Strongylognathus dao

Two colonies of S. dao were collected in a typical Inner Mongolian steppe ecosystem dominated by various bunch of grasses (e.g., Wu & Loucks 1992). Other ants occurring in the area were Temnothorax nassonovi Ruzsky, Proformica mongolica Emery, Lasius cf. alienus, and several undetermined species of Formica and Myrmica.

Identification
Strongylognathus dao belongs to the huberi species-group and therefore differs notably from the other species described from China, Strongylognathus potanini Radchenko and Strongylognathus tylonus Wei, Xu et He, which are members of the testaceus-group.

Workers of S. dao resemble Strongylognathus koreanus Pisarski, but differ from the latter by the presence of standing hairs on the temples and genae, while such hairs are restricted to the occipital margin and occipital corners in S. koreanus. Additionally, the latter species is much lighter, orange-yellow or ochreous, and its postpetiole is relatively somewhat longer, lower and narrower (means PPL/PPH 0.81 and PPL/PPW 0.73 vs. 0.67 and 0.62 in S. dao). Workers of S. dao differ from those of Strongylognathus christophi Emery by the longer head (mean HL/HW 1.15 vs.1.10), and by the much more developed longitudinal rugosity on the sides of mesosoma. Queens (gynes) of S. dao are much smaller than those of S. christophi: HL < 0.85, HW < 0.70, ML < 1.25 vs. HL > 1.2, HW > 0.90, ML > 1.60 mm. S. christophi is distributed from southern Ukraine to Kyrgyzstan (Ruzsky, 1905; Pisarski, 1966; Radchenko, 1985, 1991, 2016) and we cannot exclude the possibility of finding this species in north-western China.

Distribution based on Regional Taxon Lists
Palaearctic Region: China.

Biology
The first colony was found during a general study on ant biodiversity. The second colony was noticed because of a large number of Tetramorium and Strongylognathus fighting close to two adjacent nest entrances A and B on July 31, 2017 around 10:00 in the morning in full sun after a rainy afternoon and evening. The area was full of dead or dying ants and it appeared that Tetramorium workers tried to block the nest entrances. At 11:05, a raiding column of dozens of S. dao workers left entrance A and rapidly entered a third nest entrance C about 50cm away. Within minutes, the entrances A and C were connected by ants travelling in both directions, and at 11:20, a S. dao worker was seen leaving entrance C and carrying a prepupa towards entrance A. Two more brood items were transported by S. dao in the same way, but presumably because of increasing soil temperatures the activity ceased rapidly and only a few fighting and dying ants were still observed between 12 and 14:00.

Nomenclature

 * . Strongylognathus dao Radchenko, Zhang & Heinze, 2017: 3, figs. 1-4, 5D (w.q.m.) CHINA (Inner Mongolia).
 * Type-material: holotype worker, 48 paratype workers, 3 paratype queens, 17 paratype males.
 * Type-locality: holotype China: Inner Mongolia, Research Station of Animal Ecology on Grassland, Chinese Academy of Sciences, 307 Provincial Road, Maodong, Xilinhaote, 44°11’04’’N, 116°27’38’’E, 30.vii.2016 (J. Heinze & Y. Zhang); paratypes: 40 workers, 3 queens, 17 males with same data, 8 workers with same data but 31.vii.2016.
 * Type-depositories: SIZK (holotype); IZAS, RURG, SIZK (paratypes).
 * Distribution: China.

Worker
(n=18), arranged as: holotype (min-max) [mean±SD]: HL 0.83 (0.81-0.90) [0.86±0.031], HW 0.71 (0.69-0.77) [0.74±0.027], FW 0.34 (0.29- 0.35) [0.34±0.014], FLW 0.34 (0.31-0.35) [0.34±0.011], SL 0.55 (0.53-0.60) [0.56±0.020], OL 0.15 (0.14-0.16) [0.15±0.006], GnL 0.24 (0.22-0.25) [0.24±0.007], TpL 0.34 (0.34-0.38) [0.35±0.012], ML 1.19 (1.09-1.20) [1.16±0.028], MH 0.45 (0.39-0.46) [0.43±0.019], PL 0.34 (0.34-0.36) [0.35±0.008], PW 0.22 (0.21-0.25) [0.24±0.011], PH 0.30 (0.28-0.33) [0.31±0.012], PPL 0.20 (0.18-0.21) [0.19±0.014], PPW 0.32 (0.29-0.34) [0.31±0.014], PPH 0.30 (0.27-0.31) [0.29±0.008], PnW 0.50 (0.49-0.55) [0.52±0.016], HTL 0.57 (0.56-0.62) [0.58±0.015]. HL/HW 1.16 (1.11-1.18) [1.15±0.017], FW/HW 0.49 (0.43-0.49) [0.45±0.015], FLW/ FW 1.00 (0.98-1.05) [1.02±0.021], SL/HL 0.66 (0.64-0.69) [0.66±0.012], SL/HW 0.76 (0.74-0.78) [0.76±0.011], PL/HL 0.41 (0.39-0.42) [0.40±0.011], PL/PH 1.12 (1.04-1.21) [1.12±0.047], PPL/HL 0.24 (0.21-0.25) [0.22±0.014], PPL/PPH 0.65 (0.60-0.75) [0.67±0.041], PPL/PPW 0.61 (0.54-0.68) [0.62±0.044], PPW/PW 1.44 (1.28-1.44) [1.33±0.055], OL/HL 0.19 (0.17-0.19) [0.18±0.007], TpL/HL 0.41 (0.39-0.43) [0.41±0.010], GnL/OL 1.55 (1.55-1.62) [1.57±0.021], AL/AH 2.66 (2.59- 2.86) [2.71±0.079]

Head moderately elongate, with very slightly con-vex to subparallel (in smaller specimens) sides, occipital margin very shallowly concave, occipi-tal corners rounded, posterio-lateral corners of the head not prominent (seen in profile). Anteri-or clypeal margin slightly convex and gradually rounded, not-notched medially. Eyes of moder-ate size, much shorter than length of genae, situ-ated approximately at midlength of sides of head. Frontal carinae short, not curved, merge with the rugae that surround antennal sockets. Frontal lobes not extended, distance between their outer margins subequal to or only very slightly larger than width of frons. Scapes quite short, gradually curved at base, by far not reaching occipital mar-gin. Shape of mandibles is typical for genus, their outer surfaces without any teeth or protuberances.

Mesosoma long and low, ca. 2.6-2.9 times longer than height, with distinct while not deep metanotal groove, promesonotum very fee-bly convex, promesonotal suture at least partly developed (seen from above). Propodeum with short sharp triangular denticles. Petiole with dis-tinct but relatively short peduncle, only slightly longer than high, anterior surface of node strong-ly concave, posterior one convex, dorsum of node rounded, without dorsal plate, so that peti-ole does not appear cuneiform. Postpetiole with gradually rounded dorsum, does not appear cu-neiform, distinctly higher than length, ca. 1.3-1.4 times wider than petiole. Middle and hind tibiae with simple spur.

Central part of head dorsum smooth and shiny, but with scattered shallow piligerous fove-ae; frons in most specimens additionally with fine longitudinal striation, but occasionally striation might be reduced in various extent to complete absence; surface of head dorsum on either sides of frons and lateral part of head densely punctate and with longitudinal rugulosity. Central part of clypeus smooth and shiny.

Mesosoma and waist densely and quite coarsely punctate, short sinuous rugulae present only on mesopleura; central band on promesonotal dorsum often with partly reduced sculpture, seems quite shiny. Gaster smooth and shiny. Whole body (including occipital margin of head, temples and genae) with numerous straight, not long and blunt standing hairs, legs with subdecumbent to suberect hairs, scape with abundant short subdecumbent hairs. Mesosoma reddish-brown, head darker, dark brown to blackish-brown, appendages and mandibles somewhat lighter, reddish- to yellowish-brown. First gastral tergite completely brownish, without lighter spot at the base.

Queen
(n=2), arranged as min-max: HL 0.80-0.81, HW 0.67-0.69, FW 0.33- 0.35, FLW 0.34-0.35, SL 0.52-0.53, OL 0.18- 0.19, GnL 0.20, TpL 0.32-0.34, ML 1.20, MH 0.56, PL 0.39, PW 0.27, PH 0.36, PPL 0.20, PPW 0.42-0.43, PPH 0.38-0.39, SCW 0.66-0.67, SCL 0.90, HTL 0.53-0.54; HL/HW 1.18-1.19, FW/HW 0.48-0.52, FLW/FW 1.00-1.04, SL/HL 0.65-0.66, SL/HW 0.77-0.78, PL/HL 0.48-0.49, PL/PH 1.08, PPL/ HL 0.24-0.25, PPL/PPH 0.52-0.52, PPL/PPW 0.45-0.48), PPW/PW 1.56-1.58, OL/HL 0.23, TpL/HL 0.40-0.41, GnL/OL 1.04-1.08, AL/AH 2.15, SCL/SCW 1.33-1.36.

Very small, sizes of head and mesosoma comparable to those of workers. Head rather elongate, relatively somewhat longer than in workers, with subparallel sides, occipital margin almost straight, occipital corners rounded, posterio-lateral corners of the head not prominent (seen in profile). Eyes rather big, a little shorter than length of genae, situated approximately at midlength of sides of head. Shape of scapes, clypeus, mandibles, frontal carinae and frontal lobes as in workers.

Mesosoma quite long and low, 2.15 times longer than height, scutum and scutellum flat, scutum does not overlap pronotum. Propodeum with short triangular denticles. Shape of petiole similar to workers, but postpetiole much higher, ca. twice higher than its length and higher than petiole; more than 1.5 times wider than petiole. Legs shorter than in workers. Middle and hind tibiae with simple spur.

Head dorsum with longitudinal rugosity. Rugae of frons from the level of ocelli curving laterally and then back, confluent with rugae on ventral part of head, so that in lateral view rugosity seems concentric. Surface between rugae on frons with scattered rather big foveae and with fine punctures, space between frons and eyes, as well as genae, with much coarser and denser punctation. Clypeus smooth and shiny.

Scutum and scutellum with longitudinal rugosity. Propodeum, mesopleura, pronotum and waist densely and coarsely punctate, pronotum additionally with longitudinal rugulosity. Gaster smooth and shiny. Whole body (including occipital margin of head, temples and genae) with numerous straight, not long standing hairs, legs and scape with subdecumbent hairs. Whole body dark reddish-brown, appendages and mandibles lighter, reddish- to yellowish-brown. First gastral tergite completely brownish, without lighter spot at the base.

Male
(n=7), arranged as min-max [mean±SD]: HL 0.63-0.71 [0.68±0.028], HW 0.60-0.64 [0.62±0.016], SL 0.29-0.32 [0.30±0.013], OL 0.27-0.29 [0.28±0.008], GnL 0.05-0.06 [0.06±0.005], TpL 0.25-0.31 [0.27±0.024], ML 1.82-1.95 [1.90±0.047], MH 1.02-1.08 [1.06±0.020], PL 0.45-0.49 [0.47±0.016], PW 0.29-0.32 [0.30±0.013], PH 0.24-0.28 [0.27±0.015], PPL 0.32-0.35 [0.34±0.015], PPW 0.42-0.45 [0.43±0.012], PPH 0.38-0.41 [0.39±0.012], SCW 0.95-1.12 [1.01±0.062], SCL 1.33-1.53 [1.41±0.069], HTL 0.94-0.98 [0.97±0.016]. HL/HW 1.02-1.14 [1.09±0.039], SL/ HL 0.42-0.47 [0.45±0.017], SL/HW 0.47-0.51 [0.49±0.015], PL/HL 0.65-0.74 [0.69±0.043], PL/PH 1.60-2.06 [1.75±0.160], PPL/HL 0.47-0.56 [0.51±0.039], PPL/PPH 0.85-0.89 [0.86±0.016], PPL/PPW 0.72-0.83 [0.78±0.051], PPW/PW 1.30-1.59 [1.47±0.106], OL/HL 0.39-0.45 [0.41±0.021], TpL/HL 0.37-0.43 [0.40±0.022], GnL/OL 0.17-0.21 [0.19±0.015], AL/AH 1.75-1.83 [1.80±0.030], SCL/SCW 1.40- 1.62 [1.50±0.082].

Head longer than width, while ratio of HL/HW is quite variable (1.02-1.14), narrowing behind eyes, occipital corners widely rounded but well-marked, occipital margin straight or very feebly convex, posterio-lateral corners of head not prominent (seen in profile). Anterior clypeal margin slightly convex and rounded, not-notched medially. Eyes rather big, ca. 5 times longer than genae, situated distinctly in front of sides of head. Frontal carinae short, not curved, merge with the rugae that surround antennal sockets, frontal lobes somewhat extended. Scapes short, gradually curved at base, shorter than second funicular segment. Shape of mandibles is typical for genus, their outer surfaces without any teeth or protuberances.

Mesosoma quite high, scutum somewhat convex, overlapped pronotum, Mayrian furrows well developed, propodeum with short blunt tubercles. Shape of petiole quite variable, its node could be higher or lower, but in general 1.6-2.1 times longer than height, postpetiole ca. 1.5 times higher than petiole. Legs long and slender, middle and hind tibiae with simple spur.

Head dorsum coarsely and densely punctate, frons additionally with longitudinal rugulosity, clypeus with coarser rugae. Anterior and dorso-lateral surfaces of scutum smooth and shiny, its dorsal surface and scutellum finely and densely longitudinally ruguloso-punctate. Mesopleura, latero-ventral surface of scutum, propodeum and waist densely and coarsely punctated (sculpture on mesopleura occasionally somewhat reduced); dorsal surface of propodeum additionally with longitudinal rugosity, its posterior and lateral surfaces transversally rugose.

Body (including head margins) with numerous long, thin standing hairs, legs and scapes with subdecumbent pilosity. Head, mesosoma and waist from dark reddish-brown to brownish-black, gaster somewhat lighter, appendages and antennae ochreous.

Stipites of genitalia very feebly curved, with fine constriction in basal third, their apices rounded, not excavated.

Type Material


Paratypes: ca. 40 workers, 3 gynes and 17 males from the nest of holotype; 8 workers, collected on July 31, 2016 from a second nest in soil during a raid approximately 300 m away from the other nest (SIZK, National Zoological Museum of China, University of Regensburg, Germany). Unique specimen identifiers are: holotype worker – CASENT0916954, paratype gyne – CASENT0916955, paratype male – CASENT0916956 (all these are preserved in SIZK).

Etymology
The species name refers to the Chinese saber dāo (刀), which in shape resembles the falcate, saber-shaped mandibles of Strongylognathus in general.