﻿A contribution to the genus Didrepanephorus Wood-Mason, 1878 (Coleoptera, Scarabaeidae, Rutelinae)

﻿Abstract The diagnostic characters of the genera Didrepanephorus Wood-Mason, 1878 and Fruhstorferia Kolbe, 1894 are clarified. The following nomenclatorial acts are proposed: Didrepanephorusbirmanicus (Arrow, 1907), comb. nov., Didrepanephorusfukinukii (Muramoto & Araya, 2000), comb. nov., Fruhstorferiabaron (Prokofiev, 2013), comb. nov., and Fruhstorferiaanthracina Ohaus, 1903, comb. rev.Didrepanephorustangzhaoyangi Zhao & Liu, sp. nov. is described from Yunnan Province, China. A lectotype is designated for Fruhstorferiabirmanica Arrow, 1907. Didrepanephorusmizunumai Nagai & Hirasawa, 1991 is reported from Myanmar for the first time.


Introduction
The subtribe Didrepanephorina was established by Ohaus (1918) to accommodate a morphologically remarkable genus Didrepanephorus Wood-Mason, 1878. The type species of this genus, D. bifalcifer Wood-Mason, 1878, is a densely setose ruteline beetle with strong sexual dimorphism in the shape of mandibles (Wood-Mason 1878).
The morphological affinities between Didrepanephorus and Fruhstorferia Kolbe, 1894 had resulted in a chaos of generic separations when different characters were referred: Arrow (1917) separated Fruhstorferia from Didrepanephorus mainly by the dorsal surface generally without dense setae. Ohaus (1934a) recognized Didrepanephorus species by the complete frontoclypeal suture and reassigned species of the two genera. Young (1999) took the orientation of mandibles into account, i.e., bent upward in Didrepanephorus but directed forward in Fruhstorferia. Most recently, Muramoto (2005) differentiated the two genera by the prosternal process and abbreviation of abdominal ventrites 1-4 in males. Besides, some authors questioned the separation of the two genera (Nagai and Hirasawa 1991;Qiu et al. 2021). The authors of the present paper had found reliable morphological characters to distinguish the two genera. Based on these characters, the delimitation of the two genera is herein clarified.
The Chinese Didrepanephorus species are still poorly known. Qiu et al. (2021) described a new species from Guizhou and recorded two species new to Chinese fauna. Their biology was also reported, which greatly improved the knowledge of this genus. During the taxonomic study of the Old World Rutelini, a new species similar to D. ohbayashii (Nagai, 2004) was received by the first author from Yunnan Province of China. Additionally, based on the examination of the type material of F. birmanica Arrow, 1907, some taxonomic problems are also solved herein.

Material and methods
Images of the external characters and male genitalia were taken using a Canon EOS 760D camera in conjunction with a Tamron 90 mm f/2.8 1:1 Macro Lens and a Laowa 25 mm f/2.8 2.5-5X Ultra Macro Lens, respectively. Zerene Stacker (version 1.04) was used for stacking. All images were modified and arranged in plates in Adobe Photoshop CS5.
Data of material in NHMUK are cited verbatim. Different labels are separated by a double slash (//). Specimens studied in this research are deposited in the following public and private collections:
The authors of the present paper tentatively delimitate the two genera based on the shape of the male mandible and the range of body length. Regarding the Didrepanephorus species, there is a prominent protrusion at the base of lower margin of male mandible, which is either sharp or blunt at apex, and the lower margin is concave or strongly concave before the protrusion. Such prominent protrusion is replaced by a weak lump in Fruhstorferia, with exception of F. flavipennis Nagai, 1984, in which the lump is acute at apex. But the lower margin is never concave before the protrusion in Fruhstorferia. Sometimes there is a basal protrusion also at upper margin of mandible in Didrepanephorus species, which is absent in all Fruhstorferia species. The mandible of Didrepanephorus bent upwards, but directed forward in Fruhstorferia. The body length of Didrepanephorus varies from 13.0-22.4 mm in males (mandibles excluding) and 13.5-23.2 mm in females (Nagai and Hirasawa 1991;Muramoto and Araya 2000;Muramoto 2003bMuramoto , 2005Muramoto , 2013Qiu et al. 2021). In the genus Fruhstorferia, the range is 22.0-31.1 mm in males (mandibles excluding) and 23.0-30.0 mm in females (Nagai 1984(Nagai , 1989Ohaus 1903;Prokofiev 2013). The range of body length is almost not overlapped and the genus Fruhstorferia is generally longer. At this stage, authors are unable to provide diagnostic characters of females due to lack of material.
The following nomenclatorial acts can be proposed based on the above delimitation: D. birmanicus (Arrow, 1907), comb. nov., D. fukinukii (Muramoto & Araya, 2000), comb. nov., F. baron (Prokofiev, 2013), comb. nov. and F. anthracina Ohaus, 1903, comb. rev. Prokofiev (2013 transferred F. anthracina to the genus Didrepanephorus because of the strongly abbreviated abdominal ventrites 1-4 in male. In the same paper, Prokofiev described a new species, i.e., D. baron and assigned it to the genus Didrepanephorus for the same reason. The two species lack basal protrusion at the lower margin of male mandible and have body longer, therefore they should be placed in the genus Fruhstorferia. The placement of D. takuyai (Muramoto, 2003) is still unclear: the male of this species has upright mandible without protrusion or lump at base of lower margin, and the body length of male can reach 23.5 mm (Muramoto 2003a). Consequently, a checklist of the two genera is provided (Table 1). Only type localities are cited to avoid probable misidentifications.

Didrepanephorus tangzhaoyangi
Head. Dorsal surface yellowish brown, marginal portions darkened. Clypeus flat, trapezoidal, anterior margin nearly straight, anterior corner obtusely right-angled, side strongly convergent anteriad and weakly swollen in basal two fifth, then roundly curved, and almost subparallel in apical half; punctures large at disc but absent in middle, punctures small at marginal portions. Frontal-clypeal suture broadly interrupted medially, black at each side. Frons and vertex with scattered large punctures. Eyes canthus with roundly curved outer margin, not extends beyond outermost point of eye. Antenna reddish brown, length of antennal club distinctly shorter than antennomeres 2-7 combined. Dorsal surface of head with moderately dense, erect long setae, broadly glabrous medially. Labrum blackish brown, strongly exposed dorsally, with dense, erect long setae along margin, anterior margin feebly sinuate. Mandible blackish brown, bends upward, upper margin with a large, acute basal protrusion and a small, blunt proximal protrusion, lower margin with a large protrusion at base. Maxilla and maxillary palp reddish brown, maxilla with dense and long setae. Mentum yellowish brown, apical fourth of mentum darkened and slightly swollen, anterior margin curved but strongly concave medially, surface with sparse short setae each emerging from a puncture.
Pronotum. Orange-brown, darkened at anterior and posterior margins. Strongly convex, ca. 1.46 × as wide as long, widest near middle. Anterior margin bisinuate; anterior marginal membrane complete. Sides feebly convergent posteriad in posterior half, roundly and broadly curved at middle, then strongly convergent anteriad in anterior half. Posterior margin broadly protruding in middle. All marginal lines complete. Anterior angle weakly protruding, posterior angle round. Surface with sparse large punctures, somewhat aggregate and smaller at disc. Each dorsal puncture accommodates a minute seta; lateral margin with a row of erect short setae. Scutellum. Brown, margin blackish brown. Semicircular in shape. Surface with sparse punctures, impunctate medially.
Elytra. Dark orange-brown. Convex, length of each elytron slightly longer than cross width of the two elytra. Surface uneven, humeral and apical umbones weakly prominent. Strial punctures large and deep, punctures on primary striae as large as punctures on secondary striae, 1 st primary stria well defined by a longitudinal row of regular punctures, other striae unrecognizable; the whole surface with sparse small punctures, denser on lateral portions. Surface with moderately dense, semierect short setae, denser apically. Epipleura with a row of dense, short to moderately long setae.
Propygidium and pygidium. Brown, disc and apical portions of pygidium yellowish brown. Surfaces with moderately dense small punctures and erect, short to moderately long setae. Pygidium strongly convex and curved to ventrum, apex with a short row of erect long setae.
Ventral thoracic surface. Ventral prothoracic surface yellowish brown, dark brown around procoxal cavity; surface with moderately dense, erect long setae, each emerging from a small puncture; anterior margin with a row of dense and very long setae. Prosternal process gradually narrower toward apex, with very dense, erect long setae. Ventral mesothoracic surface dark brown, with scattered small punctures; a broad mid-  (Arrow, 1907) (Lectotype of Fruhstorferia birmanica Arrow, 1907),oblique lateral view, photo © Keita Matsumoto (NHMUK) 9-10 male genitalia of holotype of D. tangzhaoyangi 9 dorsal view 10 ventral view. Scale bar for genitalia only. dle portion smooth and glabrous, with an oblique row of small punctures at each side; each puncture with a recumbent short seta. Ventral metathoracic surface yellowish brown, gradually darkened toward each side; with dense small punctures and very long setae, less setose medially.
Abdominal ventrites. Dark brown, ventrites 2-4 yellowish brown between anterior and posterior margin. Ventrites 1-4 strongly abbreviated; ventrite 6 strongly concave apically. Surface with the following arrangements of small punctures: moderately dense at medial portions of each ventrites, moderately dense and forming a row at each side near posterior margin of ventrites 1-5, sparse at each side of ventrites 1-5. Each puncture with a semierect short seta, which become moderately long to long at marginal portions and sides.
Fore legs. Yellowish brown; joints of trochanter, femur, and tibia, including protibial spur and teeth dark brown; protarsus and claws blackish brown. Protibia tridentate, apical and proximal teeth sharp at apices; third tooth shorter and blunter, more spaced from the two anterior teeth. Protarsus strongly thickened, the weakly protruding ventrolateral apex of protarsomere 4 with a small spiniform seta at each side, protarsomere 5 with a small and blunt internomedial protuberance. Protarsal claws strongly bent, unsplit at apices, inner one distinctly larger than the outer one. Empodium with one long seta. Protibial notch distinct. Dorsal surface of protibia with dense, erect short setae at inner half.
Middle and hind legs. Yellowish brown; joints of trochanters, femora, and tibiae (base) pale reddish brown; apex of tibial spurs, as well as tarsi and claws reddish brown. Mesotibia with two sharp teeth at apex, the upper one smaller. Metatibia with an apically subtruncate ramus at apex, the ridge with several small teeth. Base of the sharply protruding ventrolateral apices of tarsomeres 4 with a large spiniform seta at each side; tarsomeres 5 with a large and sharp internobasal protuberance. Outer mesotarsal claws widely and deeply split at apex and forming two branches, upper branches slightly thinner and sharper, that of hindlegs also longer than the lower one; inner tarsal claw simply sharp at apex. Empodium of mesotarsus with one long seta, of metatarsus with two long setae. Femora and inner surface of tibia with dense and very long setae, tibia with dense, semierect, and moderately long setae.
Male paratypes. Most specimens consistent in morphological features, small-sized male (Fig. 4) has distinctly shorter mandible with proximal tooth absent, pronotum narrower and less convex (1.41 × as wide as long).
Female paratypes (mainly based on individual of Figs 5, 6, with modification based on variability of paratype series). General. Body more elongated ovoid than male, coloration similar to male.
Head. Clypeus flat, subtrapezoidal (posterior margin ca. 3 × wider than anterior margin), anterior margin weakly sinuate and distinctly reflexed, anterior corner broadly rounded, side strongly convergent anteriad and weakly swollen in basal two fifth, then roundly curved, and strongly convergent anteriad to anterior corner; punctures large and almost not spaced. Frontal-clypeal suture formed by a sinuate row of large and not spaced punctures. Frons and vertex with irregular large punctures in anterior half, punctures smaller at inner side of eye. Mandible reddish brown, short, anterior edge strongly reflected with two apically blunt teeth, outer edge weakly concave medially and convex basally. Anterior margin of mentum distinctly bilobed. Antennomeres 3-7 somewhat abbreviated.
Pronotum. Pronotum less convex than male, ca. 1.51 ×as wide as long, anterior margin strongly bisinuate; sides feebly convergent anteriad in posterior half, roundly and broadly curved at middle, then strongly convergent anteriad and feebly concave in anterior half; anterior angle distinctly protruding, posterior angle round.
Scutellum. Scutellum more triangular than male. Elytra. Elytral surface less uneven compared to male, with irregular and vague longitudinal costae; lateral portion of elytron distinctly bulging behind midpoint; punctures sparser.
Legs. Procoxae situated closer. Three teeth of protibia almost equal in size and shape, not very sharp at apices. Protarsus not thickened, base of the sharply protruding ventrolateral apices of protarsomere 4 with a large spiniform seta at each side, protarsomere 5 without internomedial protuberance. Protarsal claws less bent than in male, two claws almost equal in size; the inner protarsal claw widely and deeply split into two branches, the lower branch is a small dent at middle of inner protarsal claw. Empodium of protarsus with two long setae. Dorsal surface of protibia with sparser setae formed in rows. Metafemur thicker than in male. Protibia and mesotibia feebly curved inward.
Differential diagnosis. The new species is most similar to Laotian D. ohbayashii (Nagai, 2004), but the large-sized male of the new species has distinctly shorter mandibles. The large and acute basal protrusion is absent in upper margin of mandible in male of D. ohbayashii. The parameres of the two species are basally fused and strongly asymmetric. However, the parameres of D. tangzhaoyangi differ as follows: the left paramere without an incision at outer margin, apex of the left paramere distinctly narrower, the right paramere strongly curved outward proximally (orients apically in D. ohbayashii). The female of D. ohbayashii has more concave outer edge of mandible.
Etymology. The specific epithet is dedicated to Zhao-Yang Tang, who generously provided most of the type material of the new taxon.
Distribution. China (Yunnan: Dehong Prefecture). (Arrow, 1907) Arrow, 1907: Nagai 1984. Remarks. The taxon Fruhstorferia birmanica was originally described based on a pair of specimens from Ruby Mines, Burma (Arrow 1907). The lectotype has not yet been designated and the male illustrated by Muramoto and Araya (2000) has been erroneously fixed as holotype. According to Art. 74.7.1 (ICZN 1999), both specimens should be regarded as syntypes. The examination of both syntypes reveals that the female is conspecific with D. mizunumai Nagai & Hirasawa, 1991. Therefore, a lectotype designation is necessary.

Didrepanephorus birmanicus
The male genitalia of the lectotype (Figs 8, 11-15) is partly damaged, which greatly complicates the comparison to its related species. However, the similarity of this species to small-sized male of D. yunnanus (Ohaus, 1911) is still apparent in many external features, especially in the allied shape of terminal segment of maxillary palp, which is more expanded and compressed than other Didrepanephorus species. There is a strong concavity at the base of lower margin of mandible. The protrusion at lower margin is partly hidden under the labrum. These characters match the above definitions for Didrepanephorus. Thus, this species is transferred to the genus Didrepanephorus herein. Among the five subspecies of D. yunnanus, i.e., D. y. yunnanus (Ohaus, 1911), D. y. clermonti Benderitter, 1929, D. y. piaoacensis Nagai, 2004, D. y. wakaharai Nagai, 2004, and D. y. kachinensis Muramoto, 2005, recognized by Muramoto (2005, D. y. kachinensis appears to be most similar to D. birmanicus due to the generally reddish brown body in combination to the closest geographical distance. To fully understand the relation between the two species, examination of topotypical specimens of D. birmanicus with undamaged male genitalia is needed. This species was partly misinterpreted and the name was previously applied to two different species (see below). This species is so far only known from the lectotype.
Remarks. This species is transferred to the genus Didrepanephorus here because of the distinct basal protrusion at the lower margin of mandible, as shown by Nagai and Hirasawa (1991).
Judging from the figures of habitus and male genitalia, the records of F. birmanica from Northwest Thailand (Nagai and Hirasawa 1991;Nagai 2004) are considered as D. fukinukii here. Thus, the record of F. birmanica in Thailand should be omitted. Arrow (1917Arrow ( , 1919 and Muramoto and Araya (2000) partly misinterpreted the taxon F. birmanica and applied the name to a species from Chin Hills. The species from Chin Hills appears to be very similar to D. fukinukii but having different male genitalia, which has strong incision at outer margin of left paramere.

Didrepanephorus mizunumai Nagai & Hirasawa, 1991 Figs 16-18
Fruhstorferia birmanica Arrow, 1907: Arrow 1907  Remarks. The female of D. mizunumai is easily characterized by the three strongly elevated costae between humeral and apical umbone, as well as a bulge on lateral portions of elytron. The paralectotype of F. birmanica (Figs 16-18) well fits topotypical female of D. mizunumai from Fang. Therefore, the female paralectotype represents a new distributional record for Myanmar. Two similar species, i.e., Laotian D. lao Nagai, 2005 and Vietnamese D. zen Muramoto, 2009 have minor morphological differences, but both are more restricted in their known distribution ranges.

Discussion
In this study, we propose a new delimitation for Didrepanephorus and Fruhstorferia, which temporarily solves those taxonomic conflicts at generic level. But the placement of D. takuyai (Muramoto, 2003) remains uncertain and this species requires further examination. Type material of five of the seven taxa of the genus Didrepanephorus described before 2000 had been re-examined and illustrated (Muramoto and Fujioka 2000;Muramoto 2005;Qiu et al. 2021; the present paper). Species described in this century were all well-illustrated. Hence there is a good taxonomic fundament at specific or infraspecific level. To date, the genus Didrepanephorus comprises 21 valid taxa distributed in the Indochina Peninsula, southern China, and the Himalaya. Two thirds of the valid taxa were described in this century and it is likely that new species will be discovered in the future. The Chin Hills species similar to D. fukinukii should be studied to ensure its status. The registered Chinese fauna of Didrepanephorus increased rapidly from two to six species within two years. New faunistic records can be expected due to the existence of other congeners known from the adjacent regions.
Moreover, no phylogenetic analysis was conducted for Didrepanephorus and related genera, i.e., Fruhstorferia, Kibakoganea, Masumotokoganea, Nagainokoganea and Pukupuku. In the morphology-based phylogenetic study (Jameson 1997), D. mizunumai and K. sexmaculata were used as representatives of the subtribe Fruhstorferiina Ohaus, 1918 and formed a clade together with the genera Ceroplophana Gestro, 1893, Dicaulocephalus Gestro, 1888 and Peperonota Westwood, 1847, which were traditionally recognized as members of the subtribe Parastasiina Burmeister, 1844 (Ohaus 1918(Ohaus , 1934b. It suggests that these three genera should be taken into consideration as well.