Formica pressilabris

A mound building Coptoformica species that inhabits open sites and can form networks of nest mounds that number in the hundreds.

Identification
Bicoloured; head and scale deeply excised. Eyes bare. Maxillary palps very short, 5 or 6 segmented. Erect hairs on dorsum restricted to anterior margin of clypeus and gaster tergites 4 to apex. Clypeus transversely impressed below mid line, with a distinct concavity when seen in profile. Gaster pubescence sparse with hairs slightly shorter than their interspace - general appearance moderately shining. Length: 4.2-6.0 mm (Collingwood 1979).

Seifert (2000) - Males: Hairs on eyes fully absent or very sparse; EyeHL 0-12 μm. ClySet 1. Mesosoma with nearly appressed pubescence and without semierect setae. Craniad profile of forecoxae without standing setae. Pubescence in the ocellar triangle dilute; sqrtPDF 3.7-5.1. Scape short; SL/CS 0.860 ± 0.036.

Distribution
Seifert (2000) - Formica pressilabris represents a boreo-alpinecontinental species. The boreal range goes north to 65°N in Fennoscandia and reaches with an atlantic extension Denmark and the Netherlands. The continental range (which is fully connected with the boreal range in S Finland and the E Baltic) goes west to central Poland and W Slovakia. The are no recent records from Germany and the species is most probably extinct. A sample with two workers and a male collected by M. Zwecker in the vicinity of Würzburg / N Bavaria in 1929 indicates that isolated relict populations may have survived outside the main ranges. The most eastern samples of pressilabris investigated come from Lake Baikal (105°E, 52°N) and S Tibet (exact locality not known; approximately 92°E, 28°N, elevation > 4000 m; German Tibet Expedition 1938/39; samples 13a-c and 14a-d). The alpine population is distributed in the Swiss, French, and Italian Alps at 1802 ± 200 m (1460-2250, n = 41; with 28 sites at 1750-2250 m).

Distribution based on Regional Taxon Lists
Palaearctic Region: Albania, Andorra, Armenia, Austria, Belarus, Belgium, Bulgaria, Czech Republic, Denmark, Estonia, Finland, France, Germany, Hungary, Iberian Peninsula, Latvia, Lithuania, Luxembourg, Mongolia, Netherlands, Norway, Poland, Romania, Russian Federation, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey, Ukraine.

Habitat
Seifert (2000) - In all parts of its geographic range, within the boreo-continental or the alpine range, nests of pressilabris are found in semidry to fresh oligotrophic grassland. These are either pastures, alpine meadows, clearings within woodland, or continental steppes.

Biology
Collingwood (1979) - This species constructs football size mounds of grass litter in dry pasture and on banks in open woodland. Usually two or more nests are found together with up to two thousand workers and several queens in each. In Poland F. pressilabris has been extensively studied by Czechowski (1975); there the species is mainly found in open meadows in polygynous polycalic colonies of many nests. The chief food source was the exudate of species of aphids feeding on herbage and very little predatory activity was observed. In Fennoscandia nests observed have usually been either single or more commonly in groups of up to five. Although similar in appearance to Formica forsslundi this is a dry habitat species and does not normally occur in the neighbourhood of mires. Alatae occur in July and August.

Seifert (2000):

Status as threatened species
The population in the W Alps is obviously stable, though mechanical stress by intensive cattle pasturing and alpine sports can clearly reduce populations. The Dutch, Danish, Polish, and Slovakian populations are probably much more threatened but exact data are not available. Germany: Red List 0 (extinct), Switzerland: Red List 3 (threatened).

Colony foundation
There is very sparse direct evidence which Serviformica species is used for socially parasitic colony foundation; in the alpine range, Formica lemani is most certainly the major host. One nest sample from the Klausenpass / Switzerland (in coll. H. Kutter) still contained several lemani workers. Monodomous nests seem to be more frequent in continental Russia and polygynous/polycalic colonies are more abundant in Central Europe. Polycalic colonies may have very instable nest positions in habitats with recource limitation.

Nest construction
Mound construction is not fundamentally different from the normal Coptoformica type. Mound material may also include seeds, soil particles and tiny pebbles. The mounds are smaller than in Formica exsecta and their diameter is normally < 40 cm. An exceptionally large polygynous nest observed in the Bieszczady Mountains (Czechowski 1975) had a diameter of 100 cm and must have contained several hundred queens. A nest excavated by Dlussky near Voronesh showed galleries mainly to a depth of 50 cm, but a vertical duct led to chambers in a depth of 110 cm which were probably used during hibernation or excessive summer drought. On Swiss mountain pastures with intensive cattle grazing and condensed soil, the epigaeic nest parts can be small and the subterranean parts are mainly excavated in the very solid root turf that gives some protection against mechanical damage. In the Bieszczady Mountains, nests were frequently found in deserted or poorly inhabited earth mounds of Lasius flavus.

Demography of nests and colonies
Polycalic colonies may comprise > 100 nests/2000 m2 and two colonies mapped by Czechowski (1975) contained 74 nests/1250 m2 and 60 nests/580 m2. An exact census of nest populations has not been performed but the situation seems similar to Formica bruni or Formica foreli. According to Pamilo & Rosengren (1984), monodomous populations are monogynous, have a sex ratio of < = 1 : 1, and have mainly macraners. Polydomous populations are polygynous with related gynes, have a sex ratio > 1, and have mainly micraners. Diploid males were found in polydomous pressilabris colonies.

Swarming
With respect to the whole geographic range, alates are found in the nests July 31 ± 15.1 d (June 25-September 5, n = 16). In the Alps, the majority of alates occurs in the period July 17-August 5. In polycalic colonies of the Swiss Alps about 90% of females fly, the others are inseminated at the nest mounds (Schneider pers. comm.). Schneider also discovered a mating place near Montana/Swiss Alps at 2100 m which was situated inside the territory of a polycalic colony. About 15 queens were waiting in tall grasses on the upper edge of a small grassy slope bordering a small grassy plateau. The males patrolled at the top level of grasses in the lee position of queens, apparently for a better perception of queen sex pheromones.

Intra- and interspecific behaviour
Polycalic colonies frequently exchange populations and show no aggressivity to members of distant polygynous nests of the same colony.

Food sources
The main energy supply is provided by trophobiosis with any suitable species of Aphidae while predatory activity is usually less important. Aphid colonies are guarded and adult beetles of Coccinella septempunctata are attacked by the ants. Large aphid colonies at lower sprouts of plants can be sheltered by thin walls of plant material.

Fungi
This species is a host for the ectoparastic fungus Aegeritella tuberculata (Espadaler & Santamaria, 2012).

Nomenclature

 *  pressilabris. Formica pressilabris Nylander, 1846a: 911, pl. 18, fig. 21 (w.q.m.) FINLAND. Combination in F. (Coptoformica): Müller, 1923: 146. Subspecies of exsecta: Forel, 1874: 51; Emery & Forel, 1879: 450; Ruzsky, 1904b: 5; Emery, 1909b: 191; Wheeler, W.M. 1913f: 491; Forel, 1915d: 59; Emery, 1916b: 257; Ruzsky, 1925b: 43; Emery, 1925b: 257; Karavaiev, 1929b: 217; Karavaiev, 1936: 255; Stitz, 1939: 312. Status as species: André, 1882b: 179; Ruzsky, 1895: 12; Bondroit, 1912: 352; Bondroit, 1918: 64; Kutter, 1957: 11; Bernard, 1967: 324; Dlussky, 1964: 1032; Dlussky, 1967a: 103; Dlussky & Pisarski, 1971: 201; Kutter, 1977c: 285; Collingwood, 1979: 132; Atanassov & Dlussky, 1992: 285; Seifert, 2000a: 541. Senior synonym of rufomaculata: Seifert, 2000a: 541. See also: Radchenko, 2007: 36.
 * rufomaculata. Formica exsecta var. rufomaculata Ruzsky, 1895: 13 (w.) RUSSIA. [Also described as new by Ruzsky, 1896: 68.] Subspecies of pressilabris: Ruzsky, 1902e: 16. Raised to species: Dlussky, 1964: 1035. Junior synonym of pressilabris: Seifert, 2000a: 541. See also: Dlussky, 1967a: 108; Arnol'di & Dlussky, 1978: 552; Kupyanskaya, 1990: 203.

Worker
Seifert (2000) - Rather small (CL 1280 ± 73, 1046-1430; CW 1221 ± 70, 1000-1371). Head shape of average Coptoformica type (CL/CW 1.049 ± 0.020, 0.987-1.157). Scape short (SL/CL 0.974 ± 0.022, 0.914-1.031). Clypeal setae restricted to anterior margin (Fig. 3), a second level seta in only 3% of specimens present (ClySet 1.03 ± 0.17,1-2). Clypeus lateral of the tentorial pit level only very exceptionally with single pubescence hairs surpassing the anterior margin by more than 10 μm (ClyPub 0.02 ± 0.16,0-1.5). Lateral semierect setae in the ocellar triangle always absent (OceSet 0%). Eye hairs fully absent or few minute hairs present (EyeHL 4.6 ± 1.9, 0-9). Pubescence hairs in the occellar triangle sparse (Figs 4; 14; sqrtPDF 6.28 ± 0.57, 4.56-7.88). 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 (Fig. 2, nHTFL 2.77 ± 1.20, 0-6.5). Erect setae on gaster often beginning on posterior margin of third tergite (TERG 3.16 ± 0.48, 2-4). Pubescence on first gaster tergite relatively sparse (sqrtPDG 6.68 ± 0.39, 5.79-7.86).

Queen
Seifert (2000) - Size small (CL 1280 ± 39, 1189-1354; CW 1293 ± 33, 1197-1369; ML 2032 ± 67, 1843-2192). Head proportions without peculiarities (CL/CW 0.990 ± 0.020, 0.950-1.031), scape very short (SL/CL 0.849 ± 0.019, 0.822-0.892). Clypeal setae restricted to anterior margin (ClySet 1.02 ± 0.12, 1-2). Clypeus lateral of the tentorial pit level without pubescence hairs surpassing the anterior margin by more than 10 μm. Erect setae in the ocellar triangle absent. Eye hairs fully absent or very minute (EyeHL 4.5 ± 1.8, 0-8). Pubescence in the occellar triangle very sparse (sqrtPDF 6.09 ± 0.75, 4.49-7.85). Occipital corners of head with fully appressed pubescence (OccHD 0.0 ± 0.0). Dorsal head surface shining (GLANZ 2.56 ± 0.42, 1.5-3.0). Craniad profile of forecoxae without setae (nCOXA 0.0 ± 0.0). Dorsal mesosoma without standing setae (MnHL 0.0 ± 0.0), only with appressed, dilute pubescence. Outer edge of the hind tibial flexor side with very few suberect to subdecumbent first order setae, second order setae absent (nHTFL 1.31 ± 0.698, 0-3.5). Erect setae on gaster tergites beginning at the posterior margins of third to fifth tergite (TERG 3.77 ± 0.53, 3-5). Pubescence on first gaster tergite sparse (sqrtPDG 7.37 ± 0.66, 5.48-8.60). Whole body smooth and shining.

Type Material
Seifert (2000) - Helsingfors, Finland. Lectotype by present designation 1 worker; paralectotypes 3 _ _, 5 workers [investigated].