A Newly Recorded Genus and Species , Harpagoxenus sublaevis , from China with a Key to the Known Species of Harpagoxenus of the World ( Hymenoptera : Formicidae )

The newly recorded genus and species to China, Harpagoxenus sublaevis (Nylander), is reported from Da Hinggan Ling, northeastern China. Diagnosis of the genus and description of the species are provided based on a Chinese specimen. A key to the 3 known species of the genus of the world is prepared based on the worker caste.


INTRODUCTION
The ant genus Harpagoxenus Forel, 1893, which is a very small genus in the subfamily Myrmicinae (Bolton 1994(Bolton , 1995) ) is distributed in the Palaearctic and Nearctic regions .Mayr (1861) established the genus Tomognathus based on the type-species Myrmica sublaevis Nylander, 1849.Later, Tomognathus Mayr, 1861, was recognized as a junior homonym of Tomognathus Agassiz, 1850, in the class Pisces.Therefore, Forel (1893) proposed Harpagoxenus as a replacement name for Tomognathus Mayr, 1861.Currently, only 3 valid species of Harpagoxenus Forel are recognized in the world.Myrmica sublaevis Nylander was the first species moved into the genus.The second species, Myrmica hirtula Nylander, was also moved into the genus, but has been revised as a junior synonym of H. sublaevis (Nylander) by Mayr (1861) and Radchenko (2007) respectively.The third species of the genus, H. canadensis, was described from Canada by M.R. Smith (1939) based on the queen, and the worker caste of the species was described by Gregg (1945) afterwards.The forth species of the genus, H. zaisanicus, was described from Mongolia by Pisarski (1963).In addition, a subspecies of the genus, H. sublaevis caucasicus, was described from Georgia by Arnol'di (1968).
In the ant species-diversity investigation of Da Hinggan Ling, northeastern China, the Palaearctic species, H. sublaevis (Nylander), was found in Mohe County, Heilongjiang Province.Both the genus and species are newly recorded in China, the genus and species are reported in this paper based on a Chinese specimen.A key to the 3 known species of the genus of the world is provided based on the worker caste.

MATERIALS AND METHODS
The worker caste of H. sublaevis (Nylander) was collected by the searchcollecting method.Descriptions and measurements were made under a XTB-1 stereo microscope with a micrometer.Illustrations were made under a Motic-700Z stereo microscope with illustrative equipment.
Standard measurements and indices are as defined in Bolton (1987), in addition, ED is included: TL-Total Length: The total outstretched length of the ant from the mandibular apex to the gastral apex.
HL-Head Length: The length of the head proper, excluding the mandibles, measured in a straight line from the mid-point of the anterior clypeal margin to the mid-point of the occipital margin, in full-face view.In species where the occipital margin or the clypeal margin is concave, the measurement is taken from the mid-point of a transverse line spanning the anteriormost or posteriormost projecting points, respectively.
HW-Head Width: The maximum width of the head in full face view, excluding the eyes.
CI-Cephalic Index = HW×100 / HL.SL-Scape Length: The maximum straight line length of the antennal scape excluding the basal constriction or neck close to the condylar bulb.
SI-Scape Index = SL×100 / HW.ED-Eye Diameter: The maximum diameter of the eye.PW-Pronotal Width: The maximum width of the pronotum in dorsal view.
AL-Alitrunk Length: The diagonal length of the alitrunk in profile view from the point at which the pronotum meets the cervical shield to the posterior base of the metapleuron.Diagnosis of worker: Body small.Head nearly rectangular.Mandibles broad, triangular to trapezoidal, outer margin roundly convex, masticatory margin edentate.Clypeus very short, without longitudinal carinae, the posteriorly extending portion broader the frontal lobes, anterior margin with paired hairs.Frontal carinae long, well surpassed eyes, antennal scrobes distinct, antennal insertions completely concealed by frontal lobes.Antennae short, 11-segmented, antennal clubs large, with 5 segments.Eyes developed, located slightly before the mid-points of the lateral sides of the head.Ocelli absent.Palpal formula 5, 3.In profile view, promesonotum relatively high, promesonotal suture reduced, metanotal groove shallowly depressed.Propodeum relatively low, with a pair of teeth or spines.Propodeal spiracles small and circular, close to anterior middle of the lateral sides.Propodeal lobes short, rounded apically.Metapleural gland bullae large, orifices rounded.Legs relatively short, ventral faces of femora longitudinally depressed, apices of hind tibiae without spurs.Basal tarsi about as long as the other 4 tarsi together.Claws simple.Petiole with developed erect node, without anterior peduncle, subpetiolar process usually developed.Postpetiolar node roundly convex, subpostpetiolar process tooth-like.Pilosity abundant.
In full face view, head rectangular, distinctly longer than broad.Occipital margin weakly concave, occipital corners rounded.Lateral sides nearly parallel, slightly convex behind eyes, and slightly concave before eyes.Mandibles trapezoidal, masticatory margins edentate.Clypeus without longitudinal carinae, anterior margin widely shallowly concave along the margin, anterolateral corners bluntly prominent.Frontal carinae weakly divergent backward, about as long as antennal scapes.Antennae 11-segmented, scapes concealable in the antennal scrobes; apices of scapes reach to 3/5 of the distance from antennal sockets to occipital corners; antennal clubs 5-segmented, decreased in segment length from apex to base.Eyes relatively large, located slightly before the mid-points of the lateral sides of the head.
Mandibles relatively smooth, very weakly finely punctured.Clypeus smooth and shining.Dorsum of head densely longitudinally striate, lateral sides of head sparsely longitudinally striate and densely finely punctured.Occipital margin and occipital corners smooth and shining.Alitrunk, petiole, and postpetiole densely finely punctured, interfaces appear as fine reticulations; in addition, dorsum of alitrunk finely longitudinally striate, dorsa of petiolar node and postpetiolar node sparsely transversely striate.Gaster smooth and shining.
Dorsa of head and body with abundant erect to suberect hairs and sparse decumbent pubescence.Antennal scapes and hind tibiae with sparse decumbent hairs and dense depressed pubescence.Color blackish brown.Mandibles, scapes, and legs brownish yellow.Gaster brownish black.
Discussion: The worker specimen from China conforms well to the original description and images of worker of H. sublaevis (Nylander) from Slovak (Antweb, CASENT 0178772, California Academy of Sciences).But with anterolateral corners of clypeus more prominent; in profile view, anterodorsal corner of pronotum more convex; propodeal lobes relatively narrower; anterodorsal corner of petiolar node bluntly prominent instead of roundly prominent; color comparatively darker.