Formica foreli

Nests in open areas, typically with a nest mound that is covered by small pieces of cut up plant material. In open sites with sandy soil the mound may be entirely made of sand and devoid of plant material.

Identification
Seifert (2000) - The holotype specimen of Formica foreli was collected by Forel at Vaux near Morges/Switzerland and is still present in MCSN Genova. Bondroit (1918) stated that queens of foreli are different from those of Formica pressilabris by the dull body surface, the slightly larger size, and the more dense gaster pubescence, i.e. his differential diagnosis is in agreement with the species conception presented below as it is in agreement with the investigation of Emery’s type worker.

The worker of foreli differs by a much more dense frontal pubescence, a significantly denser tergite pubescence, the more caudal position of tergite setae, and a longer scape. In these diagnostic characters, the holotype specimen of foreli fits very well to the population average with SL/CL 1.025, Terg 4.0, sqrtPDF 4.59 and sqrtPDG 6.07.

Males: Hairs on eyes almost absent or very sparse; EyeHL 5-20 μm. ClySet 1. Mesosoma with nearly appressed pubescence and without semierect setae. Craniad profile of forecoxae without standing setae. Pubescence in the ocellar triangle very dense and short; sqrtPDF 3.13-4.05. Scape long; SL/CS 0.922 ± 0.033. Almost inseparable from pilosity-reduced males of Formica bruni.

Distribution
Seifert (2000) - N Spain, N Italy, Anatolia, the Caucasus, the W Alps, S Moravia, and W Slovakia. Reliable records from the German countries refer to an isolated population in Thüringen, two local populations in N Sachsen, larger populations in Brandenburg and the southern Mecklenburg-Vorpommern, and two local populations in Schleswig-Holstein. An isolated northern population exists in NE Zealand/Denmark and Skåne/S Sweden with nine sites known. The population in the W Alps is restricted to valleys with xerothermous local climate in altitudes of 1181 ± 348 m (552-1780), (n = 10). In more southern latitudes (Anatolia) it goes up to 2200 m.

Distribution based on Regional Taxon Lists
Palaearctic Region: Albania, Andorra, Austria, Belgium, Croatia, Czech Republic, Denmark, Georgia, Germany, Iberian Peninsula, Norway, Poland, Russian Federation, Spain, Sweden, Switzerland, Turkey.

Habitat
Seifert (2000) - F. foreli is a species of open oligothrophic and xerothermous grasslands mainly on sand, but also on limestone and other geological outcrop. The different zoogeography and much more expressed xerothermy of foreli compared to pressilabris is reflected by plant sociology. In all habitats studied at least some indicator plants for strong xerothermy such as Festuca cinerea, Festuca ovina, Euphorbia cyparissias, Hieracium pilosella, Echium vulgare, or Eryngium campestre were present. Very strong polycalic colonies in Brandenburg were observed to extend their nesting area into mesophilic grassland and light woodland but became extinct in the latter after full closure of the canopy.

Zones of geographic overlap with Formica foreli are rather small and known from S Sweden, W Slovakia, and the W Alps. F. foreli usually occurs below 1600 m and is preferentially a species of warm valleys on spots with very xerothermous mediterranean floral elements. F. pressilabris, in contrast, mainly occurs in altitudes of 1750-2250 m and is a species of thermophilic mountain meadows and pastures with elements of boreo-alpine flora. Vaux near Morges, the type locality of foreli, is situated at 552 m.

Biology
Seifert (2000):

Status as threatened species
Formica foreli is one of the most endangered species of the group. In Switzerland it is threatened by extinction. In Germany it has the same status, though the populations in Brandenburg and Mecklenburg-Vorpommern seem less endangered. The habitat destruction is mainly caused by intensive use of mineral fertilisers and liquid manure, high athmospheric nitrogen immission, decline of sheep pasturing and traditional cut-meadow management, intensifying of cattle pasturing, and afforestation programs.

Colony foundation
Four pins with Formica foreli workers from the type series of Formica naefi (labelled “Bain Jonnair, 10.7.54, Kutter-/”) carry four workers of Formica lemani and one worker of Formica lusatica. The equal labelling should indicate a nest sample but the mode of sampling is not explicitly stated. Observations of Kutter (1957, 1969) in an laboratory arena with nests of lemani and foreli (his naefi) showed an eudulotic behaviour of foreli with subsequent killing of the lemani queen. It seems possible that eudulotic behavior can also occur in nature (callows at least can be taken) and that mixed nests must not necessarily indicate a preceding socially parasitic colony foundation by a single foreli queen. Habitat selection and zoogeography of foreli should exclude lemani as primary host species except for few alpine populations. The main host species in the whole geographic range is unknown, but is likely to be a (de la Mora et al., 2021; Seifert, 2018), probably Formica fusca, Formica cunicularia or Formica rufibarbis.

Nest construction
There is no difference from the normal Coptoformica type. The mounds do not reach the size known for exsecta and their diameter is usually < 50 cm. The diameter of the subteranean part of the largest nest was 80 cm. On very xerothermous spots of sand dunes or sandy moraines, where the field layer is very sparse, nests may entirely lack any vegetable cover and are only circumscribed by simple entrances in the soil surface. Nests in an intensive sheep pasture near Carwitz/Germany had constucted their subterranean galleries within the solidified root bale of vegetation to increase the resistance against trampling.

Demography of nests and colonies
No reliable information on the nest population is available but figures similar to bruni are expected. The tendency towards polygyny and polycaly is very expressed. The largest polycalic colonies in Brandenburg comprised 100 nests/2500 m2 and 78 nests/1200 m2. Polycalic colonies have a sex ratio > 1 and produce mainly micraners.

Swarming
Alates were observed in the nest 14.2 July ± 24.9 d (12 June-24 Aug, n = 10) which is somewhat earlier than in pressilabris. Modalities and timing of swarming are unknown.

Intra- and interspecific behaviour
F. foreli is very aggressive and territorial against other territorial Formica species and Lasius.

Food sources
Workers of a large polycalic colony at the margin of a light forest in Brandenburg visited in large files Aphidae on Pinus silvestris and Betula pendula trees.

Nomenclature

 *  foreli. Formica foreli Bondroit, 1918: 65 (w.q.m.) SWITZERLAND. [First available use of Formica exsecta subsp. pressilabris var. foreli Emery, 1909b: 192; unavailable name.] Combination in F. (Coptoformica): Müller, 1923: 146. Subspecies of pressilabris: Müller, 1923: 146. Revived status as species: Dlussky, 1964: 1033; Bernard, 1967: 324; Kutter, 1977c: 284. Junior synonym of pressilabris: Arakelian, 1994: 97; Seifert, 1994: 41. Revived status as species and senior synonym of goesswaldi, naefi, tamarae: Seifert, 2000a: 543.
 * naefi. Formica (Coptoformica) naefi Kutter, 1957: 4, figs. 1-6 (w.q.m.) SWITZERLAND. Junior synonym of foreli: Seifert, 2000a: 543. See also: Kutter, 1977c: 285.
 * tamarae. Formica (Coptoformica) tamarae Dlussky, 1964: 1033, figs. (w.q.m.) CAUCASUS. Junior synonym of pressilabris: Arakelian, 1994: 97; of foreli: Seifert, 2000a: 543.
 * goesswaldi. Formica (Coptoformica) goesswaldi Kutter, 1967a: 234, figs. 15-22 (w.q.m.) GERMANY. Junior synonym of foreli: Seifert, 2000a: 544. See also: Kutter, 1977c: 284.

Worker
Seifert (2000) - Rather small (CL 1288 ± 79, 1013-1472; CW 1219 ± 77, 981-1371). Head moderately elongated (CL/CW 1.057 ± 0.020, 0.991-1.120). Scape rather long (SL/CL 1.008 ± 0.023, 0.937-1.083). Clypeal setae restricted to anterior margin (Figs 3; 16), a small second level seta is in 7% of specimens present (ClySet 1.08 ± 0.27, 1-2). Clypeus lateral of the tentorial pit level only very exceptionally with single pubescence hairs surpassing the anterior margin by more than 10 μm (ClyPub 0.04 ± 0.23, 0-2.0, Fig. 16). Lateral semierect setae in the ocellar triangle always absent (OceSet 0%). Eye hairs fully absent or few minute hairs present (EyeHL 5.0 ± 2.1, 0-11; Fig. 9). Pubescence hairs in the occellar triangle dense (sqrtPDF 4.44 ± 0.44, 3.36-6.16; Figs 4; 13). Craniad profile of forecoxae without setae (nCOXA 0.0 ± 0.0). Lateral metapleuron and ventrolateral propodeum without standing setae (nMET 0.0 ± 0.0). Outer edge of the hind tibial flexor side with few semierect first order setae, second order setae absent (nHTFL 2.67 ± 1.16, 0-6.0). Erect setae on gaster often beginning on posterior margin of fourth tergite (TERG 3.88 ± 0.40, 3-5). Pubescence on first gaster tergite variable, but usually relatively dense (sqrtPDG 6.09 ± 0.44, 4.55-7.34).

Queen
Significantly larger than Formica pressilabris (CL 1341 ± 38, 1279-1464; CW 1362 ± 38, 1286-1479; ML 2227 ± 57, 2107-2415). Head proportions of average Coptoformica type (CL/CW 0.985 ± 0.022, 0.934-1.042), scape longer than in pressilabris (SL/CL 0.910 ± 0.023, 0.857-0.962). Clypeal setae restricted to anterior margin, second level setae only exceptionally present (ClySet 1.01 ± 0.12, 1-2). Clypeus lateral of the tentorial pit level without pubescence hairs surpassing the anterior margin by more than 10 μm (ClyPub 0.0 ± 0). Erect setae in the ocellar triangle absent. Eye hairs absent or short (EyeHL 6.1 ± 3.6, 0-21). Pubescence in the occellar triangle very dense (sqrtPDF 4.03 ± 0.32, 3.36-4.77). Occipital corners of head with fully appressed pubescence (OccHD 0.0 ± 0.0). Dorsal head surface variable, on average less shining than in pressilabris (GLANZ 1.87 ± 0.35, 1.0-2.5). Craniad profile of forecoxae without setae (nCOXA 0.0 ± 0.0). Dorsal mesosonotum and scutellum without standing setae and only appressed pubescence (MnHL 0.0 ± 0.0). Outer edge of the hind tibial flexor side with very few suberect to subdecumbent first order setae, second order setae absent (nHTFL 1.23 ± 0.62 0-2.5). Erect setae on gaster tergites usually beginning at the posterior margins of fourth to fifth tergite (TERG 4.65 ± 0.56, 2-5). Pubescence on first gaster tergite usually dense (sqrtPDG 5.42 ± 0.54, 4.54-6.68). Whole body less shining than in pressilabris.

Type Material
Formica exsecta pressilabris var. foreli. Vaux near Morges, Switzerland, leg. Forel. Holotype worker [investigated].

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