Five new species of the leaf-beetle genus Monolepta Chevrolat (Coleoptera, Chrysomelidae, Galerucinae) from China

Abstract In this study, five new species of the leaf-beetle genus Monolepta Chevrolat, 1836 (Coleoptera, Chrysomelidae, Galerucinae) are described from China: M.albipunctatasp. nov., M.alticolasp. nov., M.bivittatasp. nov., M.mengsongensissp. nov., and M.rubripennissp. nov. A key and catalogue to the 68 Chinese species of Monolepta with the second and third antennomeres of equal length are given as well as photographs of the habitus and aedeagus of the new species and type habitus images of 37 known species.


Introduction
With 708 species and six subspecies distributed worldwide (Nie et al. 2017), the leaf-beetle genus Monolepta is one of the largest genera in Galerucinae (Coleoptera, Chrysomelidae). There are 342 species distributed in the Oriental region, which is almost half the species in this genus. Several new Chinese species have been described since revision (Gressitt and Kimoto 1963) and 73 species have been recorded, 71 in the Oriental region and two in the Palaearctic region (Yang et al. 2015).
During sorting of specimens in the Institute of Zoology, Academy of Sciences, five new species were found and are described here. In addition, photographs of the habitus, external parts and aedeagus of the new species and habitus of known species (in Suppl. material 1) are also given together with a key to the Chinese species.

Material and methods
The specimens were examined with an Olympus SZ61 microscope.

Dissections
The abdomen was taken from the specimens, then transferred to a vial containing 5% NaOH solution and heated in boiled water around 5-7 minutes. The abdomen with aedeagus was washed in distilled water 3 or 4 times, transferred into a cavity slide using fine forceps and the aedeagus was separated by hooked minute-pin dissecting needles.

Photographs
Habitus images were taken using a Canon 5DSR digital camera, equipped with a lens EF 75-300 mm f/4-5.6 linking a Nikon CFI Plan Apochromat Lambda 4× or 2× objective lens. Illumination was by flash, and each photo was taken by a macro slide system. Aedeagus images were taken using a Nikon D610 digital camera, linking a Zeiss V microscope, with 5× and 10× objective lens. A cable shutter release was used to prevent the camera from shaking. The number of images taken was depending on the size of the aedeagus.

Labels
The label data is translated into English from the original Chinese.

Type depository
Type specimens of the five new species are deposited in the Institute of Zoology, Chinese Academy of Sciences, Beijing, China (IZAS). l en gth of the 1st segment of the hind tarsi which is longer than the remaining combined segments in D. humeralis Jacoby, 1903, the type species. Konstantinov (2002) synonymized Aemulaphthona Scherer, 1969, originally placed in Alticini, based on several characters of the type species Aemulaphthona ochracea (Weise, 1922), such as the flat head in lateral view, absence of a supraorbital sulcus, and metafemur without a metafemoral spring. Wagner (2007) synonymized Chimporia Laboissière 1931 based on the similarity of the aedeagus. Also, based on characters of the anterior coxae and the second antennomere, and morphology of aedeagus, many new genera were described for species previously included in Monolepta, such as Afromaculepta Wagner, 2000, Afromegalepta Wagner, 2001, Afrocandezea Wagner, 2002, Afronaumannia Wagner, 2005, Monoleptoides Wagner, 2011, Neobarombiella Wagner, 2012, Orthoneolepta Hazmi & Wagner, 2013, Paraneolepta Hazmi & Wagner, 2013, Bicolorizea Wagner, 2015, and Doeberllepta Wagner, 2017 The ratio of antennomeres 2 and 3 is of great importance for the identification in Monolepta and related genera. The length of 2 to 3 in the type species, M. bioculata, is 0.83-1.00 (Wagner 2007). Sometimes antennomere 2 is slightly shorter than 3, as in M. jeanneli (0.78-0.87), or on the contrary, antennomere 2 is slightly longer than 3, as in M. usambarica (1. 00-1.20;Wagner 2000). In general, the ratio of antennomeres 2 and 3 is 0.80-1.20.
There are also some similar genera in the Oriental region. In Arcastes, the lack of pronotal depressions and the significantly enlarged antennomeres 3-8 distinguishes it from other genera, as does the ratio of antennomeres 2 and 3, which is 0.5-0.57; thus, it is easily recognized from Monolepta (Hazmi and Wagner 2010a). Rubrarcastes has the similarly enlarged antennomeres of Arcastes, but the ratio of antennomeres 2 and 3 is 0.43-0.57 (Hazmi and Wagner 2010b). In the Oriental region, the relatively large body and the transverse depression on the pronotum distinguish Paraneolepta; antennomeres 4-6 are significantly widened in Orthoneolepta, which is different from that of Monolepta. In Ochralea Clark, 1865 the relatively large body (7.75-14.40 mm) and the deeply incised median lobe of aedeagus are characteristic (Hazmi and Wagner 2010c). The ratio of antennomeres of Neolepta is 0.75-0.80, Paraneolepta is 0.75-0.86, and Orthoneolepta 0.60-1.00. Neolepta is usually with widened median antennomeres. However, these three similar genera have a tansverse depression on pronotum, which is not present in Monolepta.
Eleven similar genera are distributed in China. In Atrachya Dejean, 1837, antennomere 3 is much longer than 2, and the tectum is deeply incised and with strong apical hooks (Lee 2020). In Sermyloides Jacoby, 1884, there is a strong frontal depression in males and a usually modified antennomere 3. In Ochralea Clark, 1865 antennomeres 2 and 3 are almost equal in length. In Shaira Maulik, 1936, the elytra is very short, and so this genus can be easily distinguished. In Pseudosepharia Laboissière, 1936, the epipleuron is very broad and 1/3 times as wide as the elytron. In Paleosepharia Laboissière, 1936, the epipleuron is gradually narrowed from its base to its apex, and there is sexual dimorphism (Lee 2018). In Macrima Baly, 1878, there is a frontal depression in males. Trichosepharia Laboissière, 1936 has the basal part of the median lobe incised and the tectum enlarged at its apex. In Chinochya Lee, 2020, tasomere 1 is swollen in males, and there are two types of endophallic spiculae. Tsouchya Lee, 2020, has antennomere 2 much shorter than 3, and there are two types of endophallic spiculae. In Neochya Lee, 2020 antonnomeres 2 and 3 are almost the same length, but the coxal cavities are widely open and there is only one pair of endophallic spiculae.
The species included in Monolepta generally have two types of antennae: either with segments 2 and 3 equal in length or with segment 3 longer than 2. Most species of the former group have a similar type of aedeagus; these include: M. babai Kimoto, 1996;M. bicavipennis Chen, 1942;M. kwangtunga Gressitt & Kimoto, 1963;M. mordelloides Chen, 1942;M. parvezi Aslam, 1968, andM. subflavipennis Kimoto, 1989. Since the redescription of the type species by Wagner (2007), "true" Monolepta can be distinguished by the similar lengths of antennomeres 2 and 3, the abruptly narrowed epipleuron after the basal 1/3, and the aedeagus type. Although, the closed anterior coxal cavities of Monolepta were the main character to identify the genus in the past, Wagner (1999Wagner ( , 2007 redescribed anterior coxal cavities of the type species and showed them to be open. So, these structures are rather variable, with some closed or almost closed and others completely open.
Although 73 species of Monolepta are known from China, little recent detailed work on the genus has so far been published, and some species with the second and third antennomeres of unequal length and different types of aedeagus may need to be transferred to other genera in the future, for example M. yaosanica Chen, 1942 and M. postfasciata Gressitt & Kimoto, 1963. The following key is restricted to those 68 species which have antennomeres 2 and 3 of equal length.

Key to the species of Chinese Monolepta
Note: the key only includes species with the second and the third antennomeres approximately equal in length (see generic Remarks). Elytra with a small spot near base, a slightly larger spot after middle (Suppl. material 1: Fig. S23, S24)  Antennae as long as body (Fig. 15)  Description. Length: 5.5-6.6 mm, width 2.7-3.7 mm. Holotype: length 6.6 mm, width 3.4 mm.
Head, pronotum, prothorax, scutellum, ventral side of mesothorax and metathorax, abdomen, and legs orange; clypeus and mouthparts black; antennae black except 1 st segment paler; tibiae slightly dark orange, tarsi black; basal area of elytra orange, middle to apical area black with an oval white spot.
Vertex slightly convex, with transverse wrinkles, punctures obvious, space between punctures almost equal to diameter of punctures, each puncture with a seta; frontal tubercle obvious, not deeply divided by ecdysial suture, triangular, glabrous and with several large punctures near frontal area; antennae longer than half of body, 1 st segment arc-shaped, length ratio of 2 nd and 3 rd segment 19: 18; length ratio of 4 th and the combination of 2 nd and 3 rd 2: 1.
Pronotum transverse, pronotum around 1.6 times as broad as long; disc slightly convex, glabrous, shallowly depressed on each side, surface with irregular strong and fine punctures, each puncture with short seta.
Scutellum triangular, smooth and impunctate. Elytra about 1.5 times as long as broad, basal part wider than pronotum; humeral angle obvious; two types of punctures in elytra: space between large punctures about 3 times as wide as diameter of puncture, small punctures irregularly distributed; epipleuron strongly narrowed after basal 1/3 and disappearing at the beginning of apex. Male. Last ventrite of male with trilobite concavities. The median apical lobe of the last sternite around twice as broad as long (Fig. 5). Aedeagus very slender, almost parallel-sided from base to middle, suddenly narrowed before 1/2 part, rounded at apex, slightly curved towards ventral side (Fig. 9). Tectum extends almost to apex of aedeagus (Fig. 8).
Female. Last ventrite of female with very slight concavities. Spermathecal cornu slender, curved almost vertical, middle part short, curved, nodulus middle narrow. Ventral part of bursa sclerites slender, slightly undulate at outer side, dorsal pair slender, pointed at apex.
Etymology. The specific epithet albipunctatus, -a, -um (meaning 'white-spotted') is a New Latin adjective formed from the Latin adjective albus, -a, -um ('white') and the New Latin adjective punctatus, -a, -um ('punctate', 'marked by spots or punctures'); it refers to the large white spots on the elytra of this species.
Distribution. China: Guangxi. Diagnosis. This species is similar to M. postfasciata Gressitt & Kimoto, 1963, but the latter has a smaller body with an obvious T-shaped black spot on each elytron, whereas M. albipunctata sp. nov. has a larger body with two separate large, white, round spots on each elytron. Description. Length: 2.5-3.5 mm, width: 1.5-2.0 mm. Holotype: length 3.5 mm, width 2.0 mm.

Monolepta alticola
Vertex orange, frons yellow, mouthparts dark brown; antennae dark brown except segments 1-3 brown; dorsal and ventral side of prothorax, coxae of front legs, femora yellow; scutellum, elytra, ventral side of mesothorax, metathorax, middle and hind legs dark brown; tibiae and tarsi of front legs pale brown, apex of middle and hind legs pale yellow.
Vertex convex, punctures sparsely and irregularly distributed; frontal tubercle developed; antennae longer than half of body, 1 st segment arc-shaped, length ratio of 2 nd and 3 rd segment 16: 15, length ratio of 4 th segment and the combination of 2 nd and 3 rd 45: 31.
Pronotum transverse, around 1.6 times as broad as long; disc slightly convex, shallowly depressed on each side, punctures unapparent, sparsely distributed; space between punctures wider than diameter of punctures.
Ventral surface of mesothorax, metathorax, and abdomen covered with long hairs. Width and length ratio of median apical lobe 1.1 (apex part width to length), 2.2 (basal part width to length) (Fig. 15). 1 st segment of hind tarsi about 1.7 times as long as remaining segments combined.
Etymology. The specific epithet alticola, altus (meaning 'living in high altitude') is a Latin adjective and the Latin col, ('lives'); it refers to the high-altitude habitat of this species.
Distribution. China: Yunnan. Diagnosis. This species is similar to M. schereri Gressitt &Kimoto, 1963 andM. epistomalis Laboissière, 1935. The main differences are the following: the ventral side of the meso-and meta-thorax and the abdomen of M. schereri are yellowish brown, whereas these are dark brown in M. alticola sp. nov. M. epistomalis has a dark-brown head and a yellowish-brown abdomen, whereas M. alticola sp. nov. has a yellow head and a black abdomen, and with the aedeagus tapering towards its apex. Description. Length: 3.0-3.6 mm, width: 1.5-1.7 mm. Holotype: length 3.6 mm, width 1.7 mm.

Monolepta bivittata
Head, dorsal and ventral side of prothorax, and legs yellowish brown; mouthparts, scutellum, ventral side of mesothorax and metathorax black; antennae black, except segments 1-3 yellowish brown; elytra and abdomen pale yellow, basal and postmedian area of elytra with transverse black stripe.
Vertex convex, with sparsely distributed punctures; frontal tubercle developed, trapezoid, glabrous and without punctures; antennae reach half of body, 1 st segment arc-shaped, length ratio of segment 2 nd and 3 rd 15: 16, length ratio of 4 th and combination of 2 nd and 3 rd 34: 31. Pronotum about 1.5 times as broad as long; disc slightly convex, shallowly depressed on each side, punctures unapparent and sparsely distributed.
Scutellum triangular, smooth and impunctate. Elytron about 1.5 times as long as broad; basal part wider than pronotum, humeral angle obvious; punctures evenly distributed, space between punctures is about 2 times as diameter of puncture, each puncture with seta; epipleuron strongly narrowed after basal 1/3, disappearring at beginning of apex. Ventral side of mesothorax, metathorax and abdomen covered with long hairs.
Male. Last ventrite of male with trilobite concavities. Width and length ratio of median apical lobe 1.4 (apex width to length), 1.5 (basal width to length) (Fig. 24). Aedeagus: ratio of length to width around 4:3; gradually and slightly tapering from base to near apex then abruptly constricted in distal 1/5 in lateral view; apex rounded and slightly pointed (Figs 25,27). Tectum broad, long, reaching to apex of aedeagus (Fig. 25).
Etymology. The specific epithet bivittatus, -a, -um (meaning 'bivittate', 'having two bands or stripes or vittae') is a New Latin adjective formed from the Latin prefix bi-(a shortened form of bis, 'twice') and the Latin adjective vittatus, -a, -um ('banded'); it refers to the two transverse black stripes on the elytra of this species, a character which distinguishes this species from all other species in the genus.
Distribution. China: Zhejiang. Diagnosis. This species is similar to M. leechi Jacoby, 1890, M. maana Gressitt & Kimoto, 1963, and M. liui Gressitt & Kimoto, 1963. The main differences are the following: the abdomen of M. leechi is black and the apex of the aedeagus is sharp, whereas the abdomen of M. bivittata sp. nov. is pale yellow and the apex of the aedeagus is blunt. The space between the punctures on the elytra of M. maana is equal to the diameter of the punctures, whereas in M. bivittata sp. nov., it is about twice the diameter of the punctures. The mid-and hind-legs of M. liui are dark brown, whereas the legs of M. bivittata sp. nov. are yellowish brown. Description. Length: 5.5-6.5 mm, width 3-3.5 mm. Holotype: length 6.5 mm, width 3.5 mm.

Monolepta mengsongensis
Head, dorsal and ventral side of prothorax, mesothorax, metathorax, and femora orange; mouthparts darker; antennae dark brown, 1 st segment pale; scutellum, tibiae, and tarsi black; a wide, transverse, pale, yellowish-brown stripe after middle part of elytra, which reaches middle sutures but not to lateral margins. Vertex convex, with transverse wrinkle, punctures obvious and evenly distributed, space between punctures is about twice as diameter of punctures; frontal tubercle developed, deeply divided by ecdysial suture, not reaching compound eye, triangular, glabrous and with a few punctures; antennae reach apex of elytra, 1 st segment arc-shaped, 2 nd antennomere equal to 3 rd , 4 th segment longer than sum of 2 nd and 3 rd .
Pronotum about 1.5 times as broad as long; disc slightly convex, shallowly depressed on each side; punctures obvious, densely and irregularly distributed, space between punctures wider than diameter of punctures.
Scutellum triangular, smooth and impunctate. Elytron nearly 1.6 times as long as broad; basal part broader than pronotum, humeral angle obvious; punctures evenly distributed, space between punctures about 2-3 times diameter of punctures. Epipleura strongly narrowed after basal 1/3 and disappearing at beginning of apex. Ventral side of mesothorax, metathorax and abdomen covered with long hairs.
Male. Last ventrite of male with trilobite concavities. Width and length ratio of median apical lobe 0.76 (apex width to length), 1.3 (basal width to length) (Fig. 31). Aedeagus almost straight, parallel sided in apical 1/5, slightly widened in the middle part, narrowed after 1/3 of apex, rounded at apex, slightly curved towards ventral side (Fig. 33). Tectum not reaching apex of aedeagus, apex rounded (Fig. 32). 1 st segment of hind tarsi about 1.5 times as long as remaining segments combined.
Head, pronotum, prothorax, and legs black; scutellum, elytra, mesothorax, metathorax, and abdomen orange to reddish brown. Basal 1/2 of hind femur orange. V e rtex slightly convex with transverse wrinkle v is ible o nl y laterally, punctures sp ar sely and irregularly dist ri buted; frontal tubercle developed, deeply divided by ecdydial suture, triangular, not very glabrous and with many wrinkles on; antennae reach half of the body, 1st segment arc-shaped, length ratio of segment 2nd and 3rd 19:21, length ratio of 4th and the combination of 2nd and 3 rd 23:18.
The pronotum is about 1.7 times as broad as long; disc slightly convex, shallowly depressed on each side; surface with irregular strong punctures, densely distributed near anterior margin, sparsely near basal margin. Anterior coxal cavities open.
Scutellum triangular, smooth and impunctate. Elytra is about 1.4 times as long as broad; basal part wider than pronotum, humeral angle obvious; punctures on elytra evenly distributed, with very short seta, space between punctures about 2-4 times as diameter of punctures; epipleuron strongly narrowed after basal 1/3 and disappearing at the beginning of apex. Ventral side of mesothorax, metathorax and abdomen glabrous, covered with longhairs.
The width and length ratio of median apical lobe is 1.2 (apex width to length), 2.3 (basal width to length) (Fig. 39). The 1 st segment of hind tarsi is about 1.5 times as long as remainder combined.
Male. Last ventrite of male with trilobite concavities. Aedeagus very slender and evenly narrowing from base to apex, apex rounded with a small cuspidate process. Tectum not reaching the apex of aedeagus, acute angle apex and curved towards ventral side (Fig. 43).
Etymology. The specific epithet rubripennis, rubripenne (meaning 'having red feathers or wings') is a New Latin adjective formed from the Latin adjective ruber, rubra, -um ('red') and the Latin noun penna, -ae ('feather', 'wing'); it refers to the red elytra of this species.
Distribution. China: Hunan, Fujian, Sichuan. Diagnosis. This species is similar to M. rufipennis Jacoby, 1899 and M. langbianica Kimoto, 1989. The main differences are the following: M. rubripennis sp. nov. has. an orange abdomen and black antennae, whereas M. rufipennis has a black abdomen and yellow antennae, and M. langbianica has yellowish-brown antennae and a yellowishbrown abdomen.