Monolepta Chevrolat, 1837

Lei, Qi-long, Xu, Si-yuan, Yang, Xing-ke & Nie, Rui-E, 2021, Five new species of the leaf-beetle genus Monolepta Chevrolat (Coleoptera, Chrysomelidae, Galerucinae) from China, ZooKeys 1056, pp. 35-57 : 35

Genus Monolepta Chevrolat

Monolepta Chevrolat 1836: 383. Type species: Crioceris bioculata Fabricius, 1781, by subsequent designation ( Chevrolat 1845: 5).

Damais Jacoby 1903: 118. Type species: Damais humeralis Jacoby, 1903, by monotypy. Synonymized by Maulik (1936: 373).

Aemulaphthona Scherer 1969: 89. Type species: Aemulaphthona ochracea (Weise, 1922), by monotypy. Synonymized by Konstantinov (2002: 210).

Chimporia Laboissière 1931: 413. Type species: Chimporia monardi Laboissière, 1931, by monotypy. Synonymized by Wagner (2007: 84).

Distribution.

Palaearctic, Oriental, Australian, Afrotropical, Neotropical region.

Diagnosis.

Body length: 1.9-9.5 mm. Antennae longer than half or even equal to the body, segments 2 and 3 almost equal in length, segment 4 equal to or longer than sum of segments 2 and 3. Width of pronotum longer than length; anterior margin slightly depressed, basal margin protruding and lateral margins slightly protruding; basal margin and lateral margins with frame; anterior and posterior angle thickened, each angle with a seta-pore; disc convex, generally depressed on both sides. Scutellum triangular, smooth, and impunctate. Elytra broader than pronotum, humeral angle obvious; epipleuron broad before basal 1/3, then strongly narrowed and disappearing at beginning of apex. Anterior coxal cavities open or closed, each tibia with a spine in apex, spine of hind tibiae longest, 1st segment of hind tarsi longer than remaining segments combined; claws appendiculate. Last sternite of male with trilobate concavities, female normal, without any concavities ( Gressitt and Kimoto 1963).

Remarks.

Since its description, several genera have been synonymized with Monolepta . Of these, Maulik (1936) synonymized Damais Jacoby, 1903 based on the length 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, and M. 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 (1999, 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.