A taxonomic account of the genus Labus de Saussure , 1867 ( Hymenoptera , Vespidae , Eumeninae ) with descriptions of three new species

Three new species, namely Labus edentatus sp. n. from China, L. sparsipunctus sp. n. from Thailand and L. robustus sp. n. from Indonesia are described and illustrated. Both L. amoenus van der Vecht, 1935 and L. pusillus van der Vecht, 1963 are newly recorded from China and Vietnam, and L. angularis van der Vecht, 1935 is also firstly recorded from China. An updated key to the world species of the genus Labus is provided.


Introduction
The genus Labus de Saussure is an Oriental genus containing 13 species (Girish Kumar et al. 2014) each of which is relatively slender with a petiolate metasoma and body length mainly 6.0-8.0 mm.De Saussure (1855Saussure ( , 1867)), van der Vecht (1935Vecht ( , 1963)), Giordani Soika (1960Soika ( , 1973Soika ( , 1986Soika ( , 1991)), Gusenleitner (1988), and Girish Kumar et al. (2014) made important contributions to the taxonomy of the genus.During this study of the genus Labus collections from Vietnam, Thailand, Malaysia, China, Philippines, Sri Lanka and Indonesia which are deposited in American Museum of Natural History in New York, three new species are confirmed by comparison with known species.In addition, both L. amoenus van der Vecht, 1935 andL. pusillus van der Vecht, 1963 are newly recorded from China and Vietnam, and L. angularis van der Vecht, 1935 is also firstly recorded from China.In the present paper, these three new species are described and illustrated in detail, and some main characters of other known species are provided with some related figures.In addition, an updated key to the world species of Labus is also given.

Materials and methods
The specimens examined are deposited in the American Museum of Natural History (USA), Chongqing Normal University (China), Queen Sirikit Botanic Garden (Thailand), and Yunnan Agricultural University (China), respectively.Descriptions and measurements were made under a stereomicroscope (Nikon SMZ1500), and all figures were taken with Microptics-USA/Visionary Digital photomicrographic system developed by Roy Larimer and multiple layers stacked using Helicon Focus.The ratios used throughout the descriptions were measured in the same magnification of the stereomicroscope.All measurements were taken as the maximal length of body parts measured.Body length was measured from the anterior margin of the head to the posterior margin of metasomal tergum 2. For the density description of punctures, "sparsely" means that interspaces are larger than punctures diameter, "moderately" means equal to the diameter, and "densely" means less than the diameter.Terminology principally follows van der Vecht (1935Vecht ( , 1963) ) and Girish Kumar et al. (2014).
The abbreviations used in the text are shown as follows:
Distribution.Oriental Region.2): body length 7.0 mm.Black, with the following parts yellow: a narrow and transverse band of clypeus basally (Fig. 2), a widely interrupted band on pronotum anteriorly (interruption less than each marking), a small spot on upper part of mesepisternum; outer margin of tegula anteriorly and posteriorly, parategula, two transverse spots on scutellum posteriorly, apical lamellae of propodeum, a small apical spot of fore femur inside, a large spot at outer side of fore and mid tibiae, a small spot on hind tibiae basally, narrow apical bands of T1-T2 and S2; apex of mandible, A12 beneath, and fore and mid tibiae dark ferruginous with exception of yellow spots.Wings slightly infuscated.

Labus edentatus
Head.In front view head (Fig. 2) slightly wider than high, its sides rounded; clypeus sparsely punctate, clypeal width 1.35× length, weakly convex at basal half, anterior portion less produced and with wide emargination in the middle, clypeal total width 4.6× its apical width, apical width 2× emargination depth, its teeth short and blunt; frons convex and densely punctate, inter-antennal carina continued on lower part of frons, frontal fovea deep, almost circular and distinctly defined (Fig. 3).
Mesosoma.Anterior angles of pronotum projecting only slightly, pronotal transverse carina obsolete; punctures on pronotum, mesoscutum, mesepisternum and scutellum slightly denser and their interspaces duller than those on frons; metanotum with an acute tubercle in the middle; propodeum posteriorly on each side without a tooth above the apical spine formed by the submarginal carina (Fig. 5); dorsal area of propodeum sparsely punctate and the interspaces between punctures coriaceous, posterior area with dense setae, lateral area obviously coriaceous.
Metasoma.Metasomal petiole (Fig. 4) long and moderately slender, total length of petiole 6.19× basal width and 2.6× apical one, swollen part of metasomal petiole slightly longer than (1.07×) half of the length of the petiole, linear part of petiole rugosely punctate, swollen part coriaceous and with scattered minute punctures; each of T2 and S2 with an apical translucent lamella, and microscopically sculptured, sparsely covered with extremely minute and shallow punctures.
Remarks.This species resembles L. pusillus van der Vecht, 1963 by propodeum posteriorly on each side without a tooth above the apical spine formed by the submarginal carina and swollen part of metasomal petiole as long as or longer than half of the length of the petiole.It differs from L. pusillus and all other members of the genus by the following character combination: the median portion of clypeus less produced, its emargination wide medially and lateral teeth slightly blunter (Fig. 2), frontal fovea (Fig. 3) much larger than the anterior ocellus and bigger than that in L. pusillus (Fig. 37).

Labus sparsipunctus
Head.Head (Fig. 8) in front view wide almost as long as high, its sides rounded; clypeus sparsely setose and punctate, interspaces between punctures obviously shiny, clypeal width 1.25× length, weakly convex at basal half, anterior and median portion narrowly produced (clypeal total width 7.0× its apical width) and with U-formed emargination, lateral teeth acute, emargination width 1.25× its depth; frons convex and sparsely punctate and interspaces between punctures obviously shiny, interantennal carina continued on lower part of frons, frontal fovea deep, elliptical and defined (Fig. 9).
Mesosoma.Anterior angles of pronotum projecting slightly, pronotal anterior and transverse carina obsolete, punctures on pronotum dense, interspaces less than punctures, mesoscutum and scutellum sparsely punctate, interspaces more than punctures, mesepisternum dull and coriaceous, with sparse punctures; metanotum with a small and blunt tubercle in the middle; propodeum posteriorly on each side without a tooth above the apical spine formed by the submarginal carina (Fig. 11); dorsal area of propodeum sparsely punctate and the interspaces between punctures shiny, posterior area with dense setae, lateral area dull and obviously coriaceous.
Metasoma.Metasomal petiole relatively long and slender, total length of petiole 7.53× its basal width and 2.76× apical one, swollen part of metasomal petiole almost as long as half of the length of the petiole and shiny with scattered minute punctures; linear part of petiole slightly rugosely punctate; each of T2 and S2 with an apical translucent lamella, and sparsely covered with extremely minute and shallow punctures.
Male (Figs 7,10,12).Body length 7.0 mm.Sculpture, punctuation, setae, and coloration as in female except as follows: clypeus except anterior margin (Fig. 10), scape ventrally and mandible except apex yellow; two apical flagellomeres yellowish brown; spots on legs larger than those in female; clypeal width 1.23× its length, total width 7.4× apical width, apical width 2.5× emargination depth, emargination narrower and shallower than that in female; A13 backward reaching basal margin of A11; punctures on frons, pronotum and mesoscutum relatively denser than those in female; linear part of petiole (Fig. 12) narrower and longer than female, total length of petiole 8.07× its basal width and 2.10×apical one, swollen part less than (0.8×) half of the length of the petiole; other characters same as those in female. Distribution.Thailand.
Remarks.This species is allied to L. clypeatus van der Vecht, 1935 from Indonesia, with which it has the following characters in common: propodeum posteriorly on each side without a tooth above the apical spine formed by the submarginal carina, and swollen part of metasomal petiole less than half of the length of the petiole (Fig. 12).It differs from L. clypeatus and all other members of the genus by the following character combination: frons sparsely punctate and more shiny between these punctures in female (Fig. 8), anterior and median portion of clypeus narrowly produced (Figs. 8,10), and total length of metasomal petiole at most 8.07× its basal width, whereas in L. clypeatus the petiole length more than 9× basal width (van der Vecht 1935).
Etymology.The specific name sparsipunctus is derived from two Latin words: sparsus and punctus, referring to frons sparsely punctate in female.Description.Male (Figs 13-14): body length 7.0 mm.Body black, with the following parts yellow: clypeus except anterior margin (Fig. 14), basal part of mandible, two anterior angles of pronotum; a small spot on upper part of mesepisternum; outer margins of tegula, parategula; two transverse nearly elliptical spots on scutellum posteriorly; apical lamellae of propodeum, small apical spots of fore and mid femora inside, outer sides of fore and mid tibiae, basal half at outer side of hind tibiae, narrow apical bands of T1-T2 and S2; apex of mandible, and fore and mid tibiae with exception of yellow spots dark ferruginous; A13 yellowish brown.Wings slightly infuscated.

Labus robustus
Head.Head in front view (Fig. 14) wide slightly longer than (1.09×) high, its sides somewhat flattened; clypeus sparsely setose and shiny, punctures indistinct, clypeal width as long as length, weakly convex at basal half, anterior and median portion produced and with U-formed emargination, the emargination width 1.75× its depth and teeth acute, clypeal total width 4.86× its apical width; frons convex, coarsely and densely punctate, and with a longitudinal furrow in the middle, inter-antennal carina not continued on lower part of frons.
Mesosoma.Anterior angles of pronotum projecting moderately, pronotal anterior and transverse carina present, punctures on pronotum, mesoscutum and scutellum similar to those on frons; mesepisternum coarsely punctate and punctures slightly denser than that of other parts; metanotum with a small tubercle in the middle; propodeum posteriorly on each side with a moderate tooth above the apical spine formed by the submarginal carina (Fig. 15); dorsal area of propodeum sparsely punctate and the interspaces between punctures coriaceous, posterior area with dense setae, lateral area dull, coarse, and slightly rugose.
Metasoma.Metasomal petiole (Fig. 16) short and stout, total length of petiole 4.32× basal width and 2.16× apical width, swollen part of metasomal petiole as long as half of the length of the petiole and shiny with scattered minute punctures; linear part of petiole distinctly rugosely punctate and relatively wider and stouter than other species of the genus excluding L. postpetiolatus Gusenleitner; T2 and S2 with apical translucent lamellae, and sparsely covered with extremely minute and shallow punctures.
Remarks.This species resembles L. postpetiolatus Gusenleitner, 1988 from Thailand by metasomal petiole short and stout, its total length about 4.5× basal width, and its linear part distinctly rugosely punctate (Figs 16,19).It differs from L. postpetiolatus and all other members of the genus by the following character combination: the tooth above the apical spine of propodeum comparatively blunter, lower, and closer to the apical spine (Fig. 15); swollen part of metasomal petiole sparsely punctate (Fig. 16), in L. postpetiolatus punctures more densely punctate (Fig. 19).
Etymology.The specific name is derived from one Latin word: robustus, referring to metasomal petiole stout.
Diagnosis.Clypeus somewhat shorter, the median portion less produced, its teeth slightly blunter; spine of metanotum somewhat blunter; posterior excavation of propodeum not margined above, and propodeum posteriorly on each side without a tooth above the apical spine formed by the submarginal carina; apical lamellae sharp; metasomal petiole slender, its total length more than 9× basal width, the swollen part more than 3× as wide as the basal linear part, about 2/3× as long as the lineal part and more gradually swollen than in L. spiniger de Saussure, 1867; punctuation the same as in L. spiniger (van der Vecht 1935).
Distribution.Vietnam; Indonesia (Java).Diagnosis.The original description of the species gave insufficient detail to distinguish it from other species.Head wider than long, without indentation; metasomal petiole punctate and without bulging, widening a little back and forth, then truncated right to its articulation, and carrying two insensitive tubercles in front of its middle; S2 bell-shaped, but very short, appreciably wider than long, strongly swollen above and below, and offering at its posterior edge a strong duplication of the teguments; second cubital cell strongly narrowed towards the radial and prolonged at its posterior border, but at its external angle; antennal hooks very small; scape yellow beneath; pronotum anteriorly with a yellow, narrow, perfectly regular and medianly interrupted band, and each of T1-T2 and S2 with a yellow apical band; legs ferrugineous, with some parts of femora and mid tibia black (de Saussure 1855; van der Vecht 1935).
Material examined.No specimens examined.
Diagnosis.Body black, with yellowish white and brown markings.Yellowish white markings are as follows: anterior margin of horizontal portion of pronotum, parategula, at apical lamellar spine of the propodeum, fore tibiae on outer side, mid tibiae with a small yellow mark at base, a narrow thin transverse band at the posterior apex of T1, and a thin transverse band on T2 and S2. Brown markings are as follows: tegula (almost brownish black) except a small yellow mark at apex, propodeal valvula, and tarsi (partly); wings rather strongly infuscated; head and thorax densely and coarsely punctate; frontal fovea large, distinctly larger than the anterior ocellus, concavity of fovea divided by a blunt and low median ridge; pronotal spine rather short and conical; propodeum on each side with a long and sharp tooth above the apical lamellar spine; petiole coarsely and densely punctate, except on the swollen part which is sparsely and more finely punctate; swollen part as long as half of the length of the petiole (van der Vecht 1963; Girish Kumar et al., 2014).
Diagnosis.Body (Figs 25-26) length 6.5-8.0 mm; head (Figs 27,31) in frontal view slightly longer than wide, its sides flattened; in female, frontal fovea much deeper, distinctly defined, and rounded (Fig. 28); propodeum posteriorly on each side with a moderate tooth above the apical spine formed by the submarginal carina (Fig. 29); metasomal petiole long and slender (Fig. 30), total length of petiole 7.2× basal width and 2.57× apical width, swollen part slightly less than (0.98×) half the length of the petiole and with uniform punctures.
Diagnosis.Body (Fig. 17) length 7.0 mm; propodeum (Fig. 18) posteriorly on each side with a sharply acute and high tooth above the apical spine formed by the submarginal carina, the tooth far away from apical spine; linear part of metasomal petiole (Fig. 19) short and stout, and distinctly rugosely punctate, total length of petiole 4.51× basal width and 2.03× apical width, swollen part of metasomal petiole longer than half of the length of the petiole and densely punctate. Distribution.Thailand.
Diagnosis.Closely allied to L. amoenus van der Vecht, 1935 with the following characters in common: head higher than wide, the sides slightly flattened; anterior lateral angles of pronotum each produced into a sharp spine; metanotum with sharp median tooth; propodeum, as seen in profile, with short blunt tooth above the apical tooth; metasomal petiole relatively long and slender (Van der Vecht 1935, fig. ia); the morphological characters separating the two species are as follows: frontal fovea deeper and slightly smaller, circular or even a little wider than long, distinctly defined; frons not carinate; median part of scutellum regularly rounded posteriorly, without prominent angles; punctures on head and thorax very slightly coarser than L. amoenus; body black, without yellow spots, and with the following parts red: an ill-defined transverse spot at base of clypeus, a rather wide transverse band at anterior margin of horizontal surface of pronotum, a small spot in upper part of mesepisternum below tegulae, a transverse band on scutellum, interrupted by the black median groove, and the greater part of the metasomal petiole (van der Vecht 1963). Distribution.Indonesia.
Diagnosis.Allied to L. angularis van der Vecht, 1935 mainly distinguished by the shape of clypeus which is very weakly marginalized at the apex, with apical teeth replaced by two undeveloped tubercles; punctures on frons thicker than those in L. angularis and on thorax visibly larger, punctuation of metasoma approximately as in L. angularis (Giordani Soika 1991). Distribution.Indonesia.
Diagnosis.Very closely allied to L. spiniger de Saussure, 1867(van der Vecht 1935: 165), but the horizontal part of the propodeum more distinctly punctate, the punctures not much closer, but slightly larger, and better defined; the sides of the propodeum more shiny between the punctures (rugose and rather dull in L. spiniger), the transverse ridge at apex of propodeum more pronounced, as seen in profile forming a more distinctly projecting tooth; swollen part of metasomal petiole relatively longer, nearly half as long as the petiole; second metasomal segment relatively longer (length: width = 1.2 : 1, in L. spiniger = 1.1: 1); metasomal petiole red, with narrow yellow apical band; legs ferrugi-nous, coxae and trochanters dark brown to black, fore femur I with vague yellow spot at apex, mid and hind femora fuscous at base, hind tibiae fuscous at apex, tarsal segments 2-5 of mid legs and 1-5 of hind legs fuscous (van der Vecht 1963). Distribution.Indonesia.

Key to the world species of Labus de Saussure
In the below key, information on L. clypeatus van der Vecht, L. exiguus (de Saussure), L. humbertianus de Saussure, L. rufomaculatus van der Vecht, L. sumatrensis Giordani Soika and L. vandervechti Giordani Soika is extracted from the original descriptions, and the characters of other species were studied on specimens.The linear part of metasomal petiole short and wide, and distinctly rugosely punctuate, total length of petiole about or less than 4.51× basal width (Figs 16,19) ... 6 - The linear part of metasomal petiole long and narrow, and just slightly rugosely punctuate, total length of petiole at least more than 6.5× basal width (Figs 23,30,(32)(33)44)