Lasius alienus

Common in Europe and Asia, where its preferred habitats are open areas, and North America, where it is primarily a woodland species.

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).

Mackay and Mackay (2002) - This is a small, dark brown or black species with relatively large eyes (12-14 ommatidia in maximum diameter). The scape has few (less than 5) or no erect hairs (except at apex). The penultimate tooth is about the same size as the adjacent teeth (other 2 basal teeth).

Distribution
Lasius alienus has the widest distribution of all the members of the genus. In Eurasia it is found from the British Isles and southern Fennoscandia south to Morocco-Tunisia, east through Lebanon and Iraq to Kashmir and southern China, and north into European Russia, central Asia, China, and Japan. Unlike Lasius niger, it apparently does not occur in the Balearics, Canaries, and Azores, or in Formosa. In North America it is found from southern British Columbia to Nova Scotia and south to the mountains of Durango, Mexico, in the west, and to northern Florida in the east. (Wilson 1955).

Distribution based on Regional Taxon Lists
Nearctic Region: Canada, Canada, United States. Neotropical Region: Mexico. 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) - The Eurasian and North American populations differ markedly from one another in habitat preference. 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 North America Lasius alienus reverses this habitat preference. Over its entire range on this continent, it shows a strong predilection for well shaded woodland, where it nests in rotting logs and stumps and under stones. Among the hundreds of colonies I have encountered in the field in the eastern United States, nearly all conformed to this ecological character. It may happen, however, that at high elevations or at the northern periphery of its range, the species occasionally nests in open situations. At the summit of Grandfather Mountain in North Carolina, for instance, I found a small but vigorous population living under stones in an open blueberry-and-heath "bald". The elevation was 5800 feet, higher by 700 feet than any other collection of the genus made in the course of several field trips in the southern Appalachians.

I would like to venture the suggestion that the difference in habitat preferences between the Eurasian and North American populations may be a reflection of competition with various other members of the genus. In Eurasia alienus is replaced in most habitats, including woodland, by its extremely successful and abundant sister species Lasius niger. In North America it is replaced in nearly every available habitat except woodland by the equally successful and abundant members of the Lasius neoniger complex. As previously indicated in the description of the ecology of that species, Lasius pallitarsis occupies the same types of nesting sites as alienus and probably limits its northward spread. In general, one gains the impression that in Eurasia and North America alienus has been squeezed into relatively narrow ecological ranges by its congeneric competitors, but is nevertheless eminently successful within those ranges.

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). In North America records range from May 30 (Decatur Co., Ga.) to December 4 (Alachua Co., Fla.). Both of these are very exceptional dates, however; the majority of the other records fall in August.

Europe
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 Glaucopsyche alexis and a species that has recently been split into two species: Polyommatus icarus and Polyommatus celin (Obregon et al. 2015).

Fungi
This species is a host for the ectoparastic fungus Laboulbenia formicarum (Espadaler & Santamaria, 2012).

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 Donisthorpea: Donisthorpe, 1915d: 212; in Formicina: Emery, 1916b: 240; in Acanthomyops: Ruzsky, 1925b: 44; in Lasius: Menozzi, 1921: 32; Müller, 1923: 125; Emery, 1925b: 230; Kuznetsov-Ugamsky, 1929a: 27. Subspecies of niger: Forel, 1874: 46; Mayr, 1886d: 429; Forel, 1892i: 307; Forel, 1904b: 386; Wheeler, W.M. 1906c: 322; Forel, 1913d: 438; Forel, 1915d: 53; Emery, 1916b: 240; Santschi, 1925g: 349; Karavaiev, 1927c: 280; Menozzi, 1936d: 305; Menozzi, 1939a: 312. Status as species: Saunders, E. 1880: 209; André, 1882b: 192; Nasonov, 1889: 22; Emery, 1897f: 238; Ruzsky, 1902d: 16; Emery, 1908d: 24; Bondroit, 1911: 11; Donisthorpe, 1915d: 212; Bondroit, 1918: 25; Stitz, 1939: 279; Novak & Sadil, 1941: 101; Röszler, 1942a: 53; Stärcke, 1944a: 153; Wilson, 1955a: 77; Baroni Urbani, 1971c: 200; Kutter, 1977c: 227; Collingwood, 1979: 97; Yamauchi, 1979: 156; Collingwood, 1982: 285; Kupyanskaya, 1990: 218; Atanassov & Dlussky, 1992: 237; Seifert, 1992b: 13. Senior synonym of americanus, pannonica and material of the unavailable names alienoamericanus, flavidus, turkmenus referred here: Wilson, 1955a: 77.
 * americanus. Lasius niger var. americanus Emery, 1893i: 639 (w.q.m.) U.S.A. Wheeler, G.C. & Wheeler, J. 1953c: 147 (l.). Subspecies of niger: Wheeler, W.M. 1904e: 305; Forel, 1900e: 285; Buren, 1944a: 296. Raised to species: Gregg, E.V. 1945: 530. Subspecies of alienus: Creighton, 1950a: 419. Junior synonym of alienus: Wilson, 1955a: 77.

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.

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.