Medleria gen. nov. adds to the biodiversity of Flatidae (Hemiptera: Fulgoromorpha) in the island of Socotra

A new monotypic genus of fl atid planthoppers (Hemiptera: Fulgoromorpha: Flatidae), Medleria gen. nov., is described for Medleria caudata gen. et sp. nov. (type species) from the island of Socotra (Yemen). Habitus, male and female external and internal genital structures of the new species are illustrated and compared with similar taxa. Medleria caudata gen. et sp. nov. is probably endemic to Socotra where it is known to date from a small area of the Dixam mountain plateau only.


Material and methods
The material studied is deposited in the entomological collections of the institutions detailed below.
Label information of all specimens examined is in square brackets and provided verbatim with each line separated by a slash (/).

Preparation and illustration
The abdomens of the specimens examined were removed and cleared for 30 minutes in a warm solution (50°C) of 10% KOH, with a few drops of chlorazol black (CAS No. 1937-37-7) for dying the ectodermic structures based on the method introduced by Carayon (1969) and Bourgoin (1993). Dissections and cleaning of genital structures were performed in distilled water. Final observations and drawings were done in glycerol using a camera lucida attached to a light microscope. All colour images were taken using a stereo microscope Leica MZ 16 with a digital camera IC 3D; fi nal images were produced using Helicon Focus and Adobe Photoshop software. The SEM photographs of uncoated specimens were taken in the Laboratory of Scanning Microscopy, Museum and Institute of Zoology, Polish Academy of Sciences (Warsaw), using a scanning electron microscope HITACHI S-3400N under low vacuum conditions.

Measurements and abbreviations
Measurements were taken with an ocular micrometer. The following measurements, ratios and their abbreviations were used in this study: Total length = length of specimen from head apex to tegmina apex (in dorsal view) A / B = width of vertex at anterior margin / length of vertex at midline C / E = width of frons at upper margin / length of frons at midline D / E = maximum width of frons / length of frons at midline F / B = length of pronotum at midline / length of vertex at midline G / F = length of mesonotum / length of pronotum at midline G / B+F = length of mesonotum / cumulative length of vertex and pronotum at midline G / H = length of mesonotum at midline / width of mesonotum between lateral angles I / J = length of tegmen from the base to the sutural angle (end of "tail") / width of tegmen at the widest part

Diagnosis
The new genus differs from similar fl atid taxa so far known from Socotra, the Middle East and Africa by the following characters: vertex short and broad, lacking carinae or grooves on its disc (Figs 1E, 2C-E); frons broad, tricarinate with median and lateral carinae basally separated (Figs 1D, 3C-D); mesonotum with double median carina (Figs 2C-D, 3A-B); sutural angle of tegmen produced into a short, apically subacute, fi nger-like tail covered with tubercles and sensory structures (Figs 2A, 4A-F); male anal tube deeply split dorsally (Figs 5C-D, 6B), with obtuse apical lobe oriented ventrad (Figs 5A-B, 6A); periandrium with single appendage on each side subapically which is strongly curved apicad and ramifi ed into four well-sclerotized, long spine-like processes ( Fig. 6D-E).

Etymology
The genus is named to honour Dr. John T. Medler (1914Medler ( -2006, an outstanding expert in the taxonomy of the world Flatidae. Gender feminine.

Description
HEAD. Head with compound eyes, in dorsal view, broad, slightly narrower than thorax (Figs 1B, E, 2B-C, E). Vertex transverse, distinctly narrower and shorter at midline than pronotum, with all margins carinate; disc of vertex without carinae (Figs 1E,. Frons widest at its basal (lowest) third, with upper margin almost straight; lateral margins arcuate and elevated, in median portion partly fl attened, without incisions, in lower part strongly curved to frontoclypeal suture; disc of frons tricarinate, all carinae basally separated; frontoclypeal suture slightly arcuate (Figs 1D, 3C-D). Clypeus smooth, without carinae (Figs 1D, 3C-D). Rostrum with apical segment shorter than subapical one, apex reaching between hind coxae (Fig. 3F). Compound eyes elongately oval, with very small callus at posterior margin. Lateral ocelli present (Fig. 1C). Antenna inserted very close to medio-ventral margin of eye; scapus small, ring-like, without setae; pedicel shorter than diameter of eye but distinctly longer than scapus, club-like, apical part concave, functional area at the top and on dorsal surface with trichoid sensilla type 1, antennal plate organs present on apical concavity and basally delimiting lateral margins of dorsal functional surface ( Fig. 3D-E).
THORAX. Pronotum shorter than mesonotum at midline; anterior margin surpassing the midlength of compound eyes in dorsal view; pronotum disc with depression alongside anterior margin, median gibbosity and lateral impressions; postocular eminences crest-shaped with acute top (Figs 1B, E, 2C-F). Mesonotum with scutellum widely deltoid, wider than long at midline; disc of mesonotum with double median carina medially separated by deep groove; lateral carinae arcuate, reaching posterior margin; scutellum fl at with acute, elevated apex (Figs 1E, 2C-D, F). Tegmen coriaceous, partly convex, longer than wide, with distinct venation apart from apical part, tapering apicad; costal margin strongly arcuate, costal angle widely rounded, sutural angle produced in a form of short tail covered with tubercles and sensory structures, postclaval sutural margin long ( . Costal area as wide as postcostal cell, with transverse veinlets, terminating at the level of end of clavus; area between veinlets membranous, each with one or two tubercles; postcostal cell with one transverse veinlet in apical part; apical line absent (Figs 2A with labelled longitudinal veins, 4A). Basal cell long and narrow; ScRA+RP leaving basal cell with short common stem; ScRA elevated, passing the top of bulla; RP in basal part obsolete, with fi rst fork before posterior margin; MP forking after Cu fork but before claval veins joint, MP terminals ending in the tail of tegmen; CuA terminals ending at postclaval margin, anterior to tail. Clavus in basal half elevated and covered with tubercles , posterior part concave, without tubercles; A 1 weakly elevated; Pcu and A 1 joined slightly anterior to clavus apex. Whole tegmen covered with scattered tubercles with their concentration in the following parts: transverse veinlets of costal area, bulla between ScP+RA, RP and MP, basal part of clavus -between Pcu and A 1 , and A 1 and A 2 ( LEGS. Pro-and mesotibia with shallow groove on external side, about as long as pro-and mesofemur, respectively; apical tarsomere of both legs longer than cumulative length of second and basal tarsomeres. Metatibia longer than metafemur, with two lateral spines placed close to each other in distal part and apical row of spines; basitarsomere of metatarsus about as long as cumulative length of second and apical tarsomeres, with apical spines V-lined; second tarsomere with lateral spines and median pad with setae. MALE TERMINALIA. Anal tube, in lateral view, distinctly elongate, basal part narrower than apical part; anus placed anterior to midlength; apical part with obtuse lobe projected ventrad (Figs 5A-B, 6A); in dorsal view, anal tube elongate and narrow; basal part constricted laterally, apical part with deep split dorsally, closed ventrally (Figs 5C-F, 6B). Pygofer, in lateral view, subrectangular, dorsal margin shorter than ventral margin, anterior margin sinuate, posterior margin produced into a lobe forming obtuse angle postero-dorsally (Figs 5A-B, 6A). Genital style longer than wide, widening apicad, bearing long and straight capitulum with subacute apex oriented dorsad (Figs 5A-B, E-F, 6A, C). PHALLIC COMPLEX. Periandrium elongate, almost straight, as long as aedeagus, apical part narrower than basal part; lateral split distinctly exceeding midlength (Fig. 6D-E). Dorsal part of periandrium, in lateral view, longer than ventral part, widening apicad, with single appendage on each side subapically; appendage strongly curved apicad with four well sclerotized, long spine-like processes; dorsal side apically membranous with three small lobes ( Fig. 6D-E). Ventral part of periandrium unilobate, tapering apicad, with curved apex; ventral side with distinct triangular keel (Fig. 6F). Aedeagus, in lateral view, long and curved, with apical, bulb-like, sclerotized appendages; in ventral view, with deep median split, not exceeding midlength, lateral parts connected with membrane ( Fig. 6G-H). FEMALE TERMINALIA. Pregenital sternite with asymmetrically X-shaped sclerotization; upper arms shorter than lower ones, median portion weakly sclerotized; lateral lobes separated (Figs 7E-F, 8A-B, 9A). Anal tube, in lateral view, covering gonoplac and reaching its posterior margin; basal part wider than apical part (Figs 7C-D, 9C); in dorsal view, elongately oval (Figs 7A-B, 9B). Gonoplac elongate, oriented horizontally, not covering gonapophysis VIII (Figs 8C, E-F, 9E-F); posterior margin with two rows of alternately placed teeth -large internally and small externally; large teeth of both gonoplacs fi tting together in a zip-like manner (Fig. 8D). Gonoplac divided by strongly sclerotized strip into two parts -dorsal and ventral; ventral membranous part very narrow, extending from the teeth to base (Fig. 9E). Gonapophysis VIII relatively slender and narrow, curved, laterally fl attened (Fig. 9D); median part of dorsal margin and subapical part of ventral margin with a few (3-4) teeth; endogonocoxal process as long as gonapophysis, tapering apicad, with fi nger-like apex and spiniferous microsculpture on internal side. Gonospiculum as in Fig. 9G-H. Bursa copulatrix with single pouch, kidney-shaped, cells with weakly sclerotized central areas with microsculpture on the surface (Fig. 9I). Spermatheca well developed, ductus receptaculi longer than diverticulum ductus (Fig. 9J).

Diversity and distribution
The genus is described as monotypic for a single species from Socotra Island.

Diagnosis
The only species in the genus; see diagnosis for the genus.

Etymology
From the Latin adjective 'caudatus' (= tailed, caudate). The specifi c epithet refers to the prolonged apical part of the tegmen. area between median and lateral carinae depressed (Fig. 2C-F). Tegmen: I / J = 1.59-2.08. Metatibia with apical row of seven well-developed spines, external spines longer than ventral ones; basitarsomere with 7 apical spines; second tarsomere with two lateral spines. MALE TERMINALIA. Anal tube, in lateral view, with ventral margin weakly convex and dorsal margin weakly concave in median portion, postero-dorsal angle right (Fig. 5A-B). Genital style with posterior margin straight, ventral and dorsal margins almost straight, subparallel, postero-ventral angle bluntly rounded, not extending the posterior margin ( Fig. 6A-C). Appendage of dorsal periandrium with well-sclerotized small teeth in its median curved part (Fig. 6E). Dorsal part of aedeagus membranous (Fig. 6G). FEMALE TERMINALIA. Pregenital sternite with posterior margin convex medially, anterior margin concave (Fig. 9A). Anal tube, in lateral view, tapering apicad, with bluntly rounded apex; anus placed anterior to midlength; ventral margin medially weakly arcuate (Fig. 9C); in dorsal view, anal tube widest in its median portion, apically truncate, posterior margin almost straight (Fig. 9B). Gonoplac with its dorsal part with membranous base, strongly sclerotized median portion and two rows of teeth placed posteriorly-external teeth small and fl at, internal teeth huge and hook-like; ventral part weakly sclerotized (Figs 8D, 9E). Gonapophysis VIII with dorsal margin bearing three teeth, ventral  margin subapically slightly up-folded with four teeth; basal part of gonocoxal process with strongly sclerotized strip (Fig. 9D). Spermatheca with ductus receptaculi not divided into two parts, ribbed, widened apically; diverticulum ductus smooth, with narrow basal part and elongate apical bulba (Fig. 9J). Two large eggs (1.2 mm) in ventro-dorsal position were discovered during dissection of the female abdomen.

Host plant and habitat
The type series was collected by beating shrubs on a warm and sunny day, in a sparse semi-arid shrubland on a coarse, stony substrate of a montane limestone plateau (Fig. 10A-B). The vegetation was almost uniformly composed of Croton cf. socotranus Balf. f. (Euphorbiaceae). This plant species is thus a probable host of M. caudata gen. et sp. nov. (Fig. 10C).

Discussion
There are currently eight described fl atid species from Socotra, including Medleria caudata gen. et sp. nov. The newly described taxon can be easily distinguished from the seven previously known species by the combination of its body size, shape and coloration, as well as the structure of the head, thorax, tegmen, and male and female terminalia and genitalia. The most similar taxa are two other monotypic genera, Dixamfl ata and Kesafl ata. Medleria gen. nov. shares with them a more or less similar size (Dixamfl ata petri Stroiński, Malenovský & Świerczewski, 2016 is slightly smaller, Kesafl ata lubosi Stroiński, Malenovský & Świerczewski, 2016 slightly larger than M. caudata gen. et sp. nov.), lightbrown general coloration with dark markings, strongly bulged bulla and clavus, and coriaceous and relatively short tegmina giving the specimens an issid-like habitus. However, M. caudata gen. et sp. nov. differs from both D. petri and K. lubosi by the following characters: -a short and broad vertex lacking carinae or grooves on its disc (Figs 1E, 2C-E); D. petri has the head anteriorly produced into a conspicuous semicircular crown (Stroiński et al. 2016: fi gs 4, 7, 12-13), K. lubosi has a short, but narrow vertex with a median groove (Stroiński et al. 2016: fi gs 57, 62); -wide frons with three distinct keels widely separated at base (Figs 1D, 3C-D); the frons is relatively narrow with obsolete lateral (= intermediary) keels in D. petri (Stroiński et al. 2016: fi gs 6, 16) and relatively narrow with three distinct keels connected at base in K. lubosi (Stroiński et al. 2016: fi gs 56, 65); -mesonotum with a double median carina (Figs 2C-D, 3A-B), in contrast to a single median carina in D. petri (Stroiński et al. 2016: fi gs 12-13) and a shallow groove in K. lubosi (Stroiński et al. 2016: fi gs 61-63); -longer tegmen apex (sutural angle) which is upturned, fi nger-like, subacute and covered with tubercles and sensory structures (Figs 2A, 4A-F); similar sensory structures on the tegmen apex which is, however, less produced are present also in D. petri (Stroiński et al. 2016: fi gs 22-23, 25, 27-28); they are absent in K. lubosi which has the tegmen apex short and more broadly rounded (Stroiński et al. 2016: fi gs 53, 58-59); -male anal tube deeply split dorsally (Figs 5C-D, 6B) and with a relatively broad obtuse apical lobe oriented ventrad (Figs 5A-B, 6A); apex of the male anal tube is less deeply split dorsally and, in lateral view, narrow and not produced ventrally in D. petri (Stroiński et al. 2016: fi gs 31-35); this character as well as the three following ones are unknown in K. lubosi which was described only from a female; -male pygofer in lateral view produced into an obtusely angled postero-dorsal lobe (Figs 5B, 6A); in D. petri, it is nearly regularly arcuate (Stroiński et al. 2016: fi gs 31-32, 35); -male genital style, in lateral view, with a rounded ventro-apical angle (Fig. 6A, C); in D. petri, it bears a small tooth-like ventro-apical process on inner side (Stroiński et al. 2016: fi g. 35); -periandrium on each side with a subapical appendage ramifi ed into four spines (Fig. 6D-E), in contrast to a one-armed process in D. petri (Stroiński et al. 2016: fi gs 36-37); -female gonapophysis VIII relatively slender and narrow, with dorsal margin bearing teeth medially but not subapically (Fig. 9D); in Dixamfl ata and Kesafl ata, it is relatively broader and its dorsal margin bears teeth only subapically (Stroiński et al. 2016: fi gs 48, 73); -female gonapophyses IX with slender and acute apices (Fig. 9G-H); in both Dixamfl ata and Kesafl ata, their apices are more robust and blunt (Stroiński et al. 2016: fi gs 49-50).
Within the fauna of a wider region, i.e., Africa and the Middle East, Medleria gen. nov. superfi cially resembles four fl atid genera also sharing an issid-like habitus: Cyphopterum Melichar, 1905, Riodeorolix Lindberg, 1956, Afrophantia Fennah, 1958 and partly also Persepolia Dlabola & Safavi, 1972. Medleria gen. nov. differs from these taxa in having a distinctly tricarinate frons (Afrophantia, Cyphopterum and Riodeorolix have just the median carina present, Persepolia has the carinae on frons obsolete), double median carina on mesonotum (single or partly obsolete in all four other genera), and details of the male terminalia, particularly of the pygofer, anal tube and periandrium including its appendages (Lindberg 1953(Lindberg , 1956(Lindberg , 1962(Lindberg , 1963Fennah 1958;Dlabola & Safavi 1972;Dlabola 1982;Leise & Remane 1994;Medler 2001;Stroiński et al. 2016). A detailed morphological redescription of some of these genera and a phylogenetic analysis including also a representative number of other taxa of Flatidae is needed to test if these superfi cially similar taxa are also closely related.
Like all other fl atid species previously described from Socotra, M. caudata gen. et sp. nov. is currently known from this island only. As it is sub-macropterous, its dispersal ability might be reduced. We also suppose that it is trophically associated with the shrub species Croton cf. socotranus which is endemic to Socotra (Brown & Mies 2012). Medleria caudata gen. et sp. nov. may thus represent a species endemic to Socotra as well. Moreover, its distribution on the island may be very restricted -despite a fairly intensive sampling of C. cf. socotranus at many different localities throughout the island (I. Malenovský, L. Purchart, pers. obs.), M. caudata gen. et sp. nov. was recorded only once at a single place on the Dixam montane plateau. The Dixam Plateau and the adjacent Hagh er Mountains in central Socotra are well-known for a high concentration of many endemic plants restricted to this part of the island (Miller & Morris 2004;Brown & Mies 2012). Two other presumably endemic fl atid species, Dixamfl ata petri and Kirkamfl ata socotrana have also been described from this region (but other habitats and host plants; Świerczewski et al. 2014;Stroiński et al. 2016). Like these two species, M. caudata gen. et sp. nov. may also be imminently threatened by extinction due to habitat degradation, especially by overgrazing and timber harvesting, the intensity of which has been increasing in recent years (van Damme & Banfi eld 2011; Brown & Mies 2012). Detailed fi eld work is therefore needed in the near future to reveal the distribution of these planthopper species in Socotra more completely, to describe their ecological requirements, and to plan for their effi cient conservation.