Lasius niger

This is one of the commonest European species and is often especially evident at sites of human disturbance including towns, villages and quarries. Nests may occur in walls, pavements, tree stumps in open woodland, pasture and open heath. Occasionally earth mounts are formed and foraging tracks are frequently covered by surface tunnels of earth. This species is aggressive and readily attacks other ants. Nests are single queened and moderately populous with several hundred up to 10,000 workers. Aphids on shrubs and herbs as well as subterranean species are tended. Mating swarms occur from July to late August and in some years huge numbers may fly over a large district on the same date. (Collingwood 1979)

Identification
The worker is best distinguished by its abundant standing appendage pilosity combined with the clypeal outline and mandibular dentition characteristic of the "niger complex" (Lasius niger, Lasius alienus, Lasius emarginatus, Lasius productus). Over most of Europe and in western North America niger has a scape index regression zone intermediate between those of Lasius brunneus and emarginatus, but in peripheral Eurasian populations this zone shifts to overlap that of emarginatus. The male is best distinguished by the possession of abundant standing pilosity on the appendages combined with the "niger type" mandible described below. (Wilson 1955)

Greyish brown to dark brownish black, mid body occasionally somewhat paler. All appendage surfaces including scapes and tibiae with abundant erect hairs. Length: 3.5-5.0 mm (Collingwood 1979).

Distribution
This species has the northernmost range of the four members of the niger complex. In Eurasia it is found from Scotland and southern Fennoscandia south to Morocco, Algeria, and the offshore Atlantic Islands, east through Lebanon, Afghanistan, and the Himalayan plateau to central China and Formosa, then north to northern Russia, southern Yakutsk, and Kamchatka. In North America it ranges from the Pacific Northwest through most of the Great Basin, the Rocky Mountains, and northern Sierra Nevada. (Wilson 1955)

Holarctic from Western United States to Japan, North Africa to Finland (Collingwood 1979).

This taxon was described from Europe.

Biology
Wilson (1955) - Gosswald (1932) has presented a detailed and informative account of the habitat preferences and nesting habits of this species in Germany. He found it to be one of the most abundant and adaptable native ants. It occurs in deciduous, coniferous, and mixed forests, along forest borders, in hedgerows, and in open meadows; it thrives on cultivated land and occasionally enters houses. In forests it tends to nest in rotting tree trunks. In exposed situations with little vegetation cover, it nests mostly under stones. In meadows, along grass-grown paths and forest gardens, and in gardens, it frequently builds earthern mounds, especially where the soil is moist and the ground vegetation dense. Such mounds are irregular in shape and apparently designed to surmount the surrounding vegetation, with the result that they are often quite massive and may exceed 50 cm. in height. In a random field sample, Gosswald found 625 nests under stones, 350 in mounds, and 130 in rotting wood. The species is said to occasionally construct carton nests out of macerated plant material and humus, especially when it nests under stones in pine woods; the carton material closely resembles that characteristically manufactured by Lasius fuliginosus.

The North American population shows a similar latitude in habitat preferences. Field notes supplied me with 16 collections by A. C. Cole and Borys Malkin seem to indicate a general preference for drier and more open situations. The majority of the 16 were taken in open forest of variable composition, while several were taken in meadows and grassy roadstrips. One was taken in a dry rabbitbrush association (Chrysothamnus) near Eagle Nest, N. Mex. Another was taken near timberline in a zone of stunted fir (Bloomington Peak, Wasatch Mts., Idaho; Malkin). The Eagle Nest colony was found in soil at the base of a bush; all of the others were taken under stones.

The previously published Asiatic records seem to indicate broad adaptability also. The Yalung-Yangtse collections recorded by Eidmann (1941) were made both in moist river valleys and in the high grassland of the Tibetan Plateau. All were from under stones. Kuznetzov-Ugamskij (1929a) notes that in the Ussuri region this species occurs under the "widest environmental conditions."

Ecological data accompanying several peripheral collections determined during this revision are noteworthy. On the Canary Islands (Gran Canaria, Teneriffe, La Palma) Wheeler (1927) found niger mostly in moist, shady spots between 1500 and 5000 feet. At Las Mercedes, Teneriffe (2500 feet), it was the only ant species found in a forest of tree-heath (Erica arborea) and laurel (Cerasus lusitanicus). At Ponta Delgada in the Azores niger occurred abundantly with Tetramorium caespitum, nesting under stones and foraging over the ground in files. In Lebanon, Christiansen (in litt.) took workers under rocks in mesophytic forest at Hammana and dealate queens from rotting wood in spruce forest above the Kammuoha Plain. Workers were also taken with the aid of a Berlese funnel from around the roots of grass growing on the banks of the Orontes River two miles south of Hermel. This last locality is surrounded by scrub desert and is ten miles from the nearest well developed woodland, representing an extreme habitat record for Lasius in general and a very extraordinary one for niger in particular.

Lasius niger has generalized food habits. Many authors have observed it gathering insect remains, floral nectar, and the honeydew (excreta) of Homoptera and larval Lycaenidae. Eidmann (1926) and others have suggested that the insect honeydew makes up the bulk of the diet. According to Donisthorpe (1927), in a review of the food habits of this species, niger has been observed occasionally to gather seeds of such plants as Viola, Galium, and Ranunculus; Scott (1926) has seen it collecting seeds of Chelidonium. But apparently no one has checked to see if the seeds are actually used as food.

The pastoral habits of niger have been the subject of an excellent study by Eidmann (ibid.). Certain aphids overwinter in the nests of niger and are brought out and placed on the host plants in the spring. At first the aphids are returned to the shelter of the nests each evening. Later, as the nights grow warmer, the herds are left permanently in place. Certain of the workers function as guards during the day, remaining constantly at fixed posts; one worker was observed to return to the same spot each day for eight days. The workers appear to reduce predation by the braconid Trioxys, and on several occasions Eidmann saw them in the act of driving off workers of other ant species. Biisgen (1891) has observed niger workers combating chrysopid larvae in similar fashion. By counting the number of workers returning to the nest gorged with honeydew, Eidmann estimated that a large colony of niger may consume as much as a liter of this material in the course of a summer.

According to Eidmann, niger is principally nocturnal. Its above-ground activity, as measured by the number of ants soliciting honeydew, is highest at midnight and lowest in the early morning. The workers do all they can to avoid light; in order to work above ground they build turret-shaped shelters around the bases of aphid-infested plants and connect these with the nest by means of covered pathways.

Eidmann (1943) has included this species in a general study of overwintering in ants. Most of the workers of the colony move deep into the center of the nest, concentrating in a few chambers. A small number remain with the aphids in the special chambers where these insects are housed. Brood, in the form of small larvae, may be present or lacking.

According to Donisthorpe (1926), who has undertaken a thorough review of the European literature on the subject, the nuptial flights of niger take place in the afternoon and early evening from early July to mid-September. There are no records of nuptial flights in North America, but winged reproductive have been taken in nido from July 3 (Sacramento Mts., N. Mex.) to September 1 (Alta, Utah). Stray males and queens, possibly engaged in a nuptial flight, were found at Heber, Utah, on September 7 (A. W. Grundmann). Eidmann (1926) has studied reproduction and nest-founding in this species in Germany. The pair copulate in flight, fall to the ground, and separate. The queen, without attempting to take flight again, soon drops her wings and seeks cover. The first eggs are laid the following spring, and the first adult brood hatches that summer. One queen was observed to go without food for 382 days in the normal course of founding a colony.

Nomenclature

 *  niger. Formica nigra Linnaeus, 1758: 580 (w.) EUROPE. Latreille, 1798: 43 (q.m.); Wheeler, G.C. & Wheeler, J. 1953c: 148 (l.); Hauschteck, 1962: 219 (k.); Imai & Kubota, 1972: 196 (k.). Combination in Lasius: Fabricius, 1804: 415; in Donisthorpea: Donisthorpe, 1915d: 200; in Formicina (Donisthorpea): Emery, 1916b: 240; in Acanthomyops: Forel, 1916: 460; in Lasius: Menozzi, 1921: 32; Müller, 1923: 124; Kuznetsov-Ugamsky, 1929a: 26; Wilson, 1955a: 59. Senior synonym of pallescens: Mayr, 1861: 49; of nigerrima: Emery, 1892b: 162; of alienoniger, emeryi, nitidus, minimus, transylvanica and material of the unavailable name pilicornis referred here: Wilson, 1955a: 59; of alienoniger: Kutter, 1977c: 14. Current subspecies: nominal plus pinetorum. See also: Imai, 1966: 119; Tarbinsky, 1976: 134; Kutter, 1977c: 227; Yamauchi, 1979: 152; Collingwood, 1982: 287; Kupyanskaya, 1990: 219; Seifert, 1992b: 27.
 * nigerrima. Formica nigerrima Christ, 1791: 513 (w.) no locality given. Junior synonym of niger: Emery, 1892b: 162.
 * pallescens. Formica pallescens Schenck, 1852: 55 (q.m.) GERMANY. Junior synonym of niger: Mayr, 1861: 49.
 * alienoniger. Lasius niger var. alienoniger Forel, 1874: 47 (w.q.) SWITZERLAND. Subspecies of niger: Finzi, 1924a: 14; Stärcke, 1944a: 154. Raised to species: Röszler, 1943: 44. Junior synonym of niger: Wilson, 1955a: 59; Kutter, 1977c: 14. Unrecognisable taxon, incertae sedis in Lasius: Seifert, 1992b: 48.
 * emeryi. Lasius niger subsp. emeryi Ruzsky, 1905b: 313 (w.) RUSSIA. Junior synonym of niger: Wilson, 1955a: 59. Unrecognisable taxon, incertae sedis in Lasius: Seifert, 1992b: 48.
 * nitidus. Acanthomyops niger subsp. nitidus Kuznetsov-Ugamsky, 1927e: 188 (w.) KAZAKHSTAN. Junior synonym of niger: Wilson, 1955a: 59. Unrecognisable taxon, incertae sedis in Lasius: Seifert, 1992b: 48.
 * minimus. Acanthomyops niger var. minimus Kuznetsov-Ugamsky, 1928b: 20 (w.) RUSSIA. Combination in Lasius: Kuznetsov-Ugamsky, 1929a: 26. Junior synonym of niger: Wilson, 1955a: 59. Unrecognisable taxon, incertae sedis in Lasius: Seifert, 1992b: 48.
 * transylvanica. Lasius transylvanica Röszler, 1943: 44 (w.q.m.) ROMANIA. Junior synonym of niger: Wilson, 1955a: 60. Unrecognisable taxon, incertae sedis in Lasius: Seifert, 1992b: 48.

Worker
Wilson (1955) - (1) More than 95 per cent of the workers within HW range 0.61-1.21 mm., exclusive of material from North Africa, the Balearics, Azores, Madeira, and eastern Asia, possess a SI between 95 and 103. This is a strongly allometric character (Fig. 5), with minimas (HW less than 0.61 mm.) ranging up to 109.

(2) As a corollary to (1), ML within this sample exceeds EW.

(3) Mandibular dentition characteristics of the niger complex: basal teeth two to four in number, equal in size, and spaced at even intervals; opposed to the neoniger complex, in which the two or three basal teeth are irregularly spaced and the central one of a set of three is often reduced in size.

(4) Clypeus characteristic of the niger complex: when the mandibles are opened and the head is viewed in perfect full face, the anterior border of the median clypeal lobe describes an even, broad parabolic curve, with the sides at least feebly convex and only occasionally meeting in a point at the midline; opposed to the more angular clypeal border of the neoniger complex. (See Pl. I, Figs. 2 and 3.) The clypeus is usually, but not always, keeled.

(5) Scapes and tibiae always with abundant standing pilosity, except in minimas with PW less than 0.47 mm. The inclination and density of this pilosity show striking geographic variation (see below). In general, niger complex workers with seta counts greater than 25 are almost certainly niger, but those with less might be alienus and should be determined with the aid of the allometry regression zones plotted in Figure 6.

In a sample of 165, with no more than 2 per nest series, PW range, 0.40-0.83 mm., mean with standard error 0.630 ± 0.005 mm., standard deviation 0.069 mm.

Thirty-four individuals each representing a different nest series were examined especially for dentition; 27 had three basal teeth, 5 had four, and 2 had four with the antepenultimate tooth reduced. in size; one lacked the second intercalary tooth.

Petiole outline more variable than in other members of the subgenus. Among 52 nest series examined especially for this character, the dorsal border was gently convex in 14, straight in 11, roundly concave in 22, and angularly concave in 5.

In a strong, reflected, artificial light, the body surface is subopaque to moderately shining. The degree of shininess varies inversely with the density of the pubescence and coarseness of the shagreened sculpturing, both independent and highly variable characters by themselves.

Body nearly or completely concolorous medium to blackish brown. Legs typically medium brown, scapes tending to yellowish brown.

Queen
Wilson (1955) - (1) Within the geographic limits stated in the first worker character above, queens with HW between 1.54 and 1.82 mm. have an SI between 72 and 80.

(2) As a corollary to (I), queens within this sample have a ML between 0.17 and 0.23 mm., with over 90 per cent falling within 0.18-0.21 mm.

(3) Clypeus and mandibular dentition as in worker.

(4) Scapes and fore tibiae with abundant standing hairs; seta count usually over 20 and often over 40. Inclination and density subject to geographic variation as in worker.

(5) Wings hyaline except for a small area distal to the axillary sclerites; this is a general niger complex character.

Male
Wilson (1955) - (1) Within the geographic limits stated in the first worker character above, SI 62-69, ML 0.14-0.16 mm.

(2) Mandible characteristic of the niger complex: primitive preapical cleft of Lasius pallitarsis and Lasius brunneus modified into a shallow angular depression placed centrally on the masticatory border or lacking altogether, so that the masticatory border curves gently inward from the apex and then outward to meet the basal border. The basal angle broadly rounded, the masticatory border curving gradually into the basal border. Denticles lacking on the masticatory border.

(3) The subgenital plate subrectangular, the posterior sclerotized, setiferous lobes not more than one-fourth as wide across their base as the plate itself but protruding past the unsclerotized posterior rim and reaching as far back as the level of the tips of the posterolateral flanges. A single series from Shriek, Belgium (A. Raignier leg.; MCZ), contains individuals with two distinct lobes, a single lobe, and several stages intermediate in the coalescence of two lobes.

(4) Long standing hairs present over most of the surfaces of the scape and fore tibia, but much sparser than in the worker and queen; seta count usually less than 5.

Additional References

 * Morrison, W.R. & Witte, V. 2011. Strong differences in chemical recognition cues between two closely related species of ants from the genus Lasius (Hymenoptera: Formicidae). Journal of Evolutionary Biology, 24: 2389–2397 (doi: 10.1111/j.1420-9101.2011.02364.x).