Lasius flavus

Identification
Clear yellow to brownish yellow. Body hairs on dorsum of gaster and alitrunk long; appendages and body covered with more or less thick adpressed pubescence, more dilute on head. No erect hairs on tibiae, scapes or genae. Scale thin in side view, low and broad in front view with dorsal margin mildly convex straight or in larger specimens occasionally emarginate. Size very variable in North European populations. Length: 2.2-4.8 mm (Collingwood 1979).

Distribution
North America to Japan; North Africa to Arctic (Collingwood 1979).

This taxon was described from Europe.

Europe
Collingwood (1979) - This species is very widely distributed and one of the most abundant in North Europe where it is a characteristic earth mound builder in pastures and along the periphery of woodlands but also nesting under stones in rocky areas. Colonies are started by one or more queens with primary pleometrose quite frequent. In North Europe nests in exposed places and in northern extremity of its distribution, L.flavus exhibits a wide range of worker size. On warm sites in southern areas usually in sandy lowland heath, worker size is small and much less variable. Eye ommatidium number is correlated with size and series of small workers with eyes with low ommatidium number are sometimes referred to Lasius myops Forel. However, queen size is constant regardless of worker size. L. myops is therefore regarded as a synonym of L.flavus. Individual nests may contain several thousand individuals and favourable nest sites, e. g. pasture sloping with a southern aspect, may be crowded with mound nests. This species, as with Lasius niger, tends to swarm on the same day in any one area and in years of abundant production of sexuals huge mating swarms may occur during late July or August. This species is hypogoeic, seldom occurring above ground, feeding on small insects and the exudate of subterranean root feeding aphids.

Nomenclature

 *  flavus. Formica flava Fabricius, 1782: 491 (w.) EUROPE. Latreille, 1798: 42 (q.m.); Wheeler, G.C. & Wheeler, J. 1953c: 152 (l.); Hauschteck, 1962: 219 (k.); Imai, 1966: 120 (k.). Combination in Lasius: Mayr, 1861: 50; Emery, 1925b: 231; Kuznetsov-Ugamsky, 1929b: 36; in Donisthorpea: Donisthorpe, 1915d: 216; in Formicina: Emery, 1916b: 241; in Acanthomyops: Forel, 1916: 460; Kuznetsov-Ugamsky, 1927e: 187; in Lasius (Chthonolasius): Ruzsky, 1914a: 59; in Chthonolasius: Ruzsky, 1925a: 288; Ruzsky, 1936: 90; in Lasius (Cautolasius): Wilson, 1955a: 112. Senior synonym of ruficornis: Roger, 1862c: 285; of ibericus and material of the unavailable name sancho referred here: Wilson, 1955a: 112; Seifert, 1990: 12; of apennina, brevicornis, fuscoides, helvus, microps (and its junior synonym claripennis), morbosa, odoratus, olivacea: Wilson, 1955a: 112. See also: Bernard, 1967: 359; Kutter, 1977c: 229; Collingwood, 1979: 96; Yamauchi, 1979: 160; Kupyanskaya, 1990: 222; Atanassov & Dlussky, 1992: 241.
 * brevicornis. Lasius brevicornis Emery, 1893i: 639, pl. 22, fig. 22 (w.q.m.) U.S.A. Junior synonym of flavus: Wilson, 1955a: 112.
 * fuscoides. Lasius flavus var. fuscoides Ruzsky, 1902e: 16 (w.) RUSSIA. Combination in L. (Chthonolasius): Ruzsky, 1914a: 61; in Chthonolasius: Ruzsky, 1925a: 288; in Acanthomyops: Kuznetsov-Ugamsky, 1927e: 187. Junior synonym of flavus: Wilson, 1955a: 112.
 * odoratus. Lasius flavus var. odoratus Ruzsky, 1905b: 282 (w.) RUSSIA. Junior synonym of flavus: Wilson, 1955a: 112.
 * claripennis. Lasius (Formicina) flavus subsp. claripennis Wheeler, W.M. 1917a: 527 (w.q.m.) CANADA. Junior synonym of microps: Creighton, 1950a: 422.
 * microps. Lasius (Formicina) brevicornis var. microps Wheeler, W.M. 1917a: 526 (w.) U.S.A. Wheeler, G.C. & Wheeler, J. 1953c: 152 (l.). Combination in L. (Chthonolasius): Creighton, 1950a: 422. Subspecies of brevicornis: Wheeler, G.C. & Wheeler, E.W. 1944: 253; of flavus: Creighton, 1950a: 422. Senior synonym of claripennis: Creighton, 1950a: 422. Junior synonym of flavus: Wilson, 1955a: 112.
 * morbosa. Formicina flava var. morbosa Bondroit, 1918: 28 (w.q.) FRANCE. Junior synonym of flavoides: Emery, 1925b: 231; of flavus: Wilson, 1955a: 112.
 * apennina. Lasius (Chthonolasius) umbratus var. apennina Menozzi, 1925d: 34 (w.) ITALY. Menozzi, 1932a: 8 (q.m.). Subspecies of flavus: Menozzi, 1932a: 8. Junior synonym of flavus: Wilson, 1955a: 112.
 * ibericus. Lasius (Chthonolasius) umbratus st. ibericus Santschi, 1925g: 349, fig. 2 (w.) SPAIN. Junior synonym of flavus: Wilson, 1955a: 112.
 * olivacea. Lasius (Lasius) flavus var. olivacea Karavaiev, 1926e: 194 (w.) CAUCASUS. Junior synonym of flavus: Wilson, 1955a: 113.
 * helvus. Lasius helvus Cook, 1953: 326, figs. (w.) U.S.A. [Also spelled helveolus, on p. 327.] Junior synonym of flavus: Wilson, 1955a: 113.