Formica corsica

A subalpine and mountain meadow inhabitant.

Identification
Seifert (2002) - A member of the Formica cinerea group. F. corsica has the weakest gular and occipital pilosity and the smallest body size of any species in the group and deviates strikingly from Formica cinerea in most of the setae characters. A conspecifity or close relatedness with Formica lemani, a species of the Formica fusca group with a habitat selection most similar to F. corsica, can be fully excluded since F. lemani shows nest sample means of nOcc and nPE of only 0.0 - 1.0, a shorter and denser gastral pubescence with much thinner hairs, a significantly shorter scape, much smaller eyes, and a much wider petiole scale with a sharper dorsal crest. F. corsica differs from the next similar species Formica fuscocinerea by nest samples means of nGU ranging in the interval [1.0, 3.3] (in F. fuscocinerea [3.7, 12.3]) and by a densely microcarinulate lateral mesonotum with an mean crest distance of 6 mm. The mean strength of carinulae is about 4 mm while the mean width of the smooth interspaces is only 2 mm - i.e. the ratio of sculptured surface to shining surface is about 2:1. In F. fuscocinerea this ratio is 1:4 or smaller and the microsculpture shows the form of a reticulum with elongated meshes. The occipital and propodeal pilosity of F. corsica is significantly weaker than in F. fuscocinerea but there is some overlap of sample means. Based upon (nest) sample means, F. corsica can be separated from F. fuscocinerea by a discriminant analysis.

Distribution
Corsica

Distribution based on Regional Taxon Lists
Palaearctic Region: France.

Biology
Seifert (2002) - The habitat selection of F. corsica deviates from that of related species. One should expect a member of the F. cinerea group to prefer xerothermous sand or gravel banks of rivers or lakes with sparsely developed field layer plants. However, according to Casevitz-Weulersse (pers. comm. 8 June 2001) and the labels of investigated samples, the main habitats of F. corsica are subalpine or mountain meadows between 1500 and 2400 m, including also moist grasslands at margins of glacier lakes. Casevitz-Weulersse emphasized that these ants have to live under conditions of hard and rather long winters, of extreme annual temperature amplitudes, rich precipitations of rain and snow, and violent winds. The activity period is restricted from June to September and the nests were found under stones or under bark. The unusual small size of the workers is possibly an expression of bad growth conditions or the increased need to use preformed microspaces for nesting. The specimens in the collection of F. Bernard, labelled Ajaccio, Tarunato, would indicate a site at altitudes below 1000 m. This site, however, should be confirmed by future investigations since the published and unpublished statements of Bernard are known to be full of mistakes.

Nomenclature

 *  corsica. Formica corsica Seifert, 2002b: 264, fig. 3 (w.) FRANCE (Corsica).

Worker
Smallest species within the F. cinerea group, CS 1200 ± 48. Head slightly more elongated than in F. fuscocinerea, CL/CW(1400) 1.139. Scape of average length, SL/CS(1400) 1.048. Clypeus in the anterior half and lateral comers densely longitudinally carinulate and with a median keel. Frontal triangle finely transversely microcarinulate and with about 25 short pubescence hairs. Eyes with few scattered microsetae of 3 - 4 mm length and large, EYE/CS in the holotype 0.310. Dorsal plane of scape and genae without setae. Least developed pilosity within the F. cinerea group: in the sample mean, occipital margin in dorsal aspect with only 6.0- 15.0 setae and gula with only 1.3-3.3 setae; extensor profile of both hind femora without, their flexor profile with 8 - 13.3 setae; extensor profile of hind tibiae without or occasionally with one small seta. In holotype, craniad surface of both procoxae with 19, pronotum with 37, mesonotum with 10, propodeum with 4, and petiole scale in anterior view with 4 setae. Lateral mesonotum anterior of metathoracic spiracle densely microcarinulate, with a mean carinular crest distance of 6 mm; mean strength of carinulae about 4 mm while the mean width of smooth interspaces only 2 mm - i.e. the ratio of sculptured surface against shining surface is about 2 : 1 and similar to the situation in F. cinerea. Dorsal and caudal profiles of propodeum forming a bluntly rounded angle of 150°. Petiole scale in frontal view rather narrow and with a rounded dorsal crest, in lateral aspect rather thick, wedge-shaped, and with convex anterior and posterior profiles. Head, mesosoma, petiole, and gaster blackish brown and covered by a dense silvery pubescence (PDF 10.0 and PDG 7.1 in the holotype).

Type Material
1st series, labelled CORSICA: Asco, 2000 m leg. A. Delestrade 1991.06.19 No 1514: Holotype and 2 paratypes in SMN Gorlitz, 3 paratypes MNHN Paris. 2nd series, labelled CORSICA: Niolo, 2000 m Mte Albanu leg. A. Delestrade 1992.09.13 No 1659: 4 paratypes MNHN Paris, 3 paratypes SMN Gorlitz. 3rd series, labelled CORSICA: Bavela, 1900 m leg. A. Delestrade 1991.09.21 No 1518: 6 paratypes MNHN Paris, 3 paratypes SMN Gorlitz. 4th series, labelled CORSE MONTEROTONDO 2400 m 7-VII-1974 J-P. HEBRARD REC.<<: 13 paratypes MNHN Paris, 3 paratypes SMN Gorlitz.