Lasius alienus

Common in Europe and Asia, where its preferred habitats are open areas such as agricultural fields.

Identification
Greyish yellow to brownish black. Pubescence adpressed, moderately thick over whole body and appendages. Short erect hairs scattered over dorsum and round whole occipital margin of head. Back of head convex. Ocelli indistinct or invisible; frontal furrow indistinct. Erect hairs absent on scape and front tibiae, sometimes present on hind tibiae. Length: 3.0-4.2 mm (Collingwood 1979).

Distribution
This species occurs throughout Europe and Asia, from the British Isles and Scandinavia south to Morocco and Tunisia, east into Lebanon, northern Iraq, and southern China, and north into Russia, Central Asia, China, and Japan (Ellison et al., 2012). This name had long been applied to a morphologically similar North American form, but this ant is now Lasius americanus (Schär et al. 2018).

Distribution based on Regional Taxon Lists
Oriental Region: India, Pakistan. Palaearctic Region: Albania, Andorra, Armenia, Austria, Belarus, Belgium, Bulgaria, Channel Islands, China, Czech Republic, Denmark, Estonia, Finland, France, Georgia, Germany, Greece, Hungary, Iberian Peninsula, Iran, Israel, Italy, Japan, Kazakhstan, Kyrgyzstan, Latvia, Lithuania, Malta, Mongolia, Montenegro, Netherlands, Poland, Portugal, Republic of Korea, Republic of Macedonia, Republic of Moldova, Romania, Russian Federation, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey, Turkmenistan, United Kingdom of Great Britain and Northern Ireland.

Biology
Wilson (1955) - In North Africa and France (Bernard, 1950; Scherdlin, 1909), Ireland (O’Rourke, 1950), England (Diver, 1940), Germany (Gosswald, 1932), East Prussia (Skwarra, 1929), and Daghestan (Kuznetzov-Ugamskij, 1929), Lasius alienus typically inhabits open dry situations, nesting under stones and occasionally constructing crater entrances in open soil. It shows much less latitude in nesting sites than its sister species Lasius niger, but is more successful in cultivated areas. Bernard notes that in France it is able to replace niger entirely in pastures, even at high elevations, but tends to give way in turn to Tapinoma simrothi and Tapinoma nigerrimum. Diver, in an intensive study of the comparative ecology of alienus and niger in a local area in Dorset, found alienus restricted mostly to dry heath, whereas niger occurred in every major habitat studied. In Daghestan, Kutznezov-Ugamskij found alienus to have more southern affinities than niger. Where the two occur together, alienus is limited mostly to the steppes and mountain meadows (up to 11,000 feet), while niger occurs mostly in the forests.

In Eurasia alienus is replaced in most habitats, including woodland, by its extremely successful and abundant sister species Lasius niger.

Lasius alienus probably does not differ much from niger in food habits and ethology. Several Europeans, including Gosswald and O'Rourke have independently observed that alienus tends to be the more secretive of the two species. This is possibly correlated with the preference of this species in Eurasia for more exposed situations.

Records of nuptial flights in this species are too sparse to allow a rigorous comparison with niger. In Europe winged forms are found in nido during about the same period as for niger. I have records ranging from June (Trieste, MCZ; no further date) to October 28 (Italy, MCZ) without evident preponderance during any part of this period; a single pair were preserved in copula in October (Trieste; MCZ; no further date).

Europe
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.

Collingwood (1979) - This wide ranging species nests in the soil on sandy lowland heaths, dry open pasture, sea cliffs and rocky outcrops in North Europe. Its habits are mainly subterranean, feeding on the exudates of root aphids but also by scavenging and predating small insects. Workers are generally unobtrusive and non aggressive compared with Lasius niger. Nests are single queened founded by solitary fertilised queens. Mating swarms occur in August.

Other Insects
This ant has been associated with the butterflies and a species that has recently been split into two species: Polyommatus icarus and Polyommatus celin (Obregon et al. 2015).

Nomenclature

 *  alienus. Formica aliena Foerster, 1850a: 36 (w.m.) GERMANY.
 * Foerster, 1850a: 71 (q.); Wheeler, G.C. & Wheeler, J. 1953c: 147 (l.); Hauschteck, 1962: 219 (k.).
 * Combination in Lasius: Mayr, 1861: 49 (in key);
 * Combination in Lasius (Lasius): Ruzsky, 1912: 633; Forel, 1915d: 53; Wheeler, W.M. 1916k: 172; Karavaiev, 1936: 205;
 * Combination in Donisthorpea: Donisthorpe, 1915d: 212;
 * Combination in Formicina (Donisthorpea): Emery, 1916b: 240;
 * Combination in Formicina: Bondroit, 1918: 25;
 * Combination in Lasius (Donisthorpea): Nadig, 1918: 340;
 * Combination in Acanthomyops: Ruzsky, 1925b: 44;
 * Combination in Acanthomyops (Donisthorpea): Betrem, 1926: 215; Donisthorpe, 1927a: 8; Donisthorpe, 1950e: 1063;
 * Combination in Lasius: Ruzsky, 1916: 5; Wheeler, W.M. 1917i: 463; Menozzi, 1921: 32; Müller, 1923b: 125; Emery, 1925b: 230; Kuznetsov-Ugamsky, 1929a: 27.
 * Combination in Lasius (Lasius): Wilson, 1955a: 77.
 * Subspecies of niger: Forel, 1874: 46 (in key); Mayr, 1877: 20 (in list); Emery & Forel, 1879: 452; Mayr, 1886d: 429; Forel, 1886e: clxvii; Provancher, 1887: 236 (in key); Cresson, 1887: 255; Forel, 1889: 256; Forel, 1890a: lxvii; Emery, 1891b: 16; Forel, 1892i: 307; Lameere, 1892: 64; Emery, in Dalla Torre, 1893: 187 (footnote); Forel, 1894c: 404; Forel, 1894d: 12; Ruzsky, 1896: 71; Saunders, E. 1896: 25; Ruzsky, 1902a: 233; Ruzsky, 1903b: 306; Forel, 1904b: 386; Ruzsky, 1905b: 304; Wheeler, W.M. 1906c: 322; Forel, 1906b: 85; Forel, 1906c: 189; Wasmann, 1906: 114 (in key); Forel, 1909c: 105; Yano, 1910: 421; Bondroit, 1910: 485; Forel, 1910a: 23; Karavaiev, 1910a: 268; Forel, 1911d: 352; Karavaiev, 1912b: 588; Krausse, 1912b: 165; Forel, 1913d: 438; Ruzsky, 1914a: 61; Stitz, 1914: 84; Emery, 1914d: 159; Ruzsky, 1915a: 434; Forel, 1915d: 53 (in key); Emery, 1916b: 240; Ruzsky, 1916: 5; Wheeler, W.M. 1916k: 172; Escherich, 1917: 332 (in key); Wheeler, W.M. 1917a: 525; Wheeler, W.M. 1917i: 463; Nadig, 1918: 340; Santschi, 1919e: 246; Menozzi, 1921: 32; Menozzi, 1922b: 331; Soudek, 1922: 69; Kulmatycki, 1922: 80; Finzi, 1923: 4; Kuznetsov-Ugamsky, 1923: 243; Emery, 1925b: 230; Ruzsky, 1925a: 288; Ruzsky, 1925b: 44; Santschi, 1925g: 349; Soudek, 1925b: 16; Santschi, 1926f: 289; Menozzi, 1926b: 182; Karavaiev, 1927a: 300; Karavaiev, 1927c: 280 (in key); Karavaiev, 1927d: 347; Kuznetsov-Ugamsky, 1927e: 188; Menozzi, 1927b: 91; Kuznetsov-Ugamsky, 1928b: 20; Lomnicki, 1928: 8; Wheeler, W.M. 1928c: 38; Kuznetsov-Ugamsky, 1929a: 27; Kuznetsov-Ugamsky, 1929b: 37; Karavaiev, 1930b: 147; Wheeler, W.M. 1930h: 80; Karavaiev, 1931e: 214; Soudek, 1931: 13; Gösswald, 1932: 57; Menozzi, 1932b: 311; Wheeler, W.M. 1932a: 16; Arnol’di, 1933b: 603 (in key); Grandi, 1935: 103; Karavaiev, 1935b: 108; Menozzi, 1936d: 305; Karavaiev, 1936: 205 (redescription); Karavaiev, 1937: 175; Menozzi, 1939a: 312; Morisita, 1945: 22; Ruzsky, 1946: 69; Azuma, 1951: 88; Smith, M.R. 1951a: 850; Chapman & Capco, 1951: 202; Azuma, 1953: 4; Azuma, 1955: 80; Ceballos, 1956: 316.
 * Status as species: Schenck, 1852: 51; Mayr, 1855: 360 (redescription); Nylander, 1856b: 68; Gredler, 1858: 13; Smith, F. 1858b: 7; Mayr, 1861: 49 (in key); Roger, 1861b: 165; Roger, 1863b: 11; Mayr, 1863: 425; Smith, F. 1871b: 2; André, 1874: 180 (in key); Mayr, 1877: 6; Emery, 1878b: 47; Saunders, E. 1880: 209; Mayr, 1880: 26; André, 1882b: 192 (in key); White, W.F. 1884: 255; Nasonov, 1889: 22; Emery, 1891b: 16; Dalla Torre, 1893: 181; Emery, 1897f: 238; Ruzsky, 1902d: 16; Ruzsky, 1903c: 207; Bingham, 1903: 342; Viehmeyer, 1906: 56; Emery, 1908d: 24; Bondroit, 1911: 11; Donisthorpe, 1915d: 212; Bondroit, 1918: 25; Crawley, 1920b: 177; Müller, 1923a: 74; Müller, 1923b: 125; Lomnicki, 1925b: 3; Betrem, 1926: 215; Stärcke, 1926: 124 (in key); Donisthorpe, 1927a: 8; Donisthorpe, 1927b: 242; Finzi, 1933: 165; Stitz, 1934: 9; Zimmermann, 1935: 48; Ruzsky, 1936: 90; Finzi, 1939c: 160; Stitz, 1939: 279; Novák & Sadil, 1941: 101 (in key); Röszler, 1942a: 53; Stärcke, 1944a: 153; van Boven, 1947: 186 (in key); Arnol'di, 1948: 212 (in list); Creighton, 1950a: 419; Röszler, 1951: 91; Consani & Zangheri, 1952: 44; Wilson, 1955a: 77 (redescription); Bernard, 1956b: 261; Bernard, 1959: 351; Dlussky, 1962: 182; Baroni Urbani, 1964a: 7; Baroni Urbani, 1964b: 63; Baroni Urbani, 1964c: 166; Cagniant, 1964: 92; Cagniant, 1966b: 281; Bernard, 1967: 356 (redescription); Baroni Urbani, 1968b: 488; Cagniant, 1968a: 146; Kutter, 1968a: 61; Baroni Urbani, 1969a: 334; Collingwood & Yarrow, 1969: 79; Pisarski, 1969a: 231; Pisarski, 1969b: 306; Dlussky & Pisarski, 1970: 87; Cagniant, 1970c: 38; Baroni Urbani, 1971c: 200; Bourne, 1973: 24; Pisarski, 1975: 34; Tarbinsky, 1976: 138 (redescription); Collingwood, 1976: 305; Aktaç, 1977: 126; Azuma, 1977: 117; van Boven, 1977: 144; Kutter, 1977c: 227; Arnol’di & Dlussky, 1978: 555 (in key); Collingwood, 1978: 89 (in key); Wheeler, G.C. & Wheeler, J. 1978: 393; Smith, D.R. 1979: 1435; Collingwood, 1979: 97; Yamauchi, 1979: 156; Pisarski & Krzysztofiak, 1981: 160; Schembri & Collingwood, 1981: 438; Collingwood, 1981: 27; Allred, 1982: 479; Collingwood, 1982: 285; Wheeler, G.C. & Wheeler, J. 1986g: 65; Agosti & Collingwood, 1987b: 282 (in key); Nilsson & Douwes, 1987: 70; DuBois & LaBerge, 1988: 149; Deyrup, et al. 1989: 99; Kupyanskaya, 1990: 218; Dlussky, Soyunov & Zabelin, 1990: 159; Casevitz-Weulersse, 1990c: 428; Morisita, et al. 1991: 27; Wu, J. & Wang, 1992: 1312; Atanassov & Dlussky, 1992: 237; Seifert, 1992b: 13 (redescription); Arakelian, 1994: 116; Radchenko, 1994b: 115 (in key); Douwes, 1995: 94; Bolton, 1995b: 221; Wu, J. & Wang, 1995: 155; Tang, Li, et al. 1995: 108; Collingwood & Prince, 1998: 23 (in key); Czechowski, et al. 2002: 105; Mackay & Mackay, 2002: 379; Deyrup, 2003: 45; Imai, et al. 2003: 63; Coovert, 2005: 120; Csösz, & Markó, 2005: 230; Karaman, G.S. & Karaman, 2005: 56; MacGown & Forster, 2005: 64; Bračko, 2006: 148; Bračko, 2007: 20; Seifert, 2007: 272; Werner & Wiezik, 2007: 153; Zryanin & Zryanina, 2007: 234; Gratiashvili & Barjadze, 2008: 136; Casevitz-Weulersse & Galkowsky, 2009: 483; Lapeva-Gjonova, et al. 2010: 35; Boer, 2010: 42; Csösz, et al. 2011: 58; Legakis, 2011: 26; Borowiec, L. & Salata, 2012: 498; Czechowski, et al. 2012: 263; Ellison, et al. 2012: 189; Borowiec, L. 2014: 83; Seifert & Galkowski, 2016: 52 (in key); Radchenko, 2016: 362; Deyrup, 2017: 206; Schar et al., 2018: 6.
 * Senior synonym of pannonica: Wilson, 1955a: 77; Radchenko, 2016: 362.
 * Material of the unavailable names alienoamericanus, flavidus, turkmenus referred here by Wilson, 1955a: 77.

Type Material
Wilson (1955) - Dr. H. Bischoff has informed me that no syntypes of Lasius alienus can be located in the Foerster Collection in the Berlin Museum. What may be part of the type series has been found instead in the Mayr Collection and lent me by Dr. M. Beier. This consists of two pins, one holding two workers and the other a single male, labelled "Aach. Forst/Las. alienus det. Mayr." The workers are identifiable as typical alienus.

Worker
Wilson (1955) - Within the PW range of 0.53-0.70 mm., the seta count is always less than 20 and usually less than 10. The seta count is strongly allometric, making it advisable to determine individual specimens by comparing them with the regression zones of Figure 6. In Europe the regression zones of Lasius niger and Lasius alienus are parallel but well segregated; the alienus line is set so that the great majority of workers have seta counts of less than 5, while most niger exceed 20. In eastern Asia, on the other hand, alienus evidently becomes scarcer, and the niger zone shifts down and forward to become contiguous with that of alienus. As a result, a small number of individuals cannot be safely determined to either species.

Size ranging and averaging smaller than in niger. In a sample of 147, with no more than 2 per nest series, mean with standard error 0.56 ± 0.004 mm., standard deviation 0.054 mm, Color averaging lighter than niger, although total variation in both species shows complete overlap.

Queen
Wilson (1955) - Seta count never exceeding 10 and usually 0.

Size averaging smaller than niger when the North American populations are included.

Male
Wilson (1955) - Seta count almost always 0.

Size range about the same as in Lasius niger and showing parallel geographic variation. Mandibles typically of niger type, but in two series (Engadin, Switzerland, Kutter leg. and Coll., Hornet, Beltrami Co., Minn., A. Achenbach leg., G. C. Wheeler Coll.) the mandible type is closer to the intermediate type of Lasius brunneus. Subgenital plate showing the same wide variation as in Lasius niger; series from Godinne, Belgium (A. Raignier leg.; MCZ) and the Engadin Valley, Switzerland (Kutter) encompass within themselves the full variation from the unilobed to bilobed condition.