The genus Diplocheila Brullé, 1834 in Cambodia, with descriptions of two new species (Coleoptera, Carabidae, Licinini)

Abstract The Diplocheila species recorded from Cambodia are discussed and two new species, Diplocheila walterrossiisp. nov. and D. erwinisp. nov. are described. Moreover, the holotypes of D. laevigata (Bates, 1892) and D. laevigotoides Jedlička, 1936, two often misinterpreted species from the Oriental Region, are illustrated and some aspects of their morphology are clarified. Finally, an analytical key to all species recorded from Cambodia is provided.


Introduction
The carabid fauna of Cambodia is still poorly known. Only 172 species belonging to the family Carabidae are recorded from this Asian country to date (Choi et al. 2019;Anichtchenko et al. 2020), and very few systematic studies have been devoted to this The type locality is quoted in the original label form.
Apparent body length (ABL) is measured from the apex of labrum to apex of the longer elytron. PW: pronotum width at the widest point; PL: pronotum length measured from the apical to basal margin along midline; EW: elytral width at the widest point; EL: elytra length from the base of scutellum to apex of the longer elytron; LR: ratio of the length measured between the straight line connecting the apices of lateral lobes of the labrum and narrowest point of medial emargination (a) and the length measured between the straight line connecting the apices of lateral lobes of the labrum and frontoclypeal suture (b) (Fig. 1).
Digital images were taken using a Leica DFC295 camera mounted on a Leica M205 C stereomicroscope and using Leica Application System v. 4.0 software.

Taxonomy
The systematic arrangement of Diplocheila is still unclear. In particular, the attribution of the species to subgenera is still under discussion, as well as the validity of the subgenera (Will 1998). Ball (1959Ball ( , 1966Ball ( , 1992 first proposed a comprehensive classification of world species into subgenera (Diplocheila s. str., Neorembus Ball, 1959 andIsorembus Jeannel, 1949); moreover, he recognized two species groups within Diplocheila s. str. (polita and daldorfi groups) and three inside Isorembus (aegyptiaca, striatopunctata, and zeelandica groups). Lorenz (2005), in the list of extant ground beetles of the world, referred to the arrangement by Ball (1959), but with a different subdivision of species into subgenera; Lafer and Kataev (2008) accepted Ball's approach in the subdivision of species but proposed to reinstate the subgenus Submera Habu, 1956, which had been treated by Ball (1959) as a synonym of Isorembus; in the same way, Huber and Marggi (2017), in the recent catalogue of Palaearctic Coleoptera, reinstated the subgenus Submera as valid, following a different subdivision of species compared to Ball's arrangement. Unfortunately, the classifications proposed by the catalogues of Lorenz (2005) and Huber and Marggi (2017) lack authors' comments explaining their treatment. In this context, we prefer to follow Ball's arrangement as the most justified, but we ac- cept the proposal by Lafer and Kataev (2008) to retain valid the subgenus Submera for Diplocheila laevis (Lesne, 1896).
In the material collected by Walter Rossi in Cambodia we have identified:  Jhansi District, Babina, VIII.1987 (CGi).
Remarks. Diplocheila latifrons is the only species belonging to subgenus Neorembus. Two subspecies are known: the nominotypical one, which is widely distributed across China, Korea, Japan, India, Myanmar, the Russian Far East, Vietnam, Laos, Cambodia, Thailand and Indonesia, and the ssp. darlingtoni Ball, 1959, which is only recorded from the Philippines (Andrewes 1922;Ball 1959).

Diplocheila
Remarks. Diplocheila laevigata is recorded from southern China, Myanmar, Vietnam, Laos, and Cambodia (Andrewes 1922;Ball 1959;Lafer and Kataev 2008). Unfortunately, the male HT in the Fea Collection at MCSNG is an immature specimen ( Fig.  2) with a scarcely chitinized aedeagus (Fig. 26); however, its examination, made possible thanks to the courtesy of the Honorary Curator Roberto Poggi, revealed that it was conspecific with the specimens from Cambodia (Figs 8,14,27). An aedeagus of D. laevigata, substantially corresponding to the HT, is also illustrated by Lafer and Kataev (2008).
Two specimens from Thailand deposited in CGi (2 ♂♂, Chiang Mai, 6.V.1988, R. Sciaky det.; Figs 9, 15) show a similar aedeagal morphology but pronotum and labrum are differently shaped compared to the HT and to the specimens from Cambodia; they could belong to a new species, but it is not described here, awaiting more abundant material. A further specimen from Thailand deposited at BMNH (1 ♀, Bangkok, Larnaudie leg., H.E. Andrewes Coll.) probably belongs to a different, new species.
A male specimen from Indonesia deposited at BMNH (1 ♂, Indes Neerl., Boucard leg., H.E. Andrewes Coll.) differs from the D. laevigata HT not only in external morphology, but also in the shape of the aedeagus (although this is damaged, the api-cal lamella appears to be clearly different); its external morphology does not match D. laevigotoides HT either, in spite of the opinion of Lafer and Kataev (2008) that the records of D. laevigata from Indonesia, together with those from Japan and the Philippines, are probably instead D. laevigotoides. Therefore, this specimen also likely belongs to a new species, awaiting description when more abundant material becomes available.   (Fig. 3).
Remarks. Diplocheila laevigotoides has often been confused in the past with D. laevigata; for this reason, although the species is probably not present in Cambodia, we decided to examine and illustrate the habitus of the HT specimen (Fig. 3) deposited at BMNH, in order to examine some aspects of its morphology and clarify possible misunderstandings. For this reason, the species is also included in the identification key to the species of Cambodia (see below). Unfortunately, the HT is a female specimen (and the unique PT specimen found by Jiří Hájek in Jedlička Collection at NMPC is also a female). Nevertheless, its habitus and the particular shape of the pronotum and labrum allow for D. laevigata and D. laevigotoides to be reliably distinguished. The opinion of Lafer and Kataev (2008) that the records of D. laevigata from Indonesia could refer to D. laevigotoides is not confirmed by our examination of a male specimen from the same area (see Remarks under D. laevigata). We have nothing at present to add about the records from Japan (Habu 1959) and the Philippines (Ball 1959), which are also suspected to belong to D. laevigotoides.
It is curious that this species was described by Jedlička (1936) as D. laevigotoides (probably a printing error), although the label of the HT reports "laevigatoides" (Fig. 3).   sexsetose labrum, it is easily distinguished from D. erwini sp. nov. by the larger body size (15-18 mm vs 12-14 mm), from D. laevigata and D. laevigotoides by the more transverse pronotum (PW/PL = 1.38 vs 1.28-1.32), from D. indus by the hind angles of pronotum not protruding (externally protruding in D. indus) and from all these species by the morphology of the aedeagus.
Head: almost quadrangular, robust, glabrous except for the supraorbital setae. Eyes markedly convex; a single supraorbital seta on each side. Dorsum with microsculpture not evident, only with scattered punctures visible at >100× magnification; frontal impressions short and superficial. Labrum symmetrically and deeply (LR = 0.72) emarginate, with six setigerous punctures on anterior margin (4 medial equidistant + 2 lateral on lobes). Clypeus trapezoid, distinctly concave anteriorly, with 1 seta at each anterolateral corner. Antennae moderately long, densely pubescent from segment 4, with terminal two articles surpassing base of pronotum; segments elongate, the second one short, as long as a half of first. Mandibles elongate, broad, approximately similar to one another (the left with apical cutting edge more concave), with scrobe well-defined and glabrous and apex blunt; terebral tooth triangular and prominent. Labial and maxillary palps fusiform, with apices narrowly truncate.
Thorax: pronotum smooth, with very faint isodiametric microsculpture evident at >200× magnification and with scattered punctures, transverse (PW/PL = 1.38), widest just above middle (Fig. 10). Disk moderately convex. Sides moderately rounded in anterior half, delicately sinuate backwards. Hind angles rounded obtuse, with a posterolateral seta. Posterior margin rectilinear between basal impressions, which are linear and markedly impressed; anterior margin with front angles nearly obsolete. A single lateral seta on each side at anterior third. Lateral bead continuous, separated from the discal area by a narrow groove, only scarcely dilated before hind angles. Medial longitudinal impression fine, nearly reaching anterior and posterior margins; anterior transversal impression absent.
Ventral surface (thorax and abdomen): prosternum and proepisterna glabrous and impunctate (only with very fine punctures). Metepisterna twice as long as their width at anterior side; metepimera narrow, nearly rectangular. Prosternal intercoxal process parallel-sided with blunt apex, delicately bordered. Abdominal ventrites IV-VI shiny but shagreened at sides, glabrous except one pair of subapical central setae; males with 2, females with 4 setae at apex of ventrite VII.
Head: almost quadrangular, glabrous except for the supraorbital setae, narrow in comparison with pronotum. Eyes markedly convex; a single supraorbital seta on each side. Dorsum with microsculpture not evident, only with scattered punctures visible at >100× magnification; frontal impressions short and superficial. Labrum symmetrically and deeply (LR = 0.78) emarginate, with six setigerous punctures on anterior margin (4 medial equidistant + 2 lateral on lobes). Clypeus trapezoid, distinctly concave anteriorly, with 1 seta on each side at anterolateral corner. Antennae moderately long, densely pubescent from segment 4, with terminal 2 articles surpassing base of pronotum; segments elongate, the second one short, as long as a half of first. Mandibles elongate, broad, approximately similar each another (the left with apical cutting edge more concave), with scrobe well-defined and glabrous and apex blunt; terebral tooth triangular and prominent. Labial and maxillary palps fusiform, with apices narrowly truncate. Thorax: pronotum smooth, with very faint microsculpture evident at >200× magnification and with scattered punctures, subquadrate (PW/PL = 1.18), widest at middle (Fig. 11). Disk moderately convex. Sides from rectilinear to hardly rounded in anterior half; rectilinear or very slightly sinuate backwards. Hind angles rounded obtuse, provided with a postero-lateral seta. Posterior margin rectilinear between basal impressions, which are linear and markedly impressed; anterior margin with front angles nearly obsolete. A single lateral seta on each side just above middle. Lateral bead continuous, separated from the discal area by a narrow groove, only scarcely dilated before hind angles. Medial longitudinal impression fine, nearly reaching anterior and posterior margins; anterior transversal impression absent.
Ventral surface (thorax and abdomen): prosternum and proepisterna glabrous and impunctate (only with very fine punctures). Metepisterna as long as twice the width of anterior side; metepimera large, broadly rounded. Prosternal intercoxal pro- cess widely rounded and bordered at apex. Abdominal ventrites IV-VI shiny but shagreened at sides, glabrous except one pair subapical central setae; males with 2, females with 4 marginal setae at apex of ventrite VII.
Legs: moderately slender. Posterior face of femora with 1 seta in profemora, 2 in mesofemora and metafemora. Metatrochanters glabrous and slightly shorter than half length of metafemora. Protibial antennal cleaning organ well developed, with 2 clip setae. Protibiae robust, with 4 or 5 outer apical spines; mesotibiae with a group of setae at middle of inner face; metatibiae longitudinally furrowed at inner face. Dorsal face of tarsomeres smooth. Male protarsomeres 1-3 distinctly dilated, slightly asymmetrical; meso-and metatarsomeres not dilated in both sexes; tarsomere 5 ventrally glabrous, dorsally with 2 apical setae; claws smooth.
Male genitalia: median lobe of aedeagus short and markedly swollen before apex in lateral view (Fig. 23); the apical lamella shortly triangular in dorsal view, with blunt  Etymology. This species is named, as a token of our esteem, after our late colleague Terry Erwin, a world-renowned specialist in world and tropical Carabidae.
Distribution and ecology. Geographical distribution: this species is recorded only from the extreme south banks of the Tonle Sap Lake, Kampong Chhnang Province, Cambodia. It seems to have a more restricted distribution than D. walterrossii sp. nov., which has been recorded from the same site as well as from other two localities in north-western Cambodia (Fig. 33). Life habits: the specimens of the type series were collected on lake banks by light trapping. No other data are available.
Remarks. It is difficult to assess the closest relatives of D. erwini sp. nov. It belongs to the D. polita group (sensu Ball 1959), as it shares the characters distinguishing this group and, moreover, its aedeagus is very similar to that of D. polita (see pl. V, fig. 72a in Ball 1959). Diplocheila erwini sp. nov., on the other hand, is easily distinguished from D. polita which has a quadrisetose labrum and pronotum more transverse (PW/ PL = 1.31 according to Fig. 26 in Plate II in Ball 1959), as well as a larger body size (ABL = 13.4-18.4) (Ball 1959).

Conclusions
Seven species of the genus Diplocheila are currently known from Cambodia. Two new species (D. erwini sp. nov. and D. walterrossii sp. nov.) are here added to its fauna, and D. laevis is recorded for the first time from this country. As the adults are macropterus and probably good fliers, no species are likely steno-endemic, although D. erwini sp. nov. and D. walterrossii sp. nov. are only known from Cambodia to date. The discovery of a new species (D. walterrossii sp. nov.) with external morphology very similar to D. laevigata drove us to study and compare D. laevigata and D. laevigotoides, which were often misunderstood and misidentified in the past. The examination of the holotypes of these species confirmed their validity and the status of D. walterrossii sp. nov., providing new morphological information useful for the correct identification of the three taxa. Finally, the study of various specimens from countries of the Oriental Region other than Cambodia convinced us of the possibility of additional new species, similar to D. laevigata in external morphology and therefore confused with it in the past, awaiting discovery and description.