Lasius fuliginosus

This species exhibits temporary social parasitism. Queens found new colonies by infiltrating an established nest of a different ant species, killing the queen and having the host workers care for her initial brood.

Identification
Shining black, legs brownish yellow; pubescence sparse, scattered erect hairs over dorsum. Head broadly cordate, emarginate posteriorly with rounded occipital lobes; genital margins incurving towards mandibular insertions. Maxillary palps short with segments 4, 5 and 6 subequal. Petiole thickened wedge shaped in profile, with feebly convex faces, dorsal margin narrow, convex or straight. Length: 4.0-6.0 mm (Collingwood 1979).

Key to Palaearctic Lasius workers

Distribution
Portugal to Japan and North India, South Italy to Finland (Collingwood 1979).

Distribution based on Regional Taxon Lists
Palaearctic Region: Albania, Andorra, Armenia, Austria, Azerbaijan, Belarus, Belgium, Bulgaria, Channel Islands, Croatia, Czech Republic, Denmark, Estonia, Finland, France, Georgia, Germany, Greece, Hungary, Iberian Peninsula, Isle of Man, Italy, Latvia, Liechtenstein, Luxembourg, Montenegro, Netherlands, Norway, Poland, Portugal, Republic of Korea, Republic of Moldova, Romania, Russian Federation, Slovakia, Slovenia, Spain, Sweden, Switzerland, The former Yugoslav Republic of Macedonia, Ukraine, United Kingdom of Great Britain and Northern Ireland.

Biology
This distinctive species is easily recognised by its shining black colour and broad head. Carton nests are constructed at the base of old trees, hedgerows and sometimes in sand dunes and in old walls. Colonies are populous, often polycalic with more than one focal nest and several queens. Workers forage above ground in narrow files throughout the day and night during warm weather, ascending trees and shrubs to tend aphids. The mandibles are relatively weak but small insects may be taken as food. Other competing ant species are repelled by aromatic anal secretions. Fertilised queens may be retained in the old nest or found fresh colonies through adoption by the members of the umbratus species group; mixed colonies with Lasius umbratus or Lasius mixtus have often been observed. Flight periods are irregular and have been recorded in all months from May to October. A number of local beetles occur with this species including members of the genus Zyras which exhibit protective mimicry. Waldén (1964), records an enormous nest measuring 63 x 55 x 55 cm found in a cellar near Göteborg and there are similar reports from outbuildings and cellars in England (Donisthorpe, 1927).

Wilson (1955) - Many European observers have reported independently on various aspects of the ecology of this ant, and together they present a reassuringly consistent picture. Lasius fuliginosus nests primarily in standing tree trunks and rotting stumps, and only occasionally in and around the roots of trees, under stones, and in open soil. In a random field survey in Germany, Gosswald (1932) recorded 63 nests in wood, 2 under stones, and 5 in open soil. He found the species nesting most commonly in old poplars and willows in dry meadows. It is often locally abundant; O'Rourke (1950) notes that in Ireland it may become the dominant ant in oak woods.

fuliginosus almost invariably constructs a carton nest. The composition of the carton has been analyzed by Stumper (1950), who finds that it consists primarily of macerated wood hardened with secretions from the mandibular glands. There may be some soil particles mixed in, especially in subterranean nests, but these constitute a very minor fraction. Stumper was unable to find supporting evidence for the old contention that several species of symbiotic fungi are normally grown in the carton walls.

fuliginosus forages during both the day and night, forming long, conspicuous columns which usually lead to trees infested with aphids or eoceids, the excreta of these latter insects forms a principal food source for the ant. In addition, many authors have observed workers carrying dead or crippled insects back to the nests.

Eidmann (1943) has studied overwintering in this species. A colony which he kept under observation through the autumn moved from a position in a tree bole to subterranean quarters directly beneath the tree. The winter carton nest had chambers twice the size of those in the summer nest, and its walls were conspicuously studded with grains of sand. Medium-sized and full grown larvae were found hibernating with the adults.

Winged reproductives have been taken in the nests from May to September. The nuptial flights apparently take place earlier than in other members of the genus; literature records span the period May 4 to July 27. The flights occur mostly in the afternoon, although some authors, such as Escherich and Ludwig (1906), have suggested that they occur at night also. According to Donisthorpe (1927), the mating behavior shows early signs of parasitic degeneration. There is a marked decrease in the size difference between the two sexes, and the nuptial flight appears to have been partly suppressed. In one case Donisthorpe observed nestmates copulating on vegetation in the immediate vicinity of the parent nest.

Donisthorpe (1922) has also reviewed the extensive literature on colony founding in this species. It has been proven without any doubt to be a temporary social parasite on Lasius umbratus (= Lasius mixtus), which species was defined in the old sense and may well include Lasius rabaudi also. Numerous mixed colonies have been found in nature, and successful adoptions of dealate queens by host colonies have been repeatedly obtained under artificial conditions. This habit places fuliginosus in the extraordinary position of being a social hyperparasite, since Lasius umbratus is parasitic itself on members of the subgenus Lasius. In more recent years, Stareke (1944) has obtained the experimental adoption of fuliginosus queens by colonies of rabaudi (= Lasius meridionalis), Lasius niger, and Lasius alienus.

Nomenclature

 *  fuliginosus. Formica fuliginosa Latreille, 1798: 36 (w.q.m.) FRANCE. Hauschteck, 1962: 219 (k.). Combination in Lasius: Mayr, 1861: 49; in Donisthorpea: Donisthorpe, 1915d: 188; in Formicina: Emery, 1916b: 242; in Acanthomyops: Forel, 1916: 460; in Lasius (Dendrolasius): Ruzsky, 1912: 630; Müller, 1923: 132; Emery, 1925b: 236; Wilson, 1955a: 138. See also: Yamauchi, 1979: 171; Collingwood, 1982: 292; Kupyanskaya, 1989: 783; Atanassov & Dlussky, 1992: 243.

Worker
Wilson (1955) - (1) Head usually deeply concave in full face, the depth of the concavity 0.06 mm. or more except in some series from northeastern Asia.

(2) Antennal scapes short-elliptical in cross-section, so that for most of their length the minimum width at any point is 0.8 X the maximum width at that point or greater.

(3) Petiole in frontal view broadest at about the level of the dorsal margin of the anterior foramen, gradually narrowing to the top. The dorsolateral angles broadly and evenly rounded; the dorsal margin narrow, convex to feebly emarginate. In side view the petiole symmetrical, with both faces feebly and evenly convex, tapering together to form a narrow-U-shaped dorsal crest.

(4) The hairs of the exposed gastric tergites shorter than in Lasius spathepus and Lasius crispus, rarely longer than 0.08 mm. and probably never surpassing the longest hairs of the pronotum. The appendages covered with dense appressed-to-decumbent pubescence but with few or no standing hairs.

Queen
Wilson (1955) - (1) HW 1.41 mm. (Odawara, Japan) to 1.65 mm. (England).

(2) Lacking the "beta" characteristics of the spathepus queen, i.e. the occipital margin in full face is only weakly concave, the head is about as long as broad or longer, and the mandibles are not exceptionally reduced relative to the remainder of the head.

(3) The entire body, exclusive of the appendages and (in European series) the anterior half of the head, covered with abundant, coarse suberect-erect hairs. In occasional specimens these hairs are rather sparse on the gastrict tergites, but this may be due to wear. The entire body is covered with appressed ground pubescence of varying density which partly obscures the smooth, shining cuticular surface.

(4) Petiolar lateral outline as in worker. Frontal outline typically as in worker and dorsal margin showing same degree of variation as in that caste; occasionally the broadest level is well above its usual location at the dorsal margin of the anterior foramen.

(5) Median clypeal carina feebly developed (see Lasius buccatus).

Male
Wilson (1955) - (1) HW 1.00 mm. (Kiev) to 1.24 mm. (Innsbruck).

(2) Scape short-elliptical to circular in cross-section.

(3) Petiolar outline in side view similar to that of the worker, differing only in being generally thicker. In frontal view the broadest point is at the level of the dorsal margin of the anterior foramen or higher; the dorsal margin is convex in all series examined.

(4) Pygostyle similar to that typifying the subgenus Lasius: thumb-shaped, nearly as broad near the tip as at the basal attachment.