 400mH, 41°53'12"N, 25°5'55"E, 12.06.2009, Leg A Schulz”, “ANTWEB CASENT 0906045“ and is stored in the Hungarian Museum of Natural History Budapest.

Etymology
In the provisional internal naming system of the senior author the new species had been designated over the years as “Temnothorax crassispinus sp. 2”. The taxonomic name, composed of “cra” (first syllable of crassispinus) and “secundus” (= the second), intends to indicate both this history and the close relationship.