First record of the cimicomorphan family Plokiophilidae (Hemiptera, Heteroptera) from China, with description of a new species of Plokiophiloides

Abstract Plokiophiloides bannaensissp. nov., is described from Xishuangbanna, Yunnan Province, representing the first record of the family Plokiophilidae from China. The new species also represents the first record of the genus Plokiophiloides in the Oriental Region, a second zoogeographical region besides the Afrotropical Region. Photographs of the live individuals inhabiting a spider web within natural habitats, male and female habitus, wings of adult, male genitalic structures, female abdomen structures and scanning electron micrographs of forewing, head, thorax and legs are provided. A key to all known species of Plokiophiloides is presented, with a distribution map.


Introduction
The family Plokiophilidae China, 1953 is a small group of true bugs, currently containing nine genera and 20 species (including one Baltic amber fossil genus and one fossil species). Their appearance is reminiscent of the Anthocoridae sensu lato, ranging in External structures and genitalic structures were examined by using a Zeiss Discovery V20 stereomicroscope. Measurements (in mm) were taken using the Zeiss Discovery V20 stereomicroscope with ZEN 2.5 pro software. Male genitalia and the female abdomen were macerated in warm 10% potassium hydroxide solution (KOH). Photographs of habitus, forewing, male genitalia and female abdomen were taken using a Canon EOS 7D Mark II camera, equipped with a tube lens and Mitutoyo M Plan Apo 10× objective lens. Scanning electron micrographs of forewing, head, thorax and legs were prepared using a Zeiss EVO MA 10 at the Instrumental Analysis & Research Center of Sun Yat-sen University. Maps were prepared using SimpleMappr (http:// www.simplemappr.net/).
Abbreviations used in the text and figures are as follows: Plokiophiloides Carayon, 1974: 505. Type species by original designation. Plokiophiloides asolen Carayon, 1974. Comments. The genus Plokiophiloides currently includes four species and can be distinguished from other genera of Plokiophilidae by the following combined characteristics: a) tarsi 2-segmented, b) hemelytron with a distinct cuneus, c) male pygophore tubular, erect, d) fore femora and middle femora without heavy spines on ventral surface, e) posterior margin of pronotum excavated and mesoscutum broadly exposed, f ) male acus shorter than pygophore and its basis simple and g) females without paired external paragenitalia. Diagnosis. The new species can be distinguished from the congeners by the combined characteristics: body with red pigment; exocorium with ca. 65 corial glands; whitish precuneal spot on forewing conspicuous; hypocostal lamina extending caudally as a short, pale whitish-yellow projection.

Plokiophiloides bannaensis
Description. Macropterous male: Small-sized (1.5-1.7 mm), elongate, relatively flat, forewing exceeding apex of abdomen ( Fig. 1A-D). Colouration: Ground colour and head dark reddish-brown, ocelli and ventral surface of head paler. Antennal segment I dark reddish-brown; segment II light brown, distal 1/3 pale yellow, with reddish tinge; segment III brown, distal 1/4 paler, reddish; segment VI brown, distal 2/3 reddish. Labial segments I and II light reddish; segments III and IV yellowish-brown. Pronotum and propleura darker, dark brown to blackish-brown; middle of mesosternum with longitudinal suture, nearly black. Coxae dark reddish-brown; trochanters, femora and tibiae yellowish-brown, sometimes with reddish tinge; tibiae gradually darker to the apices; tarsi brown, basal and distal part paler ( Fig. 1A-D). Corium and clavus light brown to brown, middle part of exocorium and outer part of cuneus dark reddish-brown; basal 2/5 of corium light whitish-yellow; the area around costal fracture and the area of membrane that is behind distal end of cuneus whitish. Membrane light brown, with two inconspicuous longitudinal veins; corial process brown ( Fig. 2A). Posterior margin of abdominal sterna nearly red.
Structure: Head porrect, cylindrical, length subequal to width. Eyes away from collar; minimum dorsal interocular distance greater than 2× the same distance ventrally. Ocelli large, widely separated from each other. Two pairs of strikingly-long setae placed on dorsal surface of head, one pair of setae located in inner part of eyes, at level of anterior margin of eyes, the other located in the posterolateral part of ocelli (Fig. 3E). Antennae thin, terete; segment I thicker than the others, segment II gradually thickening towards the apex, tip of segment IV fusiform; ratio of length of antennal segments I : II : III : IV = 3 : 7 : 7 : 9 (see Table 1). Labium slender, nearly reaching to posterior margin of mesosternum, segment I very short and wide; ratio of length of labial segments I : II : III : IV = 1 : 2.3 : 4 : 7. Thorax: pronotum trapezoidal, with distinct collar, one pair of extraordinarily-long setae placed in dorsal surface of collar; lateral margins of posterior lobe straight; posterior margin strongly excavated, broadly exposed mesoscutum; ratio of maximum length to maximum width = 1 : 2 ( Fig. 3E-G). Costal margin of corium almost straight; hypocostal lamina extending caudally as a short, pale whitish-yellow end; costal fracture deep, almost reaching medial furrow, located ca. 3/4 from the base of corium (Fig. 3A, B). Venation of hind-wing as in Fig. 2B. Legs slender, femora and tibiae without heavy spines on distoventral surface, fore-and middle tibiae with a cleaning comb on apices of ventral surface; tarsi long and slender, 2-segmented, segment I very short, seg-  ment II elongate; claws long, inner claw longer than outer (Fig. 3H). Abdomen: Sterna entire, mediotergites membranous, except for segments I and II with discontinuous remnants of mediotergites and segment VII with a sclerotised medial plate. Abdominal scent gland orifice distinct. Segment VIII with a long, bell-shaped tergum and a U-shaped ventrite. Male genitalia: Pygophore tubular, symmetrical, slightly curved, ventral basal part moderately rounded and bulging. Parameres symmetrical. Phallosoma simple, long. Acus thin, shorter than pygophore, generally curving to the right (Fig. 2D-F).
Macropterous female: Colouration, surface and vestiture and structures of head and thorax as in male. Abdomen: Pregenital segments as in male, except for segment VII-IX with sclerotised, medial plates (Fig. 2C). Female genitalia: No paragenitalia present, boundary of ventrites VIII and IX are unidentified; proctiger simple.
Etymology. The specific name is derived from the abbreviated form of Xishuangbanna, the type locality of the new species.

Discussion
Lifestyle of all species of Plokiophilidae is reviewed in Table 2. Amongst them, only two species of the genus Embiophila were directly discovered in symbiosis with Embiodea. In addition to Plokiophiloides bannaensis sp. nov. (Fig. 4A-C), another eleven species belonging to seven genera were directly discovered in symbiosis with Araneae. Only one species Neoplokiodes raunoi was confirmed to be not associated with webs of spiders or embiids by observations during several expeditions (Štys and Baňař 2016). According to our field observation, individuals of Plokiophiloides bannaensis sp. nov. were found on five spider webs and there were about 5-8 individuals of them on each web. We examined about 30 specimens, including adults and last-instar nymphs, but other instar nymphs and eggs were not found. Adults and last-instar nymphs of web-lovers like to gather near the entrance of the funnel part of webs, which may be convenient for feeding on the remains of the prey of spiders. The new species of Plokiophilidae and its host spider Hippasa sp. are currently only found in tropical China. The geographic distribution pattern of Plokiophiloides is shown in Fig. 5. Plokiophiloides bannaensis sp. nov. was found in the Oriental Region and the remaining four species in the Afrotropical Region. Such an unusual intermittent distribution of Plokiophiloides reminds us that tropical regions between the Afrotropical and Oriental Regions may contain a high diversity of hidden species in this genus. Similarly, three species of Embiophila are separately distributed in the Neotropical and Afrotropical Regions. Therefore, more investigation is needed to clarify the species diversity and thus the distribution pattern of Plokiophilidae in pantropical regions.  Carayon, 1974 CG unknown unknown, the specimens were collected in soil samples Carayon 1974 Plokiophiloides steineri Štys, 1991 MG unknown unknown, the specimens were collected in flight interception traps Štys 1991 Notes