Lasius emarginatus

A very common species occurring in central and southern Europe, and from Anatolia to the Caucasus, even in disturbed habitats (Rigato & Toni, 2011).

Identification
Distinguished in the worker caste by the distinctly red alitrunk, more sparse, oblique appendage hairs and relatively longer antennal scapes. The queen has the mesoscutum reddish and distinctly flattened. The male has the mesopleurae in part testaceous yellow, sparse scape hairs and a more sculptured frontal triangle than Lasius niger (Collingwood 1979).

As a member of the close-knit and difficult complex, Lasius emarainatus, like niger, must be determined by careful examination of multiple characters. It is easily separable from Lasius niger and Lasius alienus over part of its range on the basis of color and appendage length, but the three species tend to show convergent variation in the Balkans area, Mediterranean perimeter, and southcentral and eastern Asia. (Wilson 1955)

Distribution
This is a Central and South European species that occurs in Poland, and the Channel Islands (Collingwood 1979).

Distribution based on Regional Taxon Lists
Palaearctic Region: Albania, Andorra, Armenia, Austria, Azerbaijan, Balearic Islands, Belarus, Belgium, Bulgaria, Canary Islands, Channel Islands, China, Croatia, Czech Republic, France, Georgia, Germany, Gibraltar, Greece, Hungary, Iberian Peninsula, Iran, Israel, Italy, Luxembourg, Malta, Monaco, Montenegro, Poland, Portugal, Republic of Macedonia, Republic of Moldova, Romania, Russian Federation, Slovakia, Slovenia, Spain, Switzerland , Turkey, United Kingdom of Great Britain and Northern Ireland.

Biology
Wilson (1955) - This species nests mostly under rocks in open, dry situations. In Germany Gosswald (1932) found it in orchards, along forest borders, and in wasteland, nesting almost exclusively under rocks and in the crevices of rock walls, and avoiding woodland and moist situations in general. Nowotny (1931) found it uncommon in southwestern Poland, inhabiting dry areas under rocks and in walls. It was found in the same general type of habitat by Scherdlin (1909) in Alsace, by Donisthorpe (1928) in Italy, by Zimmermann (1934) in Yugoslavia, and by Goetsch (1937) in Italy, Switzerland, and Germany. Zimmermann found one colony in the wood of a pine stump on Campo Marzio in the Quarnerian Islands. Gosswald and Goetsch both report that the species occasionally enters houses.

Ecological data accompanying the Lebanon series previously mentioned are of interest because of the peripheral origin of these series (see under distribution). Dr. Christiansen collected the Wadi Jahhnam workers in a valley bottom well shaded by mixed conifers and maples. The ants were foraging above ground along a stream bank. The Kammouha Plain workers were taken well up on a mountainside (1900 meters) under rocks in spruce woods.

Food habits, pastoral activities, and colony founding in this species have been treated briefly by Goetsch (1937). They do not appear to differ fundamentally from Lasius niger and are not worth bringing into the discussion here.

Guiliani et al. (2019) observed this species foraging on extrafloral nectaries of the invasive Reynoutria x bohemica (Polygonaceae) in Tuscany. The habitats examined were river banks and disturbed habitats.

Nomenclature

 *  emarginatus. Formica emarginata Olivier, 1792: 494 (w.q.m.) FRANCE. Hauschteck, 1962: 219 (k.). Combination in Lasius: Fabricius, 1804: 416; in Formicina (Donisthorpea): Emery, 1916b: 240; in Lasius: Menozzi, 1921: 32; Müller, 1923: 123; in L. (Lasius): Wilson, 1955a: 89. Subspecies of niger: Forel, 1874: 46; Emery & Forel, 1879: 452; Ruzsky, 1905b: 302; Bondroit, 1910: 486; Stitz, 1914: 85. Status as species: André, 1882b: 193; Nasonov, 1889: 23; Ruzsky, 1902d: 16; Forel, 1915d: 53; Emery, 1916b: 240; Bondroit, 1918: 24; Müller, 1923: 123; Finzi, 1924a: 14; Karavaiev, 1927c: 279; Stitz, 1939: 283; Stärcke, 1944a: 155; Wilson, 1955a: 89; Bernard, 1967: 357; Kutter, 1977c: 228; Atanassov & Dlussky, 1992: 239; Seifert, 1992b: 34. Senior synonym of brunneoemarginatus, brunneoides, nigroemarginatus: Wilson, 1955a: 89; of illyricus, pontica: Seifert, 1992b: 34.
 * brunneoemarginatus. Lasius emarginatus var. brunneoemarginatus Forel, 1874: 47 (w.) SWITZERLAND. Junior synonym of emarginatus: Wilson, 1955a: 89.
 * brunneoides. Lasius niger var. brunneoides Forel, 1874: 47 (w.) SWITZERLAND. Junior synonym of emarginatus: Wilson, 1955a: 89.
 * pontica. Lasius alienus var. pontica Stärcke, 1944a: 157 (w.) CAUCASUS. Junior synonym of alienus: Wilson, 1955a: 78 [repeat of this synonymy in Arakelian, 1994: 117, is ignored]; of emarginatus: Seifert, 1992b: 34.

Worker
Wilson (1955) - (1) Scape and other appendages longer relative to body size than in all other members of the genus except Lasius productus. Eliminating the largest workers (HW 1.10 mm, or greater), the SI exceeds 103 in more than 95 per cent of nest series examined (Fig. 5); 95 per cent or more of Lasius niger and Lasius alienus in the same size range have an SI of less than 103, with the following exceptions: niger from the Balearics, North Africa, Canaries, and eastern Asia; and alienus from the Balkans and eastern Asia.

(2) As a corollary of (1), ML exceeding EW.

(3) Thoracic dorsum low and flattened with respect to the propodeum; if the heights of the propodeum and mesonotum are measured in profile from a base line drawn from the lowest point of the prosternum (anterior to the coxal insertion) to the lowest point of the mesosternum, the propodeum is usually about 1.05 X higher than the mesonotum; the two points are usually of equal height in niger and alienus.

(4) Scape with abundant standing hairs predominantly or entirely subdecumbent and tending to be concentrated on the distal third (Pl. 1, Fig. 8). Rarely the standing hairs may be predominantly suberect-erect or altogether lacking (see under further description below). niger, especially from eastern Asia, occasionally approaches this typical emarginatus condition.

(5) Coloration of medium and large workers (i.e. workers with PW about 0.53 mm. or greater) usually distinctive. Alitrunk and petiole yellowish red, contrasting with both the head, which is medium to dark brownish red, and the gaster, which is dark brownish red. The alitrunk and petiole occasionally darken to approach the niger-alienus coloration; this divergent condition appears to preponderate in the Balkans population.

In a sample of 75, with no more than 2 per nest series, PW range 0.48-0.78 mm., mean with standard error 0.633 -l- 0.006 mm., standard deviation 0.050 mm. Total range of SI 103-122, a strongly allometric character with highest values in the minimas. Head tends to be narrower than in niger and alienus, but considerable overlap occurs; in a limited series with HW range of 0.94-1.05 mm., CI varied between 84 and 91. Mandibular dentition similar to niger, with three or four basal teeth present, but differing statistically in two ways; (1) the four-toothed condition is more common, (2) the second tooth from the basal margin is often bifurcate, a condition rare in niger. Forty individuals each representing a different nest series were examined especially for dentition: 16 had three whole basal teeth, 16 had four whole basal teeth, and 8 had a bifurcate second tooth in a set of three. This variation is not allometric, since minimas may have four basal teeth, and it does not appear to have a rigid genetic control, since two adjacent conditions can occur in the same nest series and even on different mandibles of the same individual. The petiole is less variable in outline than in other species of the complex; in all series examined the dorsal margin was shallowly and angularly impressed.

Scape pilosity as described in the diagnosis with the following three exceptions: a series from Dalmatia (H. Kutter leg.; Oxford University Museum) has a preponderance of suberect-erect hairs along the plane of the seta count; two series from Lebanon (Kammouha Plain and Wadi Jahhnam; K. Christiansen leg.; MCZ) lack standing hairs altogether.

Queen
Wilson (1955) - (1) Within a HW range of 1.61-1.70 mm. in a limited number of series measured, SI ranged 76-86. If this is a general condition it allows a 90 per cent separation from sympatric series of niger, exclusive of the southern European and North African populations previously described.

(2) ML in this sample ranged 0.23-0.26 mm.

(3) Scape densely clothed with preponderantly subdecumbent and occasional decumbent hairs one-third to one-half as long as the maximum scape width.

(4) Alitrunk medium reddish brown, the head and gaster somewhat darker and tending to contrast against the alitrunk, but never so much as in the worker. This same coloration is closely approached by callow niger queens, so that separation on this character alone is difficult.

Several interesting character trends have been noted which are, however, of less than diagnostic value. The scutum in profile tends to be more flattened than in other members of the subgenus. The posterior 5/6 of the scutum may be perfectly flat, whereas in niger the anterior third or more is usually involved in the anterior declivity. The posterior scutal border (transscutal suture) was found to be markedly sinuate in five out of six specimens examined; in niger and other Lasius s. s. this border is rarely more than feebly sinuate and often perfectly straight. The punctures of the scutum tend to be deeper and more distinctive in emarginattts than in and alienus.

Male
Wilson (1955) - (1) Within a HW range of 0.92-1.07 mm. in a limited number of series measured, SI ranged 70-76.

(2) ML in this sample ranged 0.24-0.28 mm.

(3) Scape with numerous decumbent hairs one-fourth to one-half as long as the maximum scape width, and few or no suberect or erect hairs.

(4) Subgenital plate typically similar in outline to that of Lasius pallitarsis, but larger (in five nest series measured, maximum transverse length ranged 0.59-0.73 mm.), and more arc-shaped: the posterior border tends to be evenly concave, sweeping back evenly to the prominent posterolateral flanges, while the anterior border is correspondingly convex (one exception noted, see further description below).

Paramore length 0.24-0.27 mm. in all series examined, apparently varying allometrically with respect to head width to about the same degree as in niger. In the total of eight specimens (5 localities) examined for genitalic characters, the setiferous lobes of the subgenital plate showed the same amount and kind of variation as in niger (q.v.). Two males from the same nest series (Lausanne, Switzerland; M. Bibikoff leg. and Coll.) encompassed the total possible variation, one with a single lobe and the other with two lateral lobes. Seven of the specimens showed the diagnostic outline previously described; one from Milan (USNM) was sub quadrate and indistinguishable from sitkaensis except in size.