Formica forsslundi

Colonies are started by queens securing adoption with Formica transkaucasica. Nests are constructed of leaf litter usually on the margins of wet ditches or fringes of boggy lakes. Alatae have been found in the nests during July (Collingwood 1979).

Identification
Bicoloured, appearance shining, pubescence very sparse. Eyes bare. Erect hairs are present sparsely on clypeus, head, alitrunk and on gaster tergites 2 to apex. Maxillary palps very short - 5 segmented. Head and scale deeply excised. Length: 4.0-6.5 mm (Collingwood 1979).

Seifert (2000) - The description of Lohmander (1949) and its statements on the peculiar habitat selection and nesting should leave no doubt which species is meant. Males: Hairs on eyes absent or very sparse; EyeHL 0-20 μm. ClySet 1-2. Mesosoma with semierect pubescence and a number of semierect setae (difference to Formica pressilabris). Craniad profile of forecoxae with semierect pubescence and without or only single standing setae. Pubescence in the ocellar triangle and on second gaster tergite dilute; sqrtPDF 3.6-5.5, sqrtPDG 4.3-6.9. Scape short; SL/CS 0.882 ± 0.019.

Distribution
Seifert (2000) - A more or less coherent population is found in the subboreal European range, that spreads from N Germany (55°N) across Denmark to Fennoscandia north to 66°N. The Asian range is poorly known but there is no zoogeographic or biocenotic argument that the Siberian, Mongolian and Tibetian populations should not be connected with the W Palaearctic population accross the continous belt of subboreal biomes within the range of the abundant host species F. transkaucasica. A more southern range in the N Alps and SE Poland is documented by few, isolated bog populations between 47 and 51°N, which most certainly represent glacial relicts. In the Caucasus, an isolated subalpine population is found between 1500 and 2500 m. Such a subalpine population is also suspected to exist in the Alps between 1300 and 2200 m but the author could so far not see a voucher specimen.

Distribution based on Regional Taxon Lists
Oriental Region: Tibet. Palaearctic Region: Belarus, China, Denmark, Finland, Germany, Mongolia, Norway, Poland, Sweden, Switzerland.

Habitat
Seifert (2000) - In the European range, F. forsslundi represents a rather stenopotent species and is bound to different types of open bogs, wet heathland, or mesophilic sand dunes. In Fennoscandia, nests are preferentially situated on organic soil in wetter central and peripheral parts of peat bogs with different species of Ericaceae. Towards the south, more marginal Molinia stands on mineralic soil are preferred. In N Germany, a large population is found on semidry sand dunes with Deschampsia, Molinia, or Empetrum. The Caucasian population was found on subalpine to alpine pastures. In the cold steppes of Siberia, Mongolia and Tibet nest were found in xerothermous places on sandy soil with incomplete coverage of grasses but also in moister situations near to the ground water level.

Biology
Seifert (2000):

Status as threatened species
In Germany and Switzerland threatened by extinction (Red List 1). Protection of bogs and cautious habitat management in heathland or mesophilic sand dunes is critical for the survival of this species.

Colony foundation
Formica transkaucasica seems to be the exclusive host species of forsslundi throughout its whole range in Fennoscandia, Germany, Switzerland, the Caucasus, and Tibet. Nests in the wettest parts of peat bogs seem to be preferentially monogynous. Polycalic colonies were observed in the Caucasus and Poland but seem to be generally rare.

Nest construction
In wetter parts of peat bogs, nests are usually found in bults with the virtual nest being restricted to a deep central cylinder that is typically roofed by a cover of Ericaceae leaves or white Eriophorum wool. The bult margin contains no nest galeries and is normally penetrated by Ericaceae, Eriophorum, and other grasses. Sometimes skewed “solar collectors” are constructed with plant material. Nests on mineralic soil are usually of the normal Coptoformica type made with finely-cut grass pieces. These nests have average dimensions of 20 × 20 cm (height × diameter) with the largest nests measuring 20 × 40 cm. Sörensen (1993) noted rather instable nest positions in sand dune areas with an average of 25% abandoned nests per year. In a Swiss Molinietum, repeated mechanical stress by mowing has apparently caused a restriction of the nest galeries to subterranean parts (Agosti 1989). In Asia, simple soil nests without epigaeic mound constructions were observed in grasslands on sandy soil (Dlussky 1967) but the nest found by A. Gebauer in a moister site at Lake Koko Nur showed a typical mound construction with organic material.

Development and microclimatic requirements
Not studied. The nest spots in Europe indicate a higher tolerance against humidity compared to related species. The N German population started oviposition in mid April in the year 1998 (Soerensen pers. comm.).

Demography of nests and colonies
Only sparse information is available. Monogynous nests in bogs are not very populous: three nests excavated in Finland contained 500, 500, and 1500 workers. The largest population of forsslundi is known from the nature reserve Suederlueguemer Binnenduenen /N Germany with > 400 nests on 42 ha sand dune area and local densities of 84 nests/ha (Soerensen pers. comm.). No signs for polycaly (such as population exchange between the nests) were observed in this dense population.

Swarming
Not studied. Alates in the nests were found throughout the geographic range July 30.6 ± 9.9 d (July 15-August 25, n = 11).

Disjunct Population
The forsslundi population found on subalpine pastures of the Caucasus is most certainly fully isolated and shows an extremely short scape, no projecting pubescence hairs on lateral clypeus and reduced coxal pilosity. The extreme scape character in this population could be considered to justify erection of a new taxon. This is contradicted, however, by the high coincidence with the Palaearctic main population in the majority of characters and by the sharing of the same specific host species. The problem needs further investigation.

Nomenclature

 *  forsslundi. Formica (Coptoformica) forsslundi Lohmander, 1949: 163 (w.q.m.) SWEDEN. Senior synonym of strawinskii: Dlussky & Pisarski, 1971: 199; of brunneonitida, fossilabris: Seifert, 2000a: 552. See also: Kutter, 1977c: 285.
 * strawinskii. Formica forsslundi subsp. strawinskii Petal, 1963: 195, figs. 1a, 2a, 3, 4a, 5a, 6a, 7, 8a, 9a, 10a, 11 (w.q.m.) POLAND. Junior synonym of forsslundi: Dlussky & Pisarski, 1971: 199.
 * brunneonitida. Formica (Coptoformica) brunneonitida Dlussky, 1964: 1034, figs. (w.q.) MONGOLIA. Junior synonym of forsslundi: Seifert, 2000a: 552. See also: Dlussky, 1965a: 23.
 * fossilabris. Formica (Coptoformica) fossilabris Dlussky, 1965a: 25, fig. 16 (w.) TIBET. Junior synonym of forsslundi: Seifert, 2000a: 552.

Worker
Seifert (2000) - Rather small (CL 1281 ± 70, 1024-1404). Head shape of average Coptoformica type (CL/CW 1.051 ± 0.018, 1.007-1.099). Scape rather short (SL/CL 0.987 ± 0.019, 0.944-1.035); in the Caucasian population extremely short (SL/CL 0.947 ± 0.023, 0.912-0.979). Clypeus only in anterior area with standing setae, caudal setae always absent (ClySet 1.84 ± 0.52,1-3). Clypeus lateral of the tentorial pit level frequently with few pubescence hairs surpassing the anterior margin by more than > 10 μm; in the Caucasian population such hairs are fully absent; ClyPub 1.31 ± 1.21, 0-6.0. Lateral semierect setae in the ocellar triangle in many specimens absent (OceSet 47%). Eyes usually without or with few microscopically short hairs, in the Mongolian and Tibetian samples few longer hairs are frequently present; EyeHL 6.6 ± 3.2, 0-25. Pubescence hairs in the occellar triangle extremely sparse (sqrtPDF 6.96 ± 0.84, 5.63-9.80; Fig. 11). Craniad profile of forecoxae usually with single semierect setae which are in the Caucasian population fully absent; nCOXA 1.31 ± 1.35, 0-4.5. Lateral metapleuron and ventrolateral propodeum as a rule without standing setae (nMET 0.01 ± 0.05, 0-0.5). Outer edge of the hind tibial flexor side with several semierect first order setae, second order setae absent (Fig. 2, nHTFL 5.82 ± 1.14, 3.0-8.5). Erect setae on gaster tergites usually beginning on the first tergite (TERG 1.16 ± 0.40, 1-3). Pubescence on first gaster tergite variable but usually very sparse (sqrtPDG 7.09 ± 0.55, 5.62-8.24). Promesonotum frequently with a blackish patch with diffuse margin.

Queen
Size very small (CL 1223 ± 43, 1160-1307; CW 1248 ± 28, 1210-1299; ML 1885 ± 69, 1784-2003). Head proportions without peculiarities (CL/CW 0.980 ± 0.029, 0.911-1.022). Scape rather short (SL/CL 0.867 ± 0.019, 0.831-0.897), in the two Caucasian queens extremely short (SL/CL 0.796,0.797). Clypeal setae restricted to anterior portion, second level setae usually present. Erect setae in the ocellar triangle may be present. Eye hairs fully absent or very minute (EyeHL 6.2 ± 2.5, 0-10). Pubescence in the occellar triangle usually extremely sparse (sqrtPDF 5.95 ± 0.61, 4.80-6.96). Occipital corners of head with decumbent to appressed pubescence (OccHD 6.0 ± 6.4, 0-16). Dorsal head surface brilliantly shining (GLANZ 2.94 ± 0.16, 2.5-3.0). Craniad profile of forecoxae with few semierect setae, differentiation between setae and large pubescence hairs often difficult, making setae counts problematic (nCOXA 2.06 ± 2.54, 0-9.0). Dorsal mesosoma frequently with standing setae (MnHL 85.9 ± 54.1, 0-166). Outer edge of the hind tibial flexor side with several suberect to subdecumbent 1st order setae, second order setae absent (nHTFL 4.11 ± 1.89, 2.0-8.5). Erect setae on gaster tergites usually beginning on the first tergite (TERG 1.17 ± 0.38, 1-2). Pubescence on first gaster tergite sparse (sqrtPDG 6.73 ± 0.76, 5.06-8.07). Whole body smooth and shining, dark brown to blackish. Dorsal excision of petiole often deeply u-shaped.

Type Material
Seifert (2000) - Närke, Värmland, Västergötland, Sweden. No types available in the museums of Göteborg and Stockholm