﻿Platyintybia, a new genus of Apalochrini (Coleoptera, Melyridae, Malachiinae) from China

﻿Abstract A new genus of malachiine Melyridae, Platyintybiagen. nov., is described based on several male-specific characters, along with description of its type species, Platyintybiazhongshanensissp. nov., from China. A new combination, Platyintybiasarawakensis (Champion, 1921), comb. nov., is proposed after examining the type specimen; this species is newly recorded from China. A key to the genera of Chinese Apalochrini is provided for the first time.


Introduction
Apalochrini is one of the monophyletic tribes of malachiine Melyridae, characterized by a shortened pedicel, which is almost concealed in the scape.This tribe comprises more than 40 genera from all over the world, with new genera still being described in the past few years (Evers 1987;Tshernyshev 2015aTshernyshev , 2015bTshernyshev , 2016aTshernyshev , 2020aTshernyshev , 2020bTshernyshev , 2020cTshernyshev , 2021aTshernyshev , 2021bTshernyshev , 2021c;;Liu et al. 2020Liu et al. , 2021;;Tshernyshev and Shcherbakov 2020).The genera of Apalochrini are distinguished by different combinations of characters of the antenna, head, pronotum, elytra, legs, etc., in males (Evers 1987;Tshernyshev 2015b).Members of this tribe mostly inhabit areas close to water bodies, like streams, lakes, salt lakes, and even oceans (Liu et al. 2021).Larvae and adults of Apalochrini are predators or scavengers, feeding on smaller or dead creatures, and sometimes can be collected on flowers (Horne et al. 2000;Liu et al. 2021;Zhenhua Liu pers. obs.).

Materials and methods
Materials examined in this study are deposited in the following institutions: IZGAS Institute of Zoology, Guangdong Academy of Sciences, Guangzhou, China FAF Fujian Academy of Forestry, Fuzhou, China BMNH The Natural History Museum, London, United Kingdom Specimens for dissections were cleared in 5% solution of KOH for about 12 h at room temperature.The abdomen with the aedeagus was transferred to a cavity slide, and the aedeagus was separated from the abdomen using a hooked, fine dissecting needle.Specimens are mounted on Goodrech cards using white emulsion glue, and the genitalia and terminal abdominal segments are preserved in genitalia vials with glycerol.
Layered images of specimens and male genitalia were captured using the Canon 7D DSLR camera mounted on a Wemacro Focus Stacking Rail, with Canon MPE-65 mm macro lens, Mitutoyo 5× and 10× objective lens, and dual-headed flash, with the aid of Helicon Remote (v.3.9.10M) and WeMacro Control software.The images were stacked in Helicon Focus v. 8.1.1 software and edited in Photoshop CC 2022.
The morphological terms used in this paper follow Lawrence and Ślipiński (2013).The following standard measurements are used in this study: body length-from apical edge of clypeus to apex of abdomen; pronotal length-median line from anterior margin to posterior margin; pronotal width-maximum width of pronotum; elytral length-from base of scutellum to elytral apex along suture; elytral width-maximum width across the elytra.
Etymology.The genus name is a combination of the Latin word platys and the genus name Intybia; platys means broad, referring to the modified terminal antennomere in male.Gender feminine.
Diagnosis.This genus can be recognized from other genera of Apalochrini by combination of the following male specific characters: antenna with scape and antennomere 3 dilated and modified, antennomere 11 enlarged and flattened; head with pair of concavities on head between eyes; front tarsi 4-segmented, without comb on tarsomere 2. It can also be separated from Collops Erichson, 1840 and some species of Notointybia Liu, Ślipiński & Pang, 2020, which also with 4-segmented front tarsi, by having lateral margins of the pronotum without a bead.
Male.Head and pronotum black, elytra black with pair of large white spots at about basal fourth and pair of smaller white spots at about anterior fourth; antenna yellow with base of scape and terminal segment black; ventral surface mostly black, abdomen orange with lateral areas more or less black.Vestiture comprising double row of dense, short, whitish setae and sparser, longer, black bristles.
Pronotum longer than wide, widest at about middle; lateral margins slightly curved, moderately constricted at base, without lateral carina; posterior margin nearly truncate.Disc finely, densely punctate, smoother at middle, posterior area with shallow transverse depression, covered with dense, depressed setae.Prosternum short, with deep incision anteriorly between pronotum and prosternum.Procoxal cavities transverse, continuous at middle, externally open.Procoxae projecting, with protrochantins exposed.Scutellum with visible part subtrapezoidal, posterior margin almost truncate.
Abdomen with 6-segmented ventrites, freely articulated, gradually narrowed to posterior.Tergite VIII transverse, subtrapezoidal, with pair of anterior struts; sternite VIII nearly divided, weakly connected by membrane at middle (Fig. 4).Aedeagus slender and curved, with apex upwardly curved; endophallus with 1 slender sclerite and a few short sclerites around it.
Female.Similar to male in body shape and colouration, but antenna with basal and apical segments simple, head without concavity on vertex, and front tarsi 5-segmented.
Distribution.China (Fujian, Guangdong); Malaysia (Borneo).Diagnosis.The new species resembles Platyintybia sarawakensis in the shape of the basal antennomeres and aedeagus, but it can be easily recognized from the latter by the transverse basal spot and a much smaller subapical spot on the elytra (Fig. 1A).It also differs from P. sarawakensis in the following characters in males: apical antennomere more rounded (Fig. 3C); front tibiae distinctly slender (Fig. 3D); tergite VIII with posterior margin less emarginate (Fig. 4C); penis less curved laterally (Fig. 4A, F), apex of penis more depressed ventrally (Fig. 4B, G), the shape of long sclerite in inner sac (Fig. 4B, G).

Platyintybia zhongshanensis
Description.Length 2.7 mm. Male.Antenna mostly yellow, with base and inner edge of scape and apical antennomere black.Legs with middle and hind legs black; front leg with basal half of femora and base of tibiae black, apex of tibiae and apical tarsomere dark brown, remaining parts yellow.Elytra with basal spots whitish and transverse, not extending to lateral or inner suture; subapical spots much smaller, more or less yellowish.Abdominal ventrites mostly orange-red, with lateral areas black.
Head about 1.1 times as wide as pronotum; concavities on head almost extending to anterior margin of eyes; width of vertex between concavities about 1.1 times as wide as concavity across middle of eyes.Dorsal surface of head with pair of circinately arranged setae behind antennal insertions and one on vertex between concavities.Antenna with scape elongate, subtriangular, and constricted at base; antennomere 3 elongate, with a large lamellate process at base, dorsal surface with 1 large, rounded anterior concavity and 2 much smaller basal concavities.
Pronotum about as long as wide.Elytra about 1.6 times as long as wide; epipleura extending to apical margin of elytra but not to apex.Front tibiae about 7.7 times as long as wide, front tarsi 4-segmented.
Abdomen with tergite VIII subtrapezoidal, posterior margin with wide, transverse emargination (Fig. 4C); sternite VIII divided.Male genitalia with penis slender, dorsoventrally curved, apex constricted and upwardly curved; inner sac with a slender and curved sclerite and a few small sclerites around it, apex with dense small denticles (Fig. 4A, B). Female.Unknown.

Distribution. China (Guangdong).
Biology.This species is collected with Intybia swatowensis (Wittmer, 1956) on grass beside a stream in a village, which is consistent with the habitat of most Apalochrini.Feeding habits and behaviour of this species are unknown.Male.Antenna mostly yellow with base of scape and apical antennomere black.Legs with femora mostly black, apex of front and middle tibiae rufous; front tibiae and tarsi rufous, middle tibiae brownish to black, hind tibiae black with basal part rufous, middle and hind tibiae brownish.Elytra with basal spots large and suboval, not extending to lateral or inner suture; subapical spots rounded, a little smaller.Abdominal ventrites mostly orange-red, with lateral areas black.
Head about 1.1 times as wide as pronotum; concavities on head not extending to anterior margin of eyes; width of vertex between concavities about 1.5 times as wide as concavity across middle of eyes.Dorsal surface of head with pair of circinately arranged setae behind antennal insertions.Antenna with scape elongate, subtriangular, and constricted at base; antennomere 3 elongate, with large lamellate process at base, dorsal surface with 1 large, transversely elliptical anterior concavity and 2 indistinct basal concavities.
Pronotum about as long as wide.Elytra about 1.5 times as long as wide; epipleura not extending to apical margin of elytra.Front tibiae about 6.4 times as long as wide, front tarsi 4-segmented.
Female.Resembling male in colour and body shape, but with antennae more brownish, scape and antennomere 3 only slightly dilated, terminal antennomere simple; head without concavity on vertex; front tarsi 5-segmented.
Distribution.China (Fujian), Malaysia (Borneo).Biology.Information on feeding habits and behaviour is scarcely known.The Chinese specimens were found on the leaves of plants in a mangrove forest, and the holotype was collected on Mount Matang without details of the habitat noted.

Discussion
Platyintybia sarawakensis was assigned to the Intybia rouyeri group mainly on account of its colour pattern of black with two whitish or yellowish spots on each elytron (Plonski 2016).The male-specific characters on the vertex, apical antennomeres, and front tarsi were not mentioned by Champion (1921) when describing this species.More species might be transferred to Platyintybia after the holotypes are examined.In Apalochrini, the 4-segmented front tarsi in males have been found in Collops, Notointybia, and Platyintybia, which are distributed in different biogeographic areas (Liu et al. 2020), meaning that this character must have evolved independently in those genera rather than being an autapomorphy.However, relationships between these genera and related genera require further study.
Although Dromanthomorphus is included in the key, the only species found in China, Dromanthomorphus mirabilis (Pic, 1907) actually lacks some apomorphies, such as excavate front and middle tibiae, swollen metathoracic mesepimera, and possession of an appendage directed forward to the middle coxae (Tshernyshev 2016b;Liu et al. 2023).No nomenclatural act on this species is proposed here, as Isidor Plonski (pers.comm) is working on this species.In the above key, Dromanthomorphus specifically refers to D. mirabilis only.

Figure 1 .
Figure 1.Habitus of Platyintybia zhongshanensis Liu & Wang, sp.nov.A dorsal view, male B ventral view, male C lateral view, male D habitus photograph.Scale bars: 1 mm for A-C.

Figure 3 .
Figure 3. A-E Platyintybia zhongshanensis Liu et Wang, sp.nov.F-J Platyintybia sarawakensis(Champion, 1921) A, G antenna, male B, H lateral view of basal antennomeres, male C, I dorsal view of antennomere 11, male D, F fore tibia, male E, J dorsal view of head, male.