Lasius spathepus

This species exhibits temporary social parasitism. Queens found new colonies by infiltrating an established nest of another Lasius species, killing the queen and using host workers to care for her initial brood.

Identification
Radchenko (2005) - Lasius spathepus is the most peculiar species of the genus, especially for the characters of its queens. Workers are similar to those of Lasius orientalis by their distinctly flattened scape, but well differ from the latter by the much thinner, narrowing at the top petiolar scale. On the other hand, the shape of petiolar scale recalls Lasius nipponensis, but in the latter the scape is not flattened.

Distribution
Radchenko (2005) - Southern part of Russian Far East (known only from one locality: Primorsky Region, Anisimovka), Korean Peninsula, Japan (all four main Islands).

Distribution based on Regional Taxon Lists
Palaearctic Region: Democratic Peoples Republic of Korea, Japan, Republic of Korea, Russian Federation.

Biology
This species is likely to be a temporary parasite, but its host is.

Nomenclature

 *  spathepus. Lasius spathepus Wheeler, W.M. 1910b: 130, fig. 1 (q.) JAPAN. Wheeler, W.M. 1928d: 122 (w.); Wilson, 1955a: 149 (m.). Combination in L. (Dendrolasius): Emery, 1925b: 236. Subspecies of fuliginosus: Teranishi, 1927: 90. Revived status as species: Wheeler, W.M. 1928d: 122. See also: Teranishi, 1940: 76; Wilson, 1955a: 149; Yamauchi, 1979: 172; Kupyanskaya, 1989: 787; Kupyanskaya, 1990: 231; Radchenko, 2005a: 89.

Worker
Wilson (1955) - (1) Head broader, occiput usually less concave, and scapes shorter relative to head width than in other Dendrolasius.

(2) Antennal scapes flattened to the extent that for most of their length the minimum measurable width at any point is less than half the maximum measurable width at the same point. Tibiae and metatarsi also noticeably flattened.

(3) Hairs of scapes and legs sparser and longer than in other Dendrolasius. The standing hairs seen in relief when the hind tibia is viewed in the plane of its minimum width are often half as long as the greatest width measurement obtained along the length of the tibia in this view, or longer. Tibial hairs appressed to suberect, the majority tending to decumbent.

(4) The petiole seen in frontal view subrectangular; the dorsal border always emarginate to some degree. In side view the anterior face curving back abruptly just above the level of the spiracle, in contrast to the posterior face, which is gently and evenly convex from the posterior foramen to the crest.

(5) Propodeum viewed from the side typically higher and more prominent relative to the thorax than in other Dendrolasius. A single series from Nanzan, Korea, represents an extreme deviant from this character and is well within the range of variation of fuliginasus.

Radchenko (2005) - Petiolar scale (seen in profile) thin, distinctly narrowing to the top, asymmetrical; when seen in front or from behind it gradually narrowing to the top, with straight or slightly notched dorsal crest; scape distinctly flattened, ratio of min/max diameters of the scape ≤ 0.5; head with convex sides, gradually and slightly narrowing anteriorly, with emarginate occipital margin; scape and legs with numerous short subdecumbent hairs; promesonotal dorsum and occipital margin of the head with relatively sparse and long standing hairs.

Queen
Wilson (1955) - (1) Averaging and ranging larger than other Dendrolasius; HW 1.96-2.03 mm.

(2) Head much broader than long, with a deeply emarginated occipital border and strongly convex sides which curve in sharply at the mandibular insertions. The mandibles exceptionally small relative to the head.

(3) Scapes, femora, tibiae, and metatarsi greatly flattened, the minimum width of the scape at midpoint about half the maximum width.

(4) The broad surfaces of the scape coarsely and evenly punctate.

(5) The dorsal border of the petiole emarginate for nearly its entire extent. In side view the scale is anteriorly truncated as in the worker.

(6) The scapes, tibiae, and metatarsi densely covered with long, predominantly suberect, coarse, silvery yellow hairs. On the tibiae and metatarsi these form two layers, those in the lower, short and densely packed and those in the upper, long, curved and sparse.

(7) Ground pubescence completely lacking on the body. Hairs are limited mostly to the mandibles, clypeus, gula, posterior third of the head, petiole, anterior first gastric tergital surface and posterior gastric tergital margins. The alitrunk is completely lacking in pilosity of any kind except for a few scattered short hairs on the propodeum.

(8) The body is very feebly sculptured and strongly shining, except for the petiole and anterior clypeal margin, which are shagreened; and the mandibles, which are longitudinally striate.

(9) Median clypeal carina well developed posteriorly but vanishing in the planed, shagreened anterior fourth of the clypeus.

Radchenko (2005) - Holotype: HL1 = 1.66, HL2 = 1.85, HW 1 = 2.03, HW 2 = 1.28, SL = 1.55, OL = 0.43, AL = 2.53 mm; CI = 1.22, CLI = 1.11, CWI = 1.59, SI1= 0.93, SI2 = 0.76, OI = 0.21.

Petiolar scale (seen in profile) thin, distinctly narrowing to the top, asymmetrical; head with deeply emarginate occipital margin, cordiform, distinctly wider than long; scape and legs, including the first tarsal joint, remarkably flattened, ratio of min/max diameters of scape and hind tibiae ≤ 0.4; legs with dense decumbent to subdecumbent pubescence; antennal scape with abundant subdecumbent to suberect hairs; head, alitrunk and gaster with very short and sparse decumbent pubescence, alitrunk dorsum without standing hairs.

Male
Wilson (1955) - (1) Averaging and ranging larger than other Dendralasius; HW 1.13-1.27 mm.

(2) Scapes and tibiae distinctly flattened.

(3) Petiole in frontal view distinctly emarginate and much broader than in other Dendrolasius. Petiolar outline in side view similar to that described for the worker.

(4) Pygostyle as in Chthonolasius, i.e, thicker than in Lasius s. s. and tapering gradually from base to tip. The subgenital plate distinctive in shape: the posterior margins between the setiferous lobes and posterior angles more deeply convex than in Lasius fuliginosus and Lasius crispus, causing the setiferous lobes to project back more prominently.

(5) Scape and tibial pilosity longer and sparser than in other Dendrolasius.

Type Material
HOLOTYPE. A queen in the labelled "Japan. Kuwana Coll. 1910."

Radchenko (2005) - Holotype queen: “Japan, Kuwana coll., 1910”, “Type”, “Holotype Lasius spathepus Wheeler”, "M.C.Z. type 71691”.