A revision of the genus Hemitrochostoma (Hemiptera, Heteroptera, Plataspidae)

Abstract The genus Hemitrochostoma Bergroth, 1913 (Hemiptera, Heteroptera, Plataspidae) is redescribed and reviewed. Two species are recognized: the type species Hemitrochostoma altilabris Bergroth, 1913 (Malaysia: Sarawak), and Hemitrochostoma rutabulum sp. n. (Malaysia: Perak). The following new subjective synonymies are proposed: Hemitrochostoma Bergroth, 1913 = Inflatilabrum Tomokuni, 2012, syn. n.; Hemitrochostoma altilabris Bergroth, 1913 = Inflatilabrum lambirense Tomokuni, 2012, syn. n.


Introduction
The genus Hemitrochostoma Bergroth, 1913 (Hemiptera, Heteroptera, Plataspidae) has remained monotypic so far; the single included species, H. altilabris Bergroth, 1913 was described from Borneo, Malaysia. Except for a paper briefly discussing the peculiar morphology of H. altilabris (Rédei & Bu, 2013) we could not trace any literature mentioning the genus or species. Hemitrochostoma and its included species are redescribed, an additional new species is described, and new genus and species-level synonymies are proposed in the present paper.

Material and methods
External structures were examined using a stereoscopic microscope (Zeiss Discovery. V8). Drawings were made with the aid of a camera lucida. Genitalia were dissected after careful maceration in KOH, stained with Chlorazol Black E if necessary, and examined using stereoscopic (Zeiss Discovery V8) and optical (Olympus CX21) microscopes. Digital photographs were taken with a Nikon D90 camera equipped with an AF-S Micro Nikkor 60mm f/2.8G ED lens.
Measurements were taken with calibrated micrometer eyepiece. Since the apical portion of the mandibular plates are strongly curved upwards, the length of the head was measured to the apex of the anteclypeus in dorsal position of the frontoclypeus, and to the apex of the mandibular plates in the most exposed (anterodorsal) position of the head.
The two species of this genus are highly similar in their colour, integument, vestiture, and external morphology. Therefore in order to avoid repetitions a rather detailed description of the genus is provided; the species descriptions are kept short and focus on the diagnostic characters of the two species. Morphological terminology mostly follows Tsai et al. (2011).
Abbreviations for depositories: HNHM, Hungarian Natural History Museum, Budapest, Hungary; NSMT, National Museum of Nature and Science (formerly National Science Museum), Tokyo, Japan; ZJCP, Zdeněk Jindra's private collection, currently deposited at the Department of Plant Protection, Czech University of Agriculture, Prague, Czech Republic.
Head and cephalic appendages. Head (Figs 5-8) 1.05-1.1 times as long as its width across eyes, about as long as or slightly longer than median length of pronotum, about half as broad across eyes as humeral width of pronotum, width across eyes 1.3-1.35 times (male, female) as broad as interocular distance; sexually dimorphic: males (Figs   Figures 1-4. Hemitrochostoma rutabulum sp. n., male 1-2 and female 3-4. 1, 3 dorsal view 2, 4 ventral view. Scale in mm. 5, 7) with more strongly broadened mandibular plates than females (Figs 6,8); anteclypeus thick, with lateral margins arched, therefore anteclypeus distinctly broader at its middle than apically and basally, dorsally elevated above level of mandibular plates (Fig. 11); mandibular plates broadly, laminately produced, far surpassing apex of clypeus, overlapping medially anteriad of clypeus but separated from apex of clypeus by a distinct gap, lateral margin of mandibular plates sharp, reflexed, distinctly (H. altilabris male, H. rutabulum male, female) or insignificantly (H. altilabris female) emarginate anteriad of eye, portion anteriad of apex of clypeus strongly turned upwards; antennal insertion situated closer to mesal margin of eye than to base of labium (Fig.  10); buccula short, restricted to basal half of ventral side of head; labrum subdivided into a broadly inflated proximal portion (Figs 10-11: lbrp) and a highly elevated, crestlike distal portion semicircular in lateral view (Figs 10-11: lbrd); compound eyes very small (male, female), distinctly protruding laterally; ocelli small, interocellar distance about 2 times as long as distance between ocellus and ipsilateral eye. Antenna simple, segment II subdivided into two secondary segments, segment I not reaching apex of head, thickened at its basal half, segment IIb very short, ring-like, segments IIb-IV distinctly flattened. Labium reaching or surpassing posterior margin of abdominal ventrite III; segment I (Figs 10-11: lb 1 ) thick and short, not reaching base of head, diameter of segments II-IV much smaller, segment III distinctly longer than segment I, segments II and IV subequal in length, both distinctly longer than segment I.
Thorax and thoracic appendages. Pronotum (Figs 5-8) more than two times as broad as its median length, moderately declivous anteriorly; anterior collar narrow but distinct; lateral margin broadly, laminately explanate, more or less strongly produced anterolaterad reaching or surpassing anterior margin of eye, gradually narrowed posteriad, more or less emarginated anteriad of humeri in dorsal view; humeral angle rounded, obtuse, distinct; posterior margin broadly rounded, posterolateral angle obsolete. Scutellum wider than long, lateral margins abruptly broadened at their extreme base, then moderately broadening posteriad, forming a broadly rounded angle at two thirds of its length, then more strongly narrowing towards apex; basal tumescence weak, posteriorly delimited by a broad and very shallow transversal furrow; disk with a very indistinct median carina; basolateral angle not delimited by furrow; with a fine submarginal impression along almost entire length except at extreme base; posterior margin shallowly (female) or more deeply (male) excised above terminalia. Thoracic pleura and sterna (Fig. 9). Proepisternum simple, not tumescent; metapleuron with a well developed scent gland ostiole situated about halfway between base of hind coxa and dorsal margin of metapleurite, associated with a distinct, well developed but rather short, highly elevated, elongate, weakly curved peritreme; mesosternum forming a broad, obtuse, rather low median carina, posterior margin V-shaped and distinctly produced between mid coxae; metasternum relatively narrow, elevated and somewhat tumescent, but meso-and metasterna not forming a contiguous carina. Evaporatorium occupying most of thoracic pleuron and sternum except broad lateral explanate margin of propleuron, adjacent broad region of proepisternum, and pro-and mesothoracic supracoxal lobes. Fore wing. Exocorium and adjacent small, triangular basal portion of mesocorium exposed in rest. Legs short, femora thickened, tibiae with distinct, broad, deep dorsal furrow along their whole length.
Pregenital abdomen (Figs 9, 26) distinctly broader than long; connexival segments distinctly separated, intersegmental sutures running to lateral margin of abdomen; Figures 5-8. Hemitrochostoma species, head and pronotum in most exposed view. 5 H. altilabris Bergroth, 1913, male 6 same, female 7 H. rutabulum sp. n., male 8 same, female. Pilosity only shown along margin of head and pronotum. Scale in mm. posterolateral angles of segments IV and V minutely, obtusely, protruding; dorsal laterotergites present in segments III-VI, rather broad; ventral laterotergites greatly fused with the respective sternites (these ventral plates of composite origin are termed ventrites), lateral portions of ventrites III-VII demarcated by a longitudinal furrow, spiracles III-VII situated close to this furrow mesally and about halfway between anterior and posterior margin of each segment; segments III-VII each with 2 pairs of longitudinally arranged trichobothria situated posteriad and somewhat mesad of the respective spiracles in an oval impression; median lengths of ventrites III-VI subequal, that of ventrite VII somewhat longer (female); posterior margin of ventrite VII of female deeply, subtriangularly emarginate (cf. Figs 26, 28, 32); tergite VIII ( Fig. 27: t 8 ) short, narrowly desclerotized along midline.
Postgenital abdomen. Male: proctiger elongate, concealing dorsal sinus of posterior aperture of genital capsule in rest, weekly trilobate apically (Figs 13, 15). Female: segment X transversally subdivided into two secondary segments (Fig. 29: t 10 -p, t 10 -d) and each of these secondary segments subdivided into a pair of contralateral sclerites along midline.
Distribution and diversity. The genus previously contained only the type species occurring in northern Borneo. Another species is described in the present paper from Peninsular Malaysia (Perak). Bergroth, 1913 Figs 5-6, 9-13, 16-21, 24-31 Hemitrochostoma altilabris Bergroth, 1913:  Diagnosis. Differs from the only known congener, H. rutabulum sp. n., by the less-dilated mandibular plates in both sexes and the less-produced anterior angles of the pronotum (not extending to anterior margin of eye in dorsal view) (Figs 5-6).

Hemitrochostoma altilabris
Redescription. Male and female. Photographs of the habitus and diagnostic characters of both sexes were presented by Tomokuni (2012) under the name Inflatilabrum lambirense.
Colour and integument. Dorsum of body brown, following parts ochraceous: mandibular plates except their narrow lateral margin, a middorsal vitta between base of clypeus and base of head usually narrowing towards base of head; explanate lateral margin, a pair of transverse submedian fasciae between collar and calli, some suffused spots at posterior margin of calli, and humeral tubercles on pronotum; a pair of distinct or indistinct spots at basal tumescence and occasionally an indistinct median vitta on disk of scutellum; visible portion of costal margin of fore wing; lateral and posterior margins of scutellum broadly marmorated with ochraceous of various extent; legs ochraceous, antennae slightly darker, brownish ochraceous; venter of head brown, ventrally visible surfaces of mandibular plates and clypeus ochraceous, labium ochraceous, ventrally visible portions of thorax and abdomen brown, explanate lateral margin of propleuron ochraceous, abdominal ventrites somewhat lighter brown than pterothoracic pleura, lateral margin and an adjoining  Lettering: aed = aedeagus, bp = basal plates, cp-I, cp-II 1 , cp-II 2 = conjunctival processes (see text), dej = ductus ejaculatorius, ds = ductus seminis, erp = erection fluid pump, res = endophallic reservoir, sbc = support bridge complex, sbp = support bridge prolongation. Scales in mm. sublateral spot at anterior margin of each of ventrites III-VII ochraceous. Integument and vestiture as in the generic description.
Structure. Head (Figs 5-6) with lateral margin of mandibular plates weakly (male) or insignificantly (female) emarginate anteriad of eye, then more or less straight, slightly diverging anteriad (male) or subparallel (female), apically abruptly truncate (male, female). Pronotum (Figs 5-6) with anterolateral angles distinctly produced anteriad but not reaching anterior margin of eye (male, female). Other characteristic of the exoskeleton as in generic description. A detailed description, habitus photos and photos of diagnostic characters of both sexes were provided by Tomokuni (2012) under the name Inflatilabrum lambirense.
External male genitalia. Genital capsule (Figs 12-13) with a pair of weak lateral notches in posterior view, therefore lateral margins appearing weakly emarginate in most exposed view; cuplike sclerite ( Fig. 12-13 Figs 18, 20); conjunctiva voluminous, greatly membranous, provided with a pair of dorsolateral membranous, partially sclerotized processes (probably homologous with cp-I of Tsai et al. 2011) (Figs 18-20: cp-I) and a pair of lateral processes which are broadly membranous proximally but terminating in 2 strongly sclerotized, long, spine-like projections distally (Figs 18-20: cp-II 1 and cp-II 2 ); endophallic reservoir (Figs 18-19: res) small, with a pair of ventral protuberances associated with distal parts of support bridge prolongation, separated by basal portion of aedeagus s. str. by a deep, narrow incision; aedeagus s. str. (Figs 18,20,25: aed) greatly elongate, narrow, tubular, strongly curved in an S-shape in the sagittal plane, narrowly enclosing the tubular endophallic duct (Fig. 24: end) in most of its length except in the area of a strongly elevated, carina-like dorsal lump immediately distad of its middle which encloses an inner chamber (Fig. 24: ich); apex of aedeagus s. str. obliquely truncate.
Immatures. Description and photograph of the 5 th -instar larva were presented by Tomokuni (2012) under the name Inflatilabrum lambirense.
Discussion. Hemitrochostoma altilabris was described based on an unspecified number of specimens (all males). The type depository was not indicated in the original description (Bergroth 1913). The type(s) could not be located in the Zoological Museum of the University of Helsinki (L. Huldén, pers. comm.) currently housing most of the types of E. Bergroth (Schuh and Slater 1995), and also was not found in other important depositories of Bergroth types: the Zoological Museum of the Humboldt University of Berlin (J. Deckert, pers. comm.), the Senckenberg Deutsches Entomologisches Institut in Müncheberg (S. Blank, pers. comm.), the HNHM, the Naturhistorisches Museum in Vienna, and the Natural History Museum in London (all of them visited by DR). Because the specimens examined by us were collected rather close to the type locality, and the males are in agreement with the description and illustrations of Bergroth (1913), they are readily identified as H. inflatilabrum. Although the type material currently cannot be located, so far there is no doubt about the identity of this species and, therefore, designation of a neotype is not justified.
Diagnosis. Easily distinguished from the only known congener, H. altilabris by the much more strongly dilated mandibular plates, particularly in the male (Fig. 7) but also in the female (Fig. 8), and the more produced anterior angles of the pronotum (surpassing anterior margins of eyes in both sexes) (Figs 7, 8). The ground colour of the two examined specimens is considerably darker than in H. altilabris, and the scutellum is not marmorated with ochraceous along its lateral and posterior margin.
planate lateral margin, a pair of transverse submedian fasciae between collar and calli, weak suffusion at posterior margin of calli and on humeral tubercles, and an indistinct median vitta on disk of pronotum; visible portion of costal margin of fore wing; a pair of distinct or indistinct spots at basal tumescence, and a narrow vitta along midline starting slightly posteriad of basal tumescence and fading away before posterior margin of scutellum; legs ochraceous, antennae slightly darker, brownish ochraceous; venter of head brown, ventrally visible surfaces of mandibular plates and clypeus ochraceous, labium ochraceous, thoracic pleura (except explanate lateral portion of propleuron) and abdomen dark brown, lateral margin and an adjoining sublateral spot at anterior margin of each of ventrites III-VII ochraceous. Integument and vestiture as in the generic description.
Structure mainly as in generic description. Head with lateral margin of mandibular plates distinctly emarginate anteriad of eye (male, female), then strongly broadened, anteriormost portion rounded. Pronotum with anterolateral angles strongly produced anteriad, distinctly surpassing anterior margin of eye in both sexes but more strongly in male.
External male genitalia. Genital capsule (Figs 14-15) broadly rounded laterally. Paramere as in Figs 22-23. Phallus generally similar to that of H. altilabris, it was not examined in detail.
Female terminalia (Fig. 32). Posterior margin of ventrite VIII more broadly emarginate than in H. altilabris, proximal margin of valvifer VIII rather rounded; laterotergite IX distinctly broader than that of H. altilabris. The single available female was not dissected.