Two new genera and species of the Gigantometopini (Hemiptera, Heteroptera, Miridae, Isometopinae) from Borneo with remarks on the distribution of the tribe

Abstract Two new genera, each represented by a single new species, Planicapitus luteus Taszakowski, Kim & Herczek, gen. et sp. nov. and Bruneimetopus simulans Taszakowski, Kim & Herczek, gen. et sp. nov., are described from Borneo. Detailed photographs of male habitus and genital structures are presented. The checklist with distributional records for all known taxa of Gigantometopini is also provided.


Introduction
The Isometopinae are a highly autapomorphic group possessing paired ocelli which are absent in all other members of the plant bug family Miridae (Herczek 1993, Namyatova and Cassis 2016, Yasunaga et al. 2017. This subfamily was considered as the sister group to all other subfamilies based on morphology (Schuh 1974(Schuh , 1976, but recent works using molecular data do not support this hypothesis (Schuh et al. 2009, Jung andLee 2012). Therefore, additional works are needed to understand phylogenetic position of this subfamily.
The last tribe is Gigantometopini created by Herczek (1993) to accommodate a single species Gigantometopus rossi Schwartz & Schuh, 1990. In 2002 Isometopidea gryllocephala Miyamoto, Yasunaga & Hayashi, 1996 was transferred to a newly created genus Astroscopometopus Yasunaga & Hayashi and its inclusion to the tribe Gigantometopini was suggested (Yasunaga and Hayashi 2002). In 2004 another species of Isometopidea was described, Isometopidea formosana Lin, and the next year it was transferred to the genus Astroscopometopus (Lin 2005 Akingbohungbe, 2012. Yasunaga et al. (2017 transferred Isometopidea yangi (Lin 2005) to the genus Kohnometopus, suggested that this genus seemed better placed in Gigantometopini rather than in Myiommini, and also proposed to place the genus Isometopidea Poppius, 1913 (with the single species Isometopidea lieweni Poppius, 1913) in the tribe Gigantometopini. Moreover, it was found that the identity of the specimen of I. lieweni from Taiwan (Lin and Yang 2004) was based on a misidentification and it is a representative of an undescribed species. Subsequently Herczek et al. (2018) described one more genus and species within Gigantometopini, Sulawesimetopus henryi Herczek, Gorczyca & Taszakowski.
The most characteristic feature of Gigantometopini distinguishing it from other tribes is the large numbers of trichobothria (five or six on both mesofemur and metafemur) (Yasunaga et al. 2017).
In this paper, two new genera and species Planicapitus luteus gen. et sp. nov. and Bruneimetopus simulans gen. et sp. nov. are diagnosed and described; photographic images of habitus and genital structures, as well as scanning electron micrographs of the selected structures of both species are provided.

Materials and methods
The specimens were imaged by the following equipment: Leica M205C stereo microscope with high diffuse dome illumination Leica LED5000 HDI, Leica DFC495 digital camera and Leica application suite 4.9.0 software; Leica DM 3000 upright light microscope with Leica MC 190 HD digital camera and Leica Application Suite 4.12.0 software. SEM photographs were obtained using Phenom XL field emission scanning electron microscope at 5 and 10 kV accelerating voltage with a BackScatter Detector (BSD). Graphic editor Adobe Photoshop CS6 was used to prepare the figures. In case of legs, the preparations for SEM were made with methods traditionally used in morphological studies (e.g. Kanturski et al. 2015, Herczek et al. 2018. In contrast, during preparation of other photographs, steps that can damage the specimen e.g., washing, dehydration and sputter-coating with a film of electrically conducting material, have not been applied. Specimens on original glue boards were only cleaned with a brush and mounted on aluminium stubs with double-sided adhesive carbon tape. Next, the specimens were covered with anti-static spray. Map was prepared in SAGA GIS 7.1.1 (http://www.saga-gis.org) using WGS84 datum and EPSG: 3395 (World Mercator cylindrical projection).
Measurements were made with Leica application suite 4.9.0 software and are presented in millimetres (mm). Terminology of morphological structures mainly follows Herczek et al. (2018) and Kim and Jung (2019). Dissections of male genitalia were performed using Kerzhner and Konstantinov's (1999) technique. The terminology for genital structures follows Konstantinov (2003). The study was based on material deposited in the collection of the Royal Belgian Institute of Natural Sciences (RBINS) and material recently collected by Claas Damken during an extensive survey of the Heteroptera fauna of Brunei Darussalam, deposited at Universiti Brunei Darussalam Museum, Brunei Darussalam (UBDM). From 2013 to 2015, sampling took place at different locations and forest types across the Bornean Sultanate using a range of methods (e.g., generator-powered light traps, sweep netting, collecting by hand, litter sifting, pitfall traps, Malaise traps, examination of bycatch from other studies). During this field survey, more than 400 species of Heteroptera were collected, including several species of Isometopinae (https://tinyurl.com/ Brunei-Isometopinae).
Description. Male. Body oval, slightly elongated ( Fig. 1A). Head clearly higher than wide, dorsally extending to highest point of pronotum, flattened, impunctate but wrinkled; Antenna thin (particularly segments III and IV). Labium reaching third abdominal segment (Fig. 1B). Pronotal collar with row of punctures. Pronotum distinctly punctuate, distinctly carinate at sides, with slightly upturned lateral margins; calli slightly marked, separated by shallow fossa. Scutellum convex, wider than long, basomedially clearly depressed. Thoracic pleura distinctly punctate (Fig. 1C). Ostiolar peritreme small, strongly convex and covered with fine spines ( Remarks. Affiliation of Planicapitus luteus to the Gigantometopini is clearly confirmed by the following features: compound eyes relatively small, significantly separated from each other, pronotum deeply punctate and elongate, calli separated by shallow fossa, pronotal collar demarcated by row of punctures, inflated scutellum, and five mesofemoral trichobothria (Herczek 1993, Yasunaga et al. 2017. Set of features mentioned in the diagnosis clearly differ the new genus from other genera belonging to Gigantometopini. Planicapitus luteus belongs to the smallest representatives of tribe. The new genus is similar in size to Isometopidea lieweni which body length of the only known specimen equals to 3.0 mm. It is a female, so probably (like other representatives of tribe) males reach a smaller body size (Poppius 1913, Yasunaga 2005, Herczek et al. 2018. Isometopidea further differs from newly described genus by the structure of the head, which is not higher than wide, somewhat rounded and not strongly flattened in front. Sulawesimetopus, the second comparatively smallsized genus of the Gigantometopini, is slightly larger and can be distinguished from the new genus by the three segmented tarsi and punctured head. Other representatives of Gigantometopini are a way larger than the new genus in body size.  Description. Male. Body shiny, yellow-brownish, covered by semi-erect palebrown seta (Fig. 1A-C). Head: yellow-whitish, 1.5 times as high as wide, compound eyes reddish yellow, vertex orange, convex, 1.3 times as wide as eye width in dorsal view. Frons whitish, with two small dark brown spots ventrally extending into large Y-shaped brown macula; gena whitish yellow (Figs 1C, 2A, B). Antenna yellowish. Labium shiny, yellowish, segment IV with brown apex (Fig. 1B). Thorax: pronotum yellow, semi-transparent laterally; exposed part of mesoscutum yellow, scutellum yellowish brown, with apex white and lateral angles narrowly whitish, 0.7 as long as wide. Pleura yellowish brown, with red stripe from propleuron to episternum (Fig. 1B, C). Ostiolar peritreme ivory, evaporative area yellow (Fig. 1B, C). Claval commissure 0.6 times as long as scutellum. Hemelytron: in various shades of yellow, median part with two whitish spots. Cuneus 0.9 times as long as wide, yellowish, with white spot in basal inner corner. Membrane pale grey, semi-transparent, with two cells. Legs: coxae pale, almost white, femora yellow-white (Fig. 1B, C), with brown spots, tibiae yellow with dark brown spots, tarsi yellow (Fig. 1B, C). Abdomen: bicoloured, dark brown, except for pale yellow genital segment (Fig. 1B, C). Genitalia: as described above. Measurements: given in the   Diagnosis. Distinguished by vertical, slightly flattened head, not punctured but wrinkled and higher than wide, dorsally not extending to level of highest point of pronotum; vertex slightly convex, protruding above eye level, width of vertex equal to eye width; dorsum and pleurites of thorax with deep and dense punctures; calli slightly marked, tarsi two segmented, claw with very small, barely noticeable apical tooth; labium reaching third abdominal segment, right paramere well developed, with kneeshaped sensory lobe; left paramere ca. 1.5 times as long as right one.
Remarks. Affiliation of Bruneimetopus to the Gigantometopini is clearly confirmed by the same set of features as for Planicapitus (see above). It is also indicated by presence of six metafemoral trichobothria (the specimen of Planicapitus luteus is devoid of hindlegs).
As in the case of Planicapitus, set of features mentioned in the diagnosis clearly differ the new genus from other genera belonging to Gigantometopini. The newly described genera are very similar morphologically to each other. However, in addition to small differences in the proportions of body parts and coloration, they can easily be distinguished by the completely different shape and size of the right paramere. This was a premise to describe them in separate genera.
Etymology. Name combines Brunei (the type locality) with part of the generic name Isometopus, the type genus of the subfamily.
Description. Male. Body shiny, in various shades of yellow and brown, covered by semi-erect pale brown and brown setae (Fig. 6A-C). Head: brownish yellow, 1.4 times as high as wide, compound eyes reddish, vertex white, slightly convex, as wide as eye in dorsal view. Frons dark brown between eyes, yellowish below inferior margin of eyes; clypeus brown; gena yellow ( Fig. 7A-C). Antenna yellowish, segments III and IV  darker. Labium shiny, yellowish, segment IV brown (Fig. 6B). Thorax: pronotum dark yellow, lateral margins semi-transparent and slightly raised, slightly wider at front; posterior margin whitish. Exposed part of mesoscutum brown with yellow tinge. Scutel-lum dark brown, with white apical part and black extreme apex, 0.6 times as long as wide, covered by semi-erect setae. Propleuron dark yellow, meso-and metapleurons dark brown with dark yellow tinge. Ostiolar peritreme ivory, evaporative area yellowbrown ( Fig. 4D-F). Claval commissure comparatively long, 0.5 times as long as scutellum. Hemelytron: in various yellow and brown shades: median, posterior part and cuneus in 2/3 of their length semi-transparent, whitish yellow, base of hemelytra and clavus yellow-brown, part neighbouring with cuneal fracture and 1/3 length of cuneus dark brown. Cuneus 0.9 as long as wide. Membrane pale grey, semi-transparent, with two cells. Legs: coxae yellowish pale, femora yellow-white, with brown spots apically, tibiae yellow with four or five dark brown, irregular rings, tarsi yellow (Fig. 6A, B). Abdomen: bicolored: first two segments yellowish to brown, others dark brown (Fig.  6B, C). Genitalia: as described above. Measurements: given in the Table 1.   Etymology. The species name simulans (resembling) is the present participle of the Latin verb simulo (to make like or to assume the appearance of anything), in allusion to the resemblance of this species to Planicapitus luteus.
Biology. Unknown. Two specimens were collected in a mangrove forest (