Strongylognathus bulgaricus

Distribution
The previous records of the species in Bulgaria are from northern Bulgaria – Veliko Tarnovo, Preobrazhenski Monastery (10 km from Veliko Tarnovo), Dryanovo, Veliki Preslav and one (Silistar) is on the southern Black Sea coast (Viehmeyer 1922, Atanassov and Dlussky 1992, Lapeva-Gjonova and Kiran 2012). All northern Bulgarian sites are located in the Predbalkan geographic region, in a hilly and lowland area with an average altitude of 360 m. (Lapeva-Gjonova & Radchenko, 2021)

Distribution based on Regional Taxon Lists
Palaearctic Region: Bulgaria.

Nomenclature

 * . Strongylognathus rehbinderi subsp. bulgaricus Pisarski, 1966: 515 (w.q.m.) BULGARIA.
 * Type-material: lectotype queen (by designation of Pisarski, 1966: 516), 2 paralectotype workers, 2 paralectotype queens, 2 paralectotype males.
 * Type-locality: lectotype Bulgaria: Tirnowa (F, Schimmer); paralectotypes with same data.
 * Type-depository: MNHU.
 * [First available use of Strongylognathus huberi subsp. rehbinderi var. bulgarica Viehmeyer, 1922: 211 (w.q.m.) BULGARIA; unavailable (infrasubspecific) name.]
 * As unavailable (infrasubspecific) name: Kutter, 1923: 338.
 * Synonym of kratochvili: Pisarski, 1966: 515; Kutter, 1968b: 205; Bolton, 1976: 306.
 * [Note: Pisarski, Kutter, and Bolton give bulgaricus as senior synonym, but kratochvili has priority (Bolton, 1995b: 395).]
 * Junior synonym of kratochvili: Bolton, 1995b: 395.
 * Junior synonym of christophi: Seifert, 2018: 239 (in text).
 * Status as species: Kutter, 1968b: 205; Bolton, 1976: 306; Atanassov & Dlussky, 1992: 158; Lapeva-Gjonova & Radchenko, 2021: 10.

Taxonomic Notes
Lapeva-Gjonova & Radchenko (2021) - Viehmeyer (1922) described S. huberi subsp. rehbinderi var. bulgaricus, based on all three castes from Veliko Tarnovo (northern Bulgaria), but this name is unavailable (quadrinomen). Pisarski (1966) used the first available name for this species, S. rehbinderi subsp. bulgaricus and considered it as a senior synonym of Strongylognathus kratochvili, but the latter name has priority. It was later recorded for the country under the name S. bulgaricus by Atanassov and Dlussky (1992) and under the name S. kratochvili by Lapeva-Gjonova et al. (2010).

Recently, Seifert (2018) noted, without comments, that S. bulgaricus is not a synonym of S. kratochvili, but is a junior synonym of S. christophi. In our opinion, the proposed synonymy seems doubtful: the sculpture on the head dorsum in S. christophi is much coarser, the head is relatively shorter (CI ≤ 1.10), the antennal scape is longer (SI > 0.70), the petiolar node with widely rounded dorsum and the propodeal dents are directed mostly backwards at an angle of ca. 45. On the contrary, the sculpture on the head dorsum in S. bulgaricus is strongly reduced, its head is relatively longer (CI > 1.16), the antennal scape is shorter (SI < 0.70), the petiolar node with much more narrowly rounded dorsum and the propodeal dents are directed almost upwards (Table 1 and our unpublished data; see also Forel 1900, Šilhavý 1937).

On the other hand, S. bulgaricus and S. kratochvili are very similar to each other in many subjective features (e.g. sculpture of the head and mesosoma, pilosity, shape of the propodeal dents etc.), but S. kratochvili differs from S. bulgaricus by noticeably larger body size (it is one of the largest Strongylognathus species, as Šilhavý has already emphasised). We agree with the proposed separation of these species (see Seifert 2018), but consider S. bulgaricus (at least tentatively) a good species.