Formica fennica

A polycalic colony comprising 40 nests was found near Puhos/Finland on 13 July 1996. It spread over a fresh-dry grassland that was situated between the southern margin of a medium-aged Betula wood and the S-exposed slope of a road ditch. Plant species growing near the nests were Dianthus sp., Prunella sp., Galium sp., Melampyrum nemorosum, Dactylis glomerata, Potentilla erecta, Scabiosa sp., Alchemilla sp. The nest construction was of typical Coptoformica type and the largest nest mound measured 70 × 45 cm (diameter by height). Queens were deep in the soil and only three dealate queens could be collected at ground level. The Caucasian sample of fennica was found on a short-grassy, 20°N-exposed mountain pasture at 1600 m and collected from an isolated monodomous colony. The large size of the workers in this nest strongly suggests monogyny. (Seifert 2000)

Identification
Seifert (2000) - Close relationship of Formica fennica to Formica manchu is indicated by the similarity of workers. The two taxa differ from all other Palaearctic Coptoformica species by significantly longer heads (CL/CW 1.067-1.073). F. manchu and fennica further share the character combination of conspicuous eye hairs (mean EyeHL 23-28 μm), complete absence of setae from first gaster tergite (mean TERG 2.9-3.4), rare occurence of setae in the ocellar region, and very dilute tergite pubescence (mean sqrtPDG 7.6-7.9).

The Formica manchu cluster represented by seven nest samples with 34 workers from Mongolia, N Tibet, and Manchuria differs from the W Palaearctic fennica cluster represented by six nest samples with 27 workers by significantly larger SL/CL (p < 0.0001) and by significantly smaller TERG (p < 0.001), nHTFL (p < 0.0001), and sqrtPDF (p < 0.0001). The manchu workers constantly show an additional set of conspicuous setae in the anterior portion of the sculptured surface of third tergite and the setae on outer hind tibial flexor margin are shorter, finer, and less numerous than in fennica (compare Figs 2, 17C and 18C). In the fennica workers, setae may be present at the caudal margin of third tergite but never in the anterior portion of the sculptured surface of third tergite. A numeric separation of the fennica and manchu workers is possible with by a linear discriminant score D(4) calculated as D(4) = 0.155 sqrtPDF + 0.134 TERG + 0.064 nHTFL-0.416 SL/CL.

Formica fennica differs from Formica bruni by the much longer and much more dilute frontal and tergite pubescence, by the longer head, and the larger nHTFL; sometimes the acute occipital corners may be diagnostic.

The differences between the workers of fennica and bruni are repeated in the queens. An additional difference is the significantly larger body size of the fennica queens.

Single workers of extremely pilosity-reduced Formica exsecta morphs may be confused with fennica. However, nest sample means of three workers provide a save separation with the characters nCOXA (exsecta 2.6-15.5, fennica 0.4-1.4), TERG (exsecta 1.0-2.33, fennica 3.0-4.0), OceSet (exsecta 0.33-1.0, fennica 0-0.33), and ClySet (exsecta 2.0-4.5, fennica 1.0-2.0) as confirmed for 88 nest samples of exsecta and six nest samples of fennica. The usually more acute occipital corners of fennica are no reliable discriminator from exsecta because of big intraspecific variability of head shape in Coptoformica.

Males: Eyes with numerous long hairs; EyeHL 30-45 μm. Clypeus without setae of third to fifth level; ClySet 1-2. Mesosoma with few semierect setae. Craniad profile of forecoxae with three to five standing setae. Pubescence in the ocellar triangle and on second gaster tergite dilute and long; sqrtPDF 4.1-4.6, sqrtPDG 5.0-7.3. Head elongated; CL/CW 0.853 ± 0.017. Separation from pilosity-reduced males of Formica exsecta difficult.

Seifert (2019) provides details for separating this species from the morphologically similar Formica exsecta.

Distribution
Seifert (2000) - F. fennica is apparently a continental, north temperate-montane faunal element. The type localities in Finland and Caucasus probably represent the western border of distribution.

Distribution based on Regional Taxon Lists
Palaearctic Region: Azerbaijan, Finland, Georgia, Norway, Russian Federation.

Nomenclature

 *  fennica. Formica fennica Seifert, 2000a: 534, figs. 1F, 2-5, 12 (w.q.m.) FINLAND.

Worker
Medium-sized species (CL 1340 ± 110, 1087-1514; CW 1257 ± 106, 1012-1426). Head with acute and well-pronounced occipital corners (Fig. 1F) and significantly longer than in other European species (CL/CW 1.067 ± 0.016, 1.036-1.103). Scape of average length (SL/CL 0.989 ± 0.021, 0.945-1.035). Setae only present on anterior clypeus (Fig. 3, ClySet 1.67 ± 0.56,1-3). Lateral semierect setae in the ocellar triangle rarely present (OceSet 22%). Eye hairs strongly developed (EyeHL 23.2 ± 3.1, 17-30). Pubescence hairs in the occellar triangle long and very sparse (sqrtPDF 6.68 ± 0.67, 5.19-8.19; Figs 4; 12). Craniad profile of forecoxae without or very few subdecumbent setae (nCOXA 0.91 ± 0.83, 0-3). Dorsal mesosoma, lateral metapleuron and ventrolateral propodeum without standing setae (nMET 0.0 ± 0.0). Outer edge of the hind tibial flexor side with well-developed subdecumbent setae and subdecumbent pubescence (Fig. 2, nHTFL 8.13 ± 2.33, 4.0-14.0). Semierect setae on gaster tergites beginning at the posterior border of third to fifth tergite (TERG 3.37 ± 0.56, 3-5), anterior part of third tergite always without setae. Pubescence density on first gaster tergite very low (sqrtPDG 7.89 ± 0.46, 6.99-8.73).

Queen
Rather large, in size between Formica exsecta and Formica bruni (CL 1543 ± 47, 1490-1582; CW 1520 ± 26, 1492-1544; ML 2611 ± 53, 2551-2651). Head significantly slender than in exsecta (CL/CW 1.015 ± 0.014, 0.999-1.025), scape of average length (SL/CL 0.918 ± 0.008, 0.911-0.927). Setae restricted to anterior clypeus (ClySet 1.67 ± 0.58, 1-2). Clypeus lateral of the tentorial pit level with pubescence hairs surpassing the anterior margin by more than 10 μm. Lateral semierect setae in the ocellar triangle absent. Eye hairs long (EyeHL 35.3 ± 5.5, 30-41). Pubescence in the occellar triangle decumbent, very long, and sparse PDF 6.07 ± 0.73, 5.55-6.91). Occipital corners of head with long, decumbent to almost appressed pubescence (OccHD 27.7 ± 2.1, 26-30). Dorsal head surface relatively matt and weakly sculptured (GLANZ 1.33 ± 0.29, 1.0-1.5). Craniad profile of forecoxae without or very few semierect setae (nCOXA 0.67 ± 0.76, 0-1.5). Mesonotum with decumbent to appressed pubescence and without real setae (MnHL 63.6 ± 53.2, 0-97, these are long pubescence hairs). Outer edge of the hind tibial flexor side with numerous subdecumbent setae and long decumbent pubescence (nHTFL 9.50 ± 1.80, 8.0-11.5). Semierect setae on gaster tergites beginning on the fourth tergite (TERG 4.0±0.0). Pubescence on first gaster tergite long and very sparse (sqrtPDG 8.11 ± 0.81, 7.47-9.02).

Type Material
1 queen holotype and 6 worker paratypes are labelled “FIN: 62.07N, 29.48E, road No. 71, Kitee-17W, Puhos-6.5WNW, leg. Seifert 1996.07.13-119”; 1 queen paratype, 5 worker paratypes from the same polycalic colony and same date but different nest number “FIN...1996.07.13-86”; 3 male paratypes, 6 worker paratypes from the same polycalic colony and same date but different nest number “FIN...1996.07.13-105”; 5 worker paratypes labelled “FIN: 63.27N, 27.10E, Iisalmi-13 km S, Kotikylä, 1998.07 leg. J. Sorvari”; 7 paratype workers labelled “CAU: 42.23N, 45.42E, Schenako, 1600 m, 1985.08.01, 20°N-exp. Kurzgrasige Weide”. All these mounted type specimens (plus 55 worker paratypes in ethanol) are stored in SMN Goerlitz. In the collection of Turku are stored 1 paratype queen “FIN: 62.07N, 29.48E, road No. 71, Kitee-17W, Puhos-6.5WNW, leg. Seifert 1996.07.13” and 1 worker paratype “FINLAND: Ilomantsi, Maukkula (695: 69)”.