Formica delinghaensis CHANG & HE, 2002

Seifert, Bernhard, 2021, A taxonomic revision of the Palaearctic members of the Formica rufa group (Hymenoptera: Formicidae) - the famous mound-building red wood ants, Myrmecological News 31, pp. 133-179 : 172-173

Formica delinghaensis CHANG & HE, 2002

Formica delinghaensis CHANG & HE, 2002 [zoogeography and description]

This taxon was described from Delingha, Qinghai Province / China (37.32° N, 97.22° E, 2750 m). CHANG & HE (2002) separated F. delinghaensis from Formica wongi by a brighter colour and a shorter scape (SL / CL 0.89 - 1.00). This scape length ratio is just the typical situation in Formica sinensis (SL / CL in 70 specimens 0.944 ± 0.027). Furthermore, only a single Formica rufa group species was discovered in E Tibet, Sichuan, and Gansu during seven collecting trips performed by A. Gebauer, D. Wrase, M. Schülke, I. Kabak, B. Seifert, R. Schultz, V. Assing, and A. Pütz in the years 1990 - 2012, and this species was F. sinensis .

All material examined. Numeric phenotypical data were recorded in 29 samples with 70 workers and seven gynes from China. For details, see SI1, SI2, and SI3.

Geographical range. Formica sinensis is found in the Chinese provinces Qinghai, Gansu, Sichuan, Chong- ging, and, as a seemingly disjunct population, in the province Jilin. Eleven samples from Quinghai and Gansu, from latitudes of 33 - 38° N, were found at elevations of 2480 ± 276 [2080, 2862] m and 11 samples from Sichuan, from latitudes between 28 - 32° N, at elevations of 3334 ± 542 [2700, 4130] m. This indication of high-altitude distribution may be partially misleading as the entomologists were not much motivated to sample in anthropogenically affected landscapes at lower elevations. A much lower alti- tudinal limit is indicated by the findings from Chongging (29.53° N, 106.52° E, 1500m), Chincheng Shan (30.90° N, 103.55° E, 975 m), and Yongij (43.7° N, 126.3° E, 560m).

Diagnosis of worker ( Tab. 5, Fig. 20 , key). Medium-sized, mean and maximum CS over all morphological and social phenotypes 1783 and 2134 µm. Head elongated CL / CW 1750 1.113. Clypeal morphology as in Formica truncorum . Scape very long and slender, SL / CS 1750 0.997, SL / Smax 1750 11.18. Petiole scale very narrow, PeW / CS 1750 0.430. Eyes with no or only short microsetae, EyeHL 1750 5µm. Dorsal plane of scape always without setae, nSc 1750 0.0. Setae number on each place of the body smaller than in F. truncorum but setae length on underside of head and metapleuron comparable: nCH 1750 8.2, nGu 1750 26.1, nPn 1750 26.6, nMes 1750 24.2, nPr 1750 20.5, nMet 1750 7.7, OccHL 1750 114 µm, GuHL 1750 184µm, mPnHL 1750 70 µm, MetHL 1750 140 µm. Dorsal surface of head without the deep and broad microfoveolae characteristic for F. truncorum . Pigmentation as in the latter.

Diagnosis of gyne ( Tab. 8). Rather large, mean CS 2192 µm. Head capsule in dorsal view less trapezoidal than in Formica truncorum , clypeal shape as in that species. Scape length and slenderness largest in all species considered here, SL / CS 0.921, SL / Smax 10.30. Petiole width as in F. truncorum , PeW / CS 0.589. Setae on eyes fully absent, EyeHL 0 µm. Setae on dorsum of scape always absent, nSc 0.0. Setae on hind margin of head much less numerous and shorter than in F. truncorum , nCH 11.4, OccHL 163µm. Gular setae less numerous than in F. truncorum but of similar length, nGu 33.0, GuHL 250µm. Setae on pronotum, metapleuron and petiole scale less numerous and shorter than in F. truncorum, PnHL 194 µm, nMet 22.3, MetHL 215 µm, nPe 11.2. Cuticular surface of head very homogenous, without pits or foveolae. Dorsum of first gaster tergite weakly shiny, with dense transverse microripples and dilute pubescence (sqPDG 10.14µm) but very homogenous microsculpture, microfoveolae often absent. Pigmentation as in F. truncorum .

Taxonomic comments and clustering results. WU (1990) separated his new taxon Formica wongi from Formica sinensis because of absence of setae from pronotum and from the first three gaster tergites and the “rather dull body”. As there are always setae on the first three gaster tergites even in the least hairy species of the Palaearctic Formica rufa group, it appeared unclear if WU’ s material really belonged to this species group. The investigation of five syntypes had the following results:

Very small body size for a species of the Formica truncorum species complex (CS = 1214, 1251, 1326, 1490, 1563µm) – this suggests a colony shortly after foundation. Ablation of pilosity on many areas of surface is confirmed by presence of numerous basal pits of setae. Anterior face of first tergite with numerous standing setae; most setae on exposed dorsal surfaces of first three tergites torn off, the few remaining are pasted flat to surface; in shel- tered surface dints numerous and long setae are present. Large parts of cuticular surface are polluted (“rather dull body”) and setae ablations are possibly due to attempts of mechanical cleaning prior preparation. Standard setae numbers and lengths were estimated in the three largest workers by scrutinizing the cuticular surface at magnifi- cations of 360 × for basal pits of setae and measuring the length of both standing setae and those glued flat to the surface. The sample means of the three largest workers are: CS 1460 µm, CL / CW 1750 1.119, SL / CS 1750 1.067, SL / Smax 1750 11.67, PeW / CS 1750 0.397, EyeHL 1750 7.3µm, nSc 1750 0.0, nCH 1750 5.1, OccHL 1750 105.6 µm, nGu 1750 31.1, GuHL 1750 130.0µm, nPn 1750 5.4, mPnHL 1750 57.1 µm, nMes 1750 22.5, nPr 1750 24.8, nMet 1750 11.4, and MetHL 1750 114.0 µm. All these data indicate a typical series of F. sinensis .

The separation of Formica sinensis and Formica truncorum was very clear in any exploratory and hypothesis-driven data analysis considering the 17 characters mentioned above ( Fig.35 ). The classification error in an LDA was 0% in 70 and 92 individual workers of F. sinensis and F. truncorum , respectively. Wild-card runs allocated all type specimens of F. truncorum , Formica truncicola , Formica approximans , and Formica yessensis to the F. truncorum cluster and all type specimens of F. sinensis and Formica wongi to the F. sinensis cluster. The classification errors in NC-Ward and NC-part.hclust were 0% and 1.6% in NC-part.kmeans.

Biology. The data collected for this revision show the following aspects: Formica sinensis is the only Formica rufa group species present in large areas of China and thus without direct competitors in a rather broad niche space. It occurs in coniferous, mixed, and broad-leafed woodland of natural or anthropogenous origin – at higher elevations preferentially in woodland with low canopy closure or on clearings. Social types vary from monodomous colonies to true supercolonies with large mounds. Six observations of alates occurred between 26 June and 5 August.

Figures

Figs.14-20: (14-lugu) Formica lugubris, worker, normal morph, head; central vertex suggestedly shiny due to weaker transverse microsculpture. (15-lugu) Formica lugubris, worker, Hippie morph, head; central vertex suggestedly shiny due to weaker transverse microsculpture. (16-helv) Formica helvetica sp.n., worker, holotype, head. (17-helv) Formica helvetica sp.n., worker, holotype, lateral. (18-trun) Formica truncorum, worker, head. (19-trun) Formica truncorum, gyne, head. (20-sine) Formica sinensis, worker, lateral; note the contrast between weak pronotal and strong gular pilosity.

Fig.35: Nest-sample means of the discriminant score and the first factor of principal component analysis of workers of For- mica truncorum (white dots) and of Formica sinensis (black rhombs) considering seven phenotypic characters. The posi- tions of the single type specimens of F. truncorum FABRICIUS, 1804 (abbreviation TM), Formica truncicola NYLANDER,1846 (TA), and Formica yessensis WHEELER, 1913 (YE) and of the type series of Formica approximans WHEELER, 1933 (AP), F. sinensis WHEELER, 1913 (SI), and Formica wongi WU, 1990 (WO) are indicated by arrows.