Three new species of the genus Gnamptogenys ( Hymenoptera , Formicidae ) from southern China with a key to the known Chinese species

Three new species of the genus Gnamptogenys Roger, 1863 are described from southern China: Gnamptogenys dentihumera Chen, Lattke & Zhou, sp. n., Gnamptogenys nanlingensis Chen, Lattke & Zhou, sp. n. and Gnamptogenys quadrutinodules Chen, Lattke & Zhou, sp. n. A distribution map and an identification key to workers for the known species of China are provided.


Introduction
Gnamptogenys Roger, 1863 is the most diverse ant genus in the subfamily Ectatomminae, which is distributed throughout the tropical region except for the African and Malagasy areas (Lattke 1995(Lattke , 2003)).Up to now, about 137 species have been described from all over the world (Bolton 2016).There existed some confusion about the definition of the genus until Brown revised the tribe Ectatommini and redefinition Gnamptogenys in 1958.Beyond that, Lattke did a lot of work in the genus (Lattke 1995(Lattke , 2003(Lattke , 2004(Lattke , 2007)).He revised the New World species and provided an identification key to the species and made a comprehensive biogeographic analysis of the genus Gnamptogenys, illustrating a cladistic biogeographic scenario and recognizing the several areas of endemism.He also revised all species of Gnamptogenys in Southeast Asia and Austrilia, and discussed their phylogenetic relationships based on nineteen terminal taxa and sixty morphological characters.
The first described species of the genus, G. bicolor (Emery 1889), was recorded in China by Wheeler (1930).In 1948, Brown described the G. panda, in Sichuan province, China.Further work was carried out on the Gnamptogenys fauna of China by later researchers (Wu and Wang 1995, Xu 1996, 2002, Zhou 2001, Lattke 2004, Terayama 2009), and the sporadic results were summarized in two checklists (Zhou and Ran 2010;Guénard and Dunn 2012).In terms of all taxonomic decisions mentioned, only seven Gnamptogenys species are recognized in China: G. bicolor (Emery, 1889); G. coccina Zhou, 2001;G. panda (Brown, 1948); G. sinensis Wu & Xiao, 1987; G. sichuanensis Lattke, 2004 and G. taivanensis (Wheeler, 1929).Comparing with the potential distribution area, this quantity is surprisingly small, an apparent indication that the diversity of Gnamptogenys in China is poorly known undiscovered, and there are still more species to be found certainly.
In this study, three new species of this genus are described from southern China.These three new species are fortunately easily distinguished from the already described species.A key to all known Chinese species and a map of distribution data are provided in this article.

Materials and methods
This study is based on specimens deposited in the Insect Collection of Guangxi Normal University, China.The examination of the specimens was carried out with a Leica M205A stereomicroscope.High-quality multifocused montage images were captured with a Leica DFC 450 digital imaging system.GPS coordinates were recorded from labels, references or estimated from Google Earth (http://earth.google.com/).Map was constructed using the software package ArcGIS version 10.2.All measurements are in millimeters.Standard measurements and indices are mostly as defined by Bolton (1975), with addition of ED and MSL as outlined below:

ED
Eye Diameter: maximum diameter of eye.

HL
Head Length: straight-line length of head in perfect full-face view, measured from the mid-point of the anterior clypeal margin to the midpoint of the posterior margin.In species where one or both of these margins are concave, the measurement is taken from the mid-point of a transverse line that spans the apices of the projecting portions.

HW
Head Width: maximum width of head in full-face view, excluding the eyes.

MSL
Mesosoma Length: diagonal length of the mesosoma in lateral view, measured from the point at which the pronotum meets the cervical shield to the posterior basal angle of the metapleuron.

PH
Petiole Height: height of petiole measured in lateral view from the apex of the ventral process (subpetiolar) vertically to a line intersecting the dorsalmost point of the node.

PL
Petiole Length: length of petiole measured in lateral view from the anterior process to the posteriormost point of the tergite, where it surrounds the gastral articulation.

PW
Pronotal Width: maximum width of pronotum measured in dorsal view.

SL
Scape Length: straight-line length of the antennal scape, excluding the basal constriction or neck.

TL
Total Length: total outstretched length of the individual, from the mandibular apex to the gastral apex.In full-face view head rectangular, longer than broad; posterior margin almost straight, posterior corner bluntly angular, lateral margin weakly convex.Mandible triangular, masticatory margin crenulate.Anterior margin of clypeus with convex to bluntly pointed median lobe.Antennal scape just slightly surpassing posterior corner of head, flagellar segments longer than broad.Eye small, with 10 ommatidia along maximum diameter, situated on midpoint of cephalic lateral margin.In lateral view occipital lamella of head forming a blunt triangular denticle.Dorsum of mesosoma strongly convex, promesonotal suture slightly impressed.Propodeum with short triangular denticle; propodeal declivity weakly concave close to tooth then relatively straight.Petiole roughly trapezoidal, about 2.1 times higher than long, dorsal and anterior margins weakly convex, posterior margin straight, subpetiolar process broadly triangular.Sting extruding.

Gnamptogenys dentihumera
In dorsal view anterolateral margin of pronotum with strong constriction, forming pointed denticle on humeral area.Metanotal groove ambiguously evident, evidenced by a change in sculpturing.Petiolar anterior corner rounded, lateral margin weakly convex in dorsal view.
Paratype workers (n = 12).TL 4. .General appearance as in holotype, with some specimens reddish brown to yellowish brown in color.We believe they are callow workers.
In lateral view occipital lamella of head forming blunt point.Dorsum of mesosoma convex.Promesonotal suture obvious.Petiole relatively thin, anterior margin convex, posterior margin straight, dorsal and anterior margin with no obvious boundary, subpetiolar process broadly triangular.Sting extruding.
In dorsal view anterior margin of pronotum rounded; metanotal groove distinct.Metanotum oval, very narrow, bordered by mesoscutellum and propodeum.Petiole anterior weakly rounded.
Habitat.This species was found nesting in deadwood of a branch on the ground in a subtropical evergreen broad-leaved forest, at the altitude of 925 m.All ants came from the same nest.
Etymology.This species is named from the Latin words "dent" (denticle) and "humer" (humeral), referring to the pronotum humeral area forming a pair of pointed denticles.
Differential diagnosis.The workers of G. dentihumera are similar to workers of G. panda, but G. dentihumera can be distinguished from the latter by propodeum with short triangular denticle and triangular subpetiolar process.The workers of G. dentihumera also resemble G. sinensis, but differ from the latter by the occipital lamella of head shaped as a blunt triangular denticle, and the pronotal humeral denticle of the workers of G. dentihumera is short, pointing laterally, unsurpassing the anterior margin of pronotum.In full-face view head trapezoid, longer than broad and widened posteriorly, posterior margin broadly concave, posterior corner rounded, lateral margin almost straight.Mandible triangular, masticatory margin crenulate.Anterior margin of clypeus with convex to bluntly pointed median lobe.Antennal scape just reaching posterior corner of head.Eye small, with 9 ommatidia along maximum diameter, situated on the midpoint of cephalic lateral margin.

Gnamptogenys nanlingensis
In lateral view posterior corner of head with small narrow, non-translucent lamella.Dorsum of mesosoma strongly convex.Promesonotal suture obvious.Propodeum without denticle, posterodorsal corner rounded.Petiole roughly trapezoid, about 2.25 times higher than long, dorsal margin weakly convex, anterior and posterior margin straight; subpetiolar process broadly triangular.Sting extruding.
In dorsal view pronotal humeral angle well-developed but not protuberant; lateral margin of pronotum almost straight, anterior margin convex, posterior margin concave.Metanotal groove inconspicuous.Petiole anterior corner rounded, posterior corner blunt.
Queen and male.Unknown.
Habitat.This species nests in deadwood of ranch on ground in subtropical evergreen broad-leaved forest, at the altitude of 1075 m.
Etymology.This species is named after its type-locality, "Nanling" National Nature Reserve of Guangdong Province, China.
Differential diagnosis.The workers of Gnamptogenys nanlingensis are easily distinguished from other Gnamptogenys by a combination of the following characters: large (HW≥1.44mm);pronotal humeral angle well-developed, but not forming denticle or spine; lateral margin of pronotum strongly convex, posterior margin concave; propodeum without denticle, posterodorsal corner rounded; pronotum, propleuron and propodeum, with strongly and irregularly rugulose; fourth abdominal tergite finely rugulose-punctate.
The workers of G. nanlingensis are morphologically similar to G. sichuanensis.However, in G. nanlingensis the subpetiolar process is triangular or cuneiform, while in G. sichuanensis the subpetiolar process is polygonal, with the anteroventral corner bluntly angular, the ventral margin concave, and the posteroventral corner rounded.G. nanlingensis has a narrow and inconspicuous occipital cephalic lamella, while the cephalic lamella of G. sichuanensis is well developed, but thin and almost translucent lamella.The fourth abdominal sternite in G. nanlingensis is reticulate-rugose, while in G. sichuanensis it istransversely striate.Holotype worker .TL 4.22, HL 1.05, HW 0.86, CI 82, SL 0.73, SI 84, ED 0.08, PW 0.71, MSL 1.31, PL 0.25, PH 0.61, DPW 0.50, LPI 244, DPI 200.In full-face view head rectangular, distinctly longer than broad, posterior margin almost straight, posterior corner nearly right-angular, lateral margin slightly convex.Mandible triangular, masticatory margin crenulate.Anterior margin of clypeus with convex to bluntly pointed median lobe.Antennal scape just reaching posterior corner of head, flagellar segments 3-7 broader than long.Eye very small, with 5 ommatidia along maximum diameter, situated on the midpoint of lateral cephalic margin.
In dorsal view humeral angle rounded; promesonotal suture visible; metanotal groove absent.In dorsal view petiolar node with approximate semicircular anterolateral margin, anterior margin convex and separated from lateral margin by weak blunt angle, lateral margin weakly convergent posteriorly, each margin weakly convex; posterior margin weakly concave; node about 1.5 times as long as broad; anterior petiolar corner rounded, posterior corner blunt.
Habitat.The specimens were found nesting under a stone in broadleaf forest and conifer mixed forest at the altitude of 1026 m.
Etymology.This species is named from the Latin words "quadrat" (quadrate) and "nodules" (petiole), referring to its nearly square petiole.
Differential diagnosis.The workers of G. quadrutinodules are distinguished from workers of other species of Gnamptogenys by the combination of the following characters: small eye, with 5 ommatidia along the maximum diameter; occipital lamella of head of head narrow and inconspicuous; petiole with anterior corner slight rounded and posterior corner bluntly angulate, node roughly sub-quadrate with dorsal and anterior margins weakly convex, posterior margin straight.Subpetiolar process sub-quadrate.
The workers of G. quadrutinodules are quite similar to those of G. coccina Zhou, 2001 andG. taivanensis (Wheeler, 1929).G. quadrutinodules can be distinguished from G. taivanensis by the rough rugose-punctate sculpturing of abdominal tergite III vs the diminished sculpturing on G. quadrutinodules, the shape of subpetiolar process seems different in the two species and the general color pattern for the workers also seems different.The distribution range of G. quadrutinodules may be sympatric with that of G. coccina ( Map. 1).Most of the specimens of G. coccina were collected from subtropical forests of Guangxi Zhuang Autonomous Region, China, and once recorded from Hubei province by Wang et al. (2009).So far the location of G. quadrutinodules, Jiangxi province, was not found the distribution of G. coccina.But Jiangxi, Guangxi and Hubei Provices compose triangle-distributed.So the G. coccina is likely to exist in Jiangxi, and which is impossible through distribution range to roughly distinguish G. quadrutinodules from G. coccina.So far G. coccina has not been found in sympatry with G. quadrutinodules but the present records suggest the likely presence of G. coccina in Jiangxi Province so assuming allopatry as as a rough sorting criteria for the two species is probably not a good idea.
However, the worker of G. quadrutinodules is distinguished from workers of G. coccina by the following characters: Promesonotal suture ambiguous; 3-7 flagellar segments broader than long; in lateral view petiole roughly sub-quadrate, in dorsal view petiole broader than long; subpetiolar process sub-quadrate.

Map 1 .
Figures 5-10.Gnamptogenys dentihumera paratype queen.5 head in full-face view 6 forewing in dorsal view 7 hindwing in dorsal view 8 gaster in dorsal view 9 body in dorsal view 10 body in lateral view.