Formica selysi

This ant has been associated with the butterfly Glaucopsyche alexis (Obregon et al. 2015). It hybridizes with Formica cinerea in the Rhône valley in Switzerland, where they form a mosaic hybrid zone, with limited introgression from F. selysi into F. cinerea (Blacher et al., 2022).

Identification
Seifert (2002) - A member of the Formica cinerea group. Formica selysi cannot be confused because of its extreme pilosity. In the worker, nest sample means of nHFEX range 7.0 - 44.0 while the upper extreme known in 125 samples of other species is 2.5. Similar is the situation in nHT. Gynes are as easily identified: individual values of nHFEX range 11 - 47 and those of nHT 5-22.

Distribution
Seifert (2002) - The known geographic range of Formica selysi stretches from the Pyrenees (1.26 W) across S France to the Alps (11.51 E) and from the N. Apennine (44.20 N) to the Vosges (48.14 N). According to Petrov & Collingwood (1993), the easternmost site known is Gorizia (45.57 N, 13.37 E).

Distribution based on Regional Taxon Lists
Palaearctic Region: Albania, Austria, France, Germany, Iberian Peninsula, Slovenia, Spain, Switzerland.

Biology
Seifert (2002) - F. selysi is abundant in the southern half of France and the western Alps. Primary habitats are undoubtedly river banks. Artificial habitats such as stone or concrete constructions on river dams or along roads are also inhabited as well as pavement; and walls in the centre of cities (Brixen/ N. Italy, Hellrigl pers. comm.).

Concluded from observations in the Alps and northern Prealps, F. selysi is obviously better adapted to river sites with a higher velocity of flow and more frequent inundation than the competing Formica cinerea and Formica fuscocinerea (F. Bernard's name Formica torrentium suggests the same adaptation also in the Pyrenees). As result, F. selysi is more frequent on river banks with coarser material and it is often the eudominant ant species on isolated gravel islands within the river. In the Alps, F. selysi goes higher than F. fuscocinerea and F. cinerea, following the river banks up to 1780 m. Lude et al. (1996) and Lude etal. (1999) described adaptations of F. selysi to inundation and shifting of river bank material: 72 % of the nests survived inundations lasting for 9 - 43 hours and the ants could dig out through 10-20 cm of sand or gravel deposited on the nest entrances. If nest entrances were damaged, floating worker clusters with gynes and broods in the centre could be formed. After landing, the workers used their antennae and forelegs to save detached larvae or eggs from the water surface.

Nomenclature

 *  selysi. Formica cinerea var. selysi Bondroit, 1918: 54 (w.) FRANCE. Combination in F. (Serviformica): Emery, 1925b: 246. Raised to species: Kutter, 1977c: 253. Senior synonym of torrentium: Seifert, 2002b: 259.
 * torrentium. Formica torrentium Bernard, 1967: 300 (w.q.m.) FRANCE. [Bernard, 1967: 300, indicates that Bernard, 1960: 108 contains the original description of torrentium. The name is not mentioned in the 1960 publication.] Junior synonym of selysi: Seifert, 2002b: 259.

Worker
Seifert (2002) - Medium-sized, mean CS 1368. Head moderately elongated, CL/CW(1400) 1.127. Scape of average length, SL/CS(1400) 1.052. Clypeus with a median keel, finely microreticulate, its anteriormost portion finely longitudinally microcarinulate. Frontal triangle finely transversally microcarinulate and with 40 - 50 short pubescence hairs. Eyes with few scattered microsetae of 4-7 mm length. Dorsal plane of scape without setae. Most hairy species of the group. All surfaces of head, mesosoma, petiole, gaster, coxae and legs strongly setose. In contrast to all other species, extensor side of femora with semierect setae. Nest sample means of setae numbers: genae 2.5 - 26.3, occipital margin in dorsal aspect 27.5 - 67.0, gula 18.0 - 59.3, propodeum 17.8 - 54.5, extensor profile of both hind femora 7.0 - 44.0, flexor profile of both hind femora 28.0 - 60.0; extensor profile of hind tibiae 5.5 - 18.5. In anterior view, number of setae surpassing petiolar scale margin above spiracular level 15.5 - 51.3. Transition between dorsal and caudal profiles of propodeum broadly convex. Petiole scale narrower than in other species, its dorsal crest in frontal view convex; petiole scale in lateral aspect thicker than in other species, with convex anterior and rather straight or slightly convex posterior profile and a rather blunt apex. Head, mesosoma, petiole, and gaster covered by a dense, appressed, silvery pubescence, PDG 7.0. The pubescence hairs on gaster tergites thicker than usual, having 3 - 4 mm diameter, which produces at lower magnifications a silvery surface impression. Colour of cuticula more superimposed by the silvery pubescence than in other species and less varying than in Formica cinerea. A frequent colouration is: vertex, mesosoma, petiole and gaster dark brown, coxae, appendages, lateral and anterior head medium or lighter brown. Lighter morphs with increased reddish colour component locally occurring (France: Massive Central, Switzerland: Wallis).

Type Material
Seifert (2002) - France: Alpes Maritimes: Saint Etienne de Tinee [types investigated]. Eight worker syntypes labelled St. Etienne de Tinee Alp. mar. \ 1150 m \ Formica v. selysi type Bondr.,.

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