Formica pratensis RETZIUS, 1783 [concept of FOREL (1874), present neotype designation]
Type specimens are unknown and the original description of RETZIUS (1783), reporting only “rufa, capite abdomineque nigris, petiolo abdominis squamifero”, does not allow an identification even of the genus. The tradition which ant has to be named as F. pratensis was founded by FOREL (1874) who reported for the worker a large extension of the dark patch on dorsal mesosoma, a longer pilosity compared with Formica truncoru m, presence of setae on legs and eyes, and, for the gyne, a completely matt, densely pubescent gaster. This character combination excludes any of the other seven species occurring in Switzerland. FOREL (1874) also reported as main habitat grassland and wood margins, which probably prompted him to assign A.J. Retzius’ name to this ant. In order to stabilize the nomenclature, a neotype was fixed from a nest sample con- taining 18 workers, labelled “GER: 51.4048° N, 14.8746° E, Daubitz- 3.3 km ENE, 162 m, flacher HÜgel, R.Schultz 1999.06.30 -050” and “ Neotype Formica pratensis Retzius 1783 des. B. Seifert 2020 ”; depository SMN Görlitz.
Formica nigricans BONDROIT, 1912
Formica pratensis var. nigricans BONDROIT, 1912 [photos of lectotype, zoogeography]
This is the first available use of Formica rufa pratensis var. nigricans EMERY, 1909. EMERY (1909) reported as collecting sites “eine südliche Form; aus den Seealpen und aus Spanien, auch im Apennin (Vallombrosa)”. A lectotype was fixed in worker specimen stored in MHN Genève labelled “Cotypus”, “ Formica rufa pratensis var. nigricans Em Vallombrosa ” (C. Emery’s handwriting), “ v. nigricans Em ” (A. Forel’s handwriting), and “ MHNG ENTO 00085011”. The characters revealed in the photos in combination with zoogeography clearly indicate that F. pratensis var. nigricans is a junior synonym of F. pratensis and not of Formica lugubris. The type locality Vallombrosa (43.73° N, 11.56° E, 950 m) is situated in a geographic region, as it is with the whole Apennine, where boreomontane species of the F. lugubris species complex did not occur in the times of C. Emery (BARONI URBANI 1971). All populations of boreomontane wood ants from the Apennine mountains known today go back to a massive artificial introduction performed during the years 1959 - 67 (e.g., PAVAN 1959).
Formica cordieri BONDROIT, 1917
Formica cordieri BONDROIT, 1917 [type investigation]
This taxon was described by BONDROIT (1917) as gyne in the key. No type locality, collector, nor date was given. Examined were three type specimens from MSNB Bruxelles: one gyne labelled “Orne-6-Longny Collection E.Cordier”, “ Formica cordieri Type Bondr.”; one gyne labelled “Hte Savoie de Gaulle”, “ Formica v. cordieri Type Bondr.”, and one gyne labelled “Sayat P. de D.”, “ Formica v. cordieri Type Bondr.”. The synonymy with Formica pratensis is obvious: All three gynes belong to the hairy N-morph as defined by SEIFERT (1992). For separation of N- and P-morphs, see also below and Figure 29.
Formica grouvellei BONDROIT, 1918
Formica grouvellei BONDROIT, 1918 [type investigation]
Investigated was the type gyne from MSNB Bruxelles labelled “Digne Grouvelle”, “ F.rufa var. grouvellei Type Bondr.”. The type belongs to the hairy N-morph as defined by SEIFERT (1992).
Formica thyssei STÄRCKE, 1942
Formica pratensis ab. thyssei STÄRCKE, 1942 [type investigation]
This taxon was described from the Netherlands in a gyne collected at Eerbeek op de Veluwe, June 1916, leg. F. T. Valck Lucassen. This type from NBC Leiden was in- vestigated and belongs to the less hairy P-morph as defined by SEIFERT (1992).
Formica angusticeps STÄRCKE, 1947
Formica rufa var. angusticeps STÄRCKE, 1947 [description, zoogeography]
The taxon was described from the Netherlands. BOL- TON (1995) considered the name as available. The title of the paper “De boreale form van de roode boschmier (Formica rufa rufa)” suggests that STÄRCKE (1947) intended to introduce the new name at infrasubspecific rank. Yet, the main text did not make it clear what his intention was. If the name is available, we can assume a synonymy with Formica pratensis based on the following argumentation. The type locality is in Hoge Veluwe (51.08° N, 5.83° E, 38m) – a sand dune area with interspersed moister parts. We have only four species of the F. rufa group potentially occurring in that region: F. rufa, Formica polyctena, F. pratensis, and Formica truncorum. Formica truncorum is extremely rare in the Netherlands and STÄRCKE (1947) would have noted the diagnostic pigmentation. Therefore, he would have referred to one of the other three species. The reported presence on extensor profile of tibiae of 5 - 11 setae which are erected by 30 - 45° clearly speaks against F. rufa, F. polyctena, or F. polyctena × rufa. STÄRCKE (1947) gave no data on pilosity on back of head but he compared his F. angusticeps with specimens of “ F. rufa rufa ” from the Norwegian coast near the Lofoten (68° N) and of “ F. rufa alpina Santschi ” from the high Alps. For zoogeographical and morphological reasons, his specimens from the Lofoten obviously belonged to Formica lugubris and those from the high Alps to either F. lugubris or Formica paralugubris. These data implicate F. angusticeps to have a rich overall pilosity as it is typical for F. pratensis and to be hairier than in the hairiest F. rufa phenotypes.
Formicapratensoides GöSSWALD, 1951 Formica minor ssp. pratensoides GÖSSWALD, 1951 [description, zoogeography]
This taxon was described from near Würzburg (Germany): “Revierförsterei Irtenberg, Forstamt Waldbrunn”. GÖSSWALD (1951) reported a large, clearly demarcated black patch on promesonotum of the workers and gynes having 110 - 115% of the size of Formica rufa and a completely matt gaster surface. It becomes obvious from his lengthy treatise that GÖSSWALD (1951) studied a polygynous-polydomous colony of Formica pratensis. Such colony types up to true supercolonial conditions have been repeatedly observed in forests of the planar and colline zone of Germany (SEIFERT 1992, 2018).
Formica staerckei BETREM, 1960
Formica nigricans var. staerckei BETREM, 1960 [description, zoogeography]
It was described from a gyne collected by E. Wasman on 30 May 1885 near Castle Exaten at Baexem (Netherlands). BETREM (1960), using low-resolution microscopes, mentioned hairy eyes, absence of long hairs on head, a “practically hairless” mesosoma, and a matt surface of scutellum and gaster. This corresponds to the P-morph of Formica pratensis. The type specimen should exist in NHM Maastricht but was not available for investigation.
Formica nigropratensis BETREM, 1962 Formica nigropratensis BETREM, 1962 [unnecessary replacement name]
This new name is an objective junior synonym as it was referred by BETREM (1962) simultaneously to the available names Formica thyssei STÄRCKE, 1947, Formica pratensoides GÖSSWALD, 1951, and Formica staerckei BETREM, 1960.
A l l m a t e r i a l e x a m i n e d. Numeric phenotypical data were recorded in 96 nest samples with 331 workers and 21 gynes. These originated from Bulgaria (seven samples), Czechia (one), Georgia (one), Finland (two), France (six), Germany (37), Hungary (two), Italy (one), Kazakhstan (four), Kyrgyzstan (three), Poland (one), Romania (two), Russia (21), Sweden (seven), and Switzerland (one). For details, see SI1, SI2, and SI3. Character recording in ethanol-stored material according to the former investigation protocol of SEIFERT (1992) had been done until the year 1991 in 224 nest samples with 1756 workers and 295 gynes originating from Europe.
G e o g r a p h i c r a n g e. Continuously distributed through the temperate and submeridional zones of the Palaearctic, from Spain (9° W) to Irkutsk (104° E) at least. In Europe from 37° N (S Spain) to 63.9° N (Fennoscandia). In the Alps ascending to 1500 m (46.0° N), in the Pyrenees and Bulgaria to 1800 m (42° N), and in the Tian Shan to 2100m (42.2° N). Reports from higher elevations in Europe should be checked for confusion with Formica lugubris.
Diagnosis of worker (Tabs. 3 and 4, F i g s. 9 a n d 1 0, k e y). Dimorphic, with P and N morphs frequently occurring within the same nest. According to the data of SEIFERT (1992), then measured in ethanol-stored specimens, the less hairy P-morph had nCH 17.9 ± 5.7, OccHL 103 ± 25 µm, nHT 17.8 ± 5.7, and CS 1820 ± 220 (1050, 2250) µm in 962 workers, and the hairier N-morph nCH 28.2 ± 6.4, OccHL 132 ± 20 µm, nHT 25.1 ± 5.1 and CS 1770 ± 220 (1040 - 2180) µm in 794 workers. Large species; mean and maximum CS over all social types and both morphs in dry mounted specimens (with slight bias to selecting larger specimens) 1819 and 2239 µm. Head elongated, CL / CW 1750 1.111. Scape much longer and slender than in Formica lugubris, SL / CS 1750 0.927, SL / Smax 1750 10.66. Petiole scale clearly narrower than in F. lugubris, PeW / CS 1750 0.453. Setae number and length extremely variable but even in the least hairy phenotypes larger than in Formica rufa; separation from F. lugubris by seta characters impossible due to extreme setae polymorphism also in this species; for variance of setae data, see Tables 3 and 4. All body surfaces except the frontal triangle matt due to developed microsculpture. The blackish patch on promesonotum is often larger than on average seen in other species and is often sharply demarcated from the reddish surface.
D i a g n o s i s o f g y n e (T a b. 6; F i g s. 4, 1 1, 1 2). Dimorphic, P- and N-morphs frequently occurring within the same nest, and more clearly separable than workers. According to the data of SEIFERT (1992), then measured in ethanol-stored specimens, the less hairy P-morph had nCH 0.2 ± 0.8, OccHL 30 ± 20µm, nHT 0.6 ± 1.0, and CS 2290 ± 80 (2090, 2511) µm in 172 gynes, and the hairier N-morph nCH 16.2 ± 14.1, OccHL 218 ± 82 µm, nHT 8.4 ± 4.3, and CS 2250 ± 70 (2040 - 2400) µm in 123 gynes. Large; mean and maximum CS over all social types and both morphs in 21 mounted specimens 2296 and 2432 µm. Head moderately elongated, CL / CW 1.024. Scape much longer and more slender than in species related to Formica rufa, Formica aquilonia, or Formica lugubris, SL / CS 0.853, SL / Smax 9.75. Petiole scale relatively narrow, PeW / CS 0.628. Strong pilosity dimorphism: setae number, distribution, and length extremely variable (SEIFERT 1992). Setae on eyes always present and rather long to very long, EyeHL 46 - 86µm. The least hairy gynes of the P-morph have no setae on posterior margin of head, scape, scutellum, propodeum, petiole scale above spiracle, frontal face of first gaster tergite, and extensor profile of hind tibiae. The hairiest gynes of the N-morph have an extremely rich pilosity on nearly all body surfaces with seta length reaching 453µm on scutellum and 432µm on frontal face of first gaster tergite.All body surfaces, with exception of the frontal triangle, matt due to developed microsculpture. At magnifications> 100x, the dorsum of gaster tergites shows strong transverse microripples and a dense pubescence; sqPDG 4.0 ± 0.5.
T a x o n o m i c c o m m e n t s a n d c l u s t e r i n g r e - s u l t s. Combining big size, a long and slender scape, hairy eyes, and dense transverse microripples on gaster tergites, gynes are easily separable from any species except for the East Palaearctic sister species Formica kupyanskayae (for identification, see section “ Formica kupyanskayae BOLTON, 1995 ”, p. 163). Separation of Formica pratensis workers from those of Formica lugubris is safely possible throughout the Palaearctic range using the characters CS, CL / CW 1750, SL / CS 1750, SL / Smax 1750, PeW / CS 1750, nSc 1750, nCH 1750, OccHL 1750, mPnHL 1750, nMet 1750, and MetHL 1750. Exploratory data analyses considering these characters could clearly distinguish 225 nest samples with 1059 workers of F. lugubris from 77 nest samples with 266 workers of F. pratensis. Classification errors were 0.6% in NC-part.hclust, 0% in both NC-part.kmeans and NC-Ward (Fig. 28), and 2% in a PCA. Separation on individual level by an LDA was also very strong with only 1.6% misclassification in 1325 worker individuals.Yet, the separation of the two clusters in two-dimensional plots of LDA and PCA was not strong enough to allow conclusions on recent hybrid samples. For repeated hybridization of the two species in the past, see section “Hybrids Formica pratensis × lugubris ” (p. 174).
The strong dimorphism in Formica pratensis is most apparent in gynes. A re-analysis of the data of SEIFERT (1992) consisting of the 11 characters head width and number and maximum length of setae on posterior
margin of head, scutellum, extensor part of hind tibia, propodeum, and frontal face of first gaster tergite was performed here. As result, the setae-reduced P-morph and the hairy N-morph can be clearly clustered in a PCA after logarithmic transformation of the raw data (Fig. 29). The low percentage of doubtful (or intermediate) specimens is also indicated by the LDA that classified only 2.4% of 295 gynes with posterior probabilities <0.95. Clear arguments against considering the P-and N-morph as separate species are provided by the presence of both morphs in 21.6% of 37 nest samples and simultaneous observation of sexuals of both morphs at the same mating places (SEIFERT 1992). The same author also showed that phenotype dimorphism is correlated with ecological adaptations. He explained the demonstrated statistical differences in geographical distribution along a thermal gradient by selection of genotypes with differing climatic adaptations. According to SEIFERT (1992), the P-morph differs from the N-morph by the following traits: It constructs clearly flatter mounds for equal insolation conditions and goes to higher altitudes and latitudes. In Germany, the P-morph is rarer than the N-morph in dry habitats with typical Mediterranean elements but is more frequent than the N-morph on loamy soils.
B i o l o g y. See the species profile given by SEIFERT (2018).