Formica minor GÖSSWALD, 1951

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 : 155-156

Formica minor GÖSSWALD, 1951

Formica minor GÖSSWALD, 1951 [description]

This taxon was described from near Würzburg / Germany. GÖSSWALD (1951) apparently did not define type specimens but everything he reported in his lengthy treatise makes clear that he meant Formica polyctena .

All material examined. The full set of numeric phenotypical data was recorded in 58 nest samples with 314 workers and 33 gynes; for details, see SI1, SI2, and SI3. The total number of mounted samples stored in SMN Görlitz and investigated either subjectively or by partial or complete numeric recording of the phenotypical characters used here was 69. These included 329 workers and 32 gynes and originated from Belgium (one), Finland (10), France (one), Germany (45), Poland (one), Russia (four), and Switzerland (seven). Character recording in ethanol-stored material according to the former investigation protocol of SEIFERT (1991) was done until the year 1993 in further 176 nest samples with about 1800 workers largely from Germany and the Moscow region.

Geographic range. Whole range apparently similar to that of Formica rufa : Iberia to Lake Baikal. The clearly confirmed occurrence in Europe extends between 42° N und 61° N; absent from British Isles, Asia Minor and Caucasus. The northern distributional border in Fennoscandia and Siberia and the upper altitudinal limit in Central European mountains are not exactly known because of frequent confusion with Formica aquilonia and occurrence of F. aquilonia × polyctena hybrid populations. The putative northern limit in Finland is at 63° N or along the -10 °C January isotherm. Natural distribution in the Giant Mountains ( Czechia) up to 800 m (here artificially introduced at 1020 m), in the Alps ascending to 1200 m at least.

Diagnosis of worker ( Tab. 1 , key). Clearly smaller than Formica rufa , mean and maximum CS over all social types 1669 and 2067µm. Scape rather long and slender, SL / CS 1750 0.932, SL / Smax 1750 9.97. Setae on eyes short, EyeHL 1750 17µm; on posterior margin of head nearly always missing and, if present, usually of minute size; gular, pronotal, mesopleural and propodeal setae sparse and rather short, nGu 1750 1.46, GuHL 1750 51 µm, nPn 1750 2.5, mPnHL 1750 30 µm, nMes 1750 5.9, nPr 1750 2.3; setae on metapleuron usually absent. Pigmentation as in F. rufa but percentage of dark pigmentation on mesosoma on average slightly higher due to smaller size and positive allometry of reddish pigmentation.

Diagnosis of gyne ( Tab. 6 , Fig. 2 ). Rather small; mean and maximum CS 2037 and 2165 µm; scape rather long and slender, SL / CS 0.864, SL / Smax 9.17. Setae on eyes short, EyeHL 21 µm; setae on posterior margin of head and gula always missing; pronotum bare, exceptionally without single short setae of up to 42 µm length; meso- and metapleuron and frontal face of first gaster tergite without setae, if single setae are present these may have 60 - 80 µm length; ventral surface of first gaster sternite with fewer setae than in Formica rufa , nSt 6.2, StHL 122 µm. Pubescence distance and distance of foveolae on paramedian dorsum of first gaster tergite high, sqPDG 12.2, FodG 58µm. Shiny surface of scutellum usually restricted to a small median stripe. Dorsum of gaster viewed at lower magnification shiny but usually less than in F. rufa , which is caused by very faint transverse microripples. In some specimens the microripples may be stronger developed somewhat reminiscent of the situation in Formica pratensis . Colouration as in F. rufa .

Taxonomic comments and clustering results. For separation from Formica rufa and hybrids / backcrosses Formica polyctena × rufa , see section “ Formica rufa LINNAEUS, 1761 ” (p. 152) and for separation from Formica aquilonia and hybrids / backcrosses F. aquilonia × polyctena , see section “ Formica aquilonia × polyctena – hybrids and backcrosses” (p. 156).

Biology. See the condensed information in SEIFERT (2018).

Figures

Fig.2: Formica polyctena, gyne; paramedian surface of the dorsum of first gaster tergite. There is some trend to show stronger transverse microripples and a more dilute pubescence than Formica rufa.