Plinthisus (Nanoplinthisus) drakensbergensis, Sweet, Merrill H. & Slater, James A., 2004

Sweet, Merrill H. & Slater, James A., 2004, An analysis of species­groups of the genus Plinthisus Stephens (Hemiptera: Rhyparochromidae) in the Ethiopian Region with the description of eight new species, Zootaxa 533, pp. 1-56 : 36-40

Plinthisus (Nanoplinthisus) drakensbergensis n. sp.

(17, 19, 37, 48, 65, 79, 98, 99, 109, 121)

Description. Brachypterous male. General coloration translucent bright honey­yellow, becoming slightly darker yellow­brown on hemelytra and castaneous on abdomen. Antennae brownish. Surface shining and polished, appearing impunctate. Dorsal surface and abdomen thickly covered with elongate semi­upright posteriorly­directed hairs, each in a micropuncture, micropunctures more evident on scutellum; hairs nearly equal in length to antennal hairs. Long trichobothriumlike seta on eye, proximal outside surface of protibia, and lateral margin of pronotum, 1/3 distance from humeral corner, pair on vertex 0.12 long 0.17 apart, 0.07 from eye; shorter seta on eye, tylus, gena and antenniferous tubercle. Abdominal sterna with 2 trichobothria on each side of meson of 3, anterior hair long; 1 trichobothrium on 4, more lateral in position; anterior trichobothrial hairs of 5 and 6 and dorsal posterior trichobothrial hair of 6 long (0.18), others as short as body hairs; posterior pair on 5 oblique, close together (0.01) just caudad of spiracle, 0.04 from posterior margin of sternum; pairs on 6 and 7 further apart (0.03). Head slightly declivent, acuminate, strongly convex across vertex. Tylus extending to distal 1/3 of 1st antennal segment. Tylus nearly flat, hardly elevated above juga, length 0.14, width 0.06. Tylar sutures incised, converging caudad, then recurving slightly at ends. Juga gently convex, apices acute. Lorum and gena concave. Antenniferous tubercles invisible from above, insertions below and in front of eyes. Eyes almost in contact with anterolateral pronotal angles. Eye small, of 25 facets, length 0.05, height 0.11. Ocelli absent. Bucculae very low, inflated, height much less (0.02) than width of labial segment; very short, becoming ridges at level of apices of juga; ridges flaring and terminating posteriorly in a broad "U" at base of head. Telescoped head slightly swollen ventrad, length 0.12. Visible head length 0.22, width across eyes 0.36; interocular space 0.28, height above eye 0.05, height below eye, 0.04, preocular distance 0.13, postocular distance 0.005.

Pronotum broadest across anterior 1/3, moderately arcuate laterad, evenly narrowed caudad. Lateral margins sharply carinate; anterior margin gently concave; posterior margin nearly straight, barely overlapping hemelytron. Dorsal collar and posterior lobe indistinct [visible on clearing], not delimited by sulcus or puncturation. Anterior lobe moderately convex, height above lateral margin 0.07. Pronotum medial length 0.37, [posterior lobe length 0.07 (cleared)]; maximum width 0.50, width across humeri 0.47; [collar length 0.06 (cleared)]. Scutellum flat; length 0.18, width 0.37. Mesoscutum continuous with mesepisternum and set off by shining sulcus from scutellum [especially visible in females.] Hemelytron pad­like, clavus and corium indistinguishably fused; hinge absent; membrane remnant absent. Base of hemelytron not fused to mesonotum or scutellum, compressed at level of sulcus. Caudal (distal) hemelytral margin truncate, straight, at right angle to longitudinal body axis, covering only 3rd abdominal tergum, and leaving 4th tergum completely exposed. Hemelytral laterocaudal corners rounded, lateral margins broadly arcuate, ecarinate, narrowly clasping pterothorax ( Fig. 27 ). Hemelytron much wider than maximum pronotal width, maximum width 0.34, length 0.46; commissure length 0.24; distance caudal (distal) margin of hemelytra to apex abdomen 0.60. [Metanotum short, pale, weakly sclerotized, not extending caudad of scutellum. Metathoracic wing ( Fig. 37 ) very reduced, width 0.085, length 0.103. Stridulitrum oval, width 0.057, length 0.062, with 40 teeth, each 5–6 µ wide in 6 oblique rows.] Propleural pore ( Fig. 27 ) very small but distinct, nearer to pleural suture than collar sulcus. Posterior lobe of proepimeron and mesepisternum compressed, impunctate. Mesepimeron and metepisternum ecarinate below groove receiving hemelytron ( Fig. 27 ). Metathoracic scent gland auricle ( Fig. 27 ) extending caudad for most of its length, recurving at distal end to point cephalad; apex of auricle acute, posterior margin sharp, raised above scent area. Granulose scent area covering most of metepisternum and margin of mesepimeron, leaving only a narrow shiny dorsal area. Metapleural flange set off by shallow sulcus; posterior margin of flange straight. Prosternum convex, length 0.32; ventral collar set off by sulcus which ends at lateral carina, collar length 0.09; proxyphus small, pointed. Mesosternum transversely rugulose, anteriorly with a low median carina, posteriorly with small tumosity; mesoxyphus low, apex truncate, fused with metasternum. Metasternum with low median carina, metaxyphus narrow, barely truncate. [Metacoxal bridges narrow. Mesendosternite and mesendotergite equally short, with ends splayed flat, and remote from each other.] Abdomen oval; maximum width 0.61, length 0.65. Connexivum uptilted, visible terga gently arched, caudal margin of tergum 7 rounded ( Fig. 48 ). [Abdominal sternal sutures 2–3, 3–4, 4–5 very finely dovetailed; sutures 3–4 and 4–5 bent slightly cephalad at level of trichobothria. (In female, intersternal margins straight.) Spiracle 5 and 6 each a similar distance (0.07) from anterior and posterior margins of sternum. Tergum 1 ( Fig. 48 ) with plectra angled mesad; plectrum small, width 0.04, length 0.04; extremely finely striate, striae anteriorly 0.3 µ apart, posteriorly <0.2 µ apart, near the resolution of the light microscope. Tergum 2 nearly desclerotized; with two lateral apodeme­like sclerites. Tergum 1 narrow, width 0.40. Tergum 3 short, slightly convex cephalad, little longer in middle; strong ridge­like transverse carina along posterior margin. Tergal sutures 4–5 and 5–6 not dovetailed, sutures curving caudad so that tergum 6 is shorter than terga 4, 5 or 7. Maximum width of terga 0.54; medial lengths of terga: 1­0.05, 2­0.06, 3­0.07, 4­0.20, 5­0.22, 6­0.12, 7­0.17. Scent gland scar widths: 3­4: 0.21, 4­5: 0.15, 5­6: 0.16. Terga 4–7 inflexed and grooved laterad to receive mesal margin of connexivum. Epipleurites 3–6 very narrow, 0.005 in width. Connexivum relatively narrow, hypopleurite widths: 2­0.03, 3­0.06, 4­0.07, 5­0.06, 6­0.06, 7­0.04; lengths: 2­0.03, 3­0.07, 4­0.15, 5­0.17, 6­0.22, 7­0.14. Hypopleurite junctions nearly transverse. Tergum 7 internally impressed and sternum 7 with lateral shelves to receive segment 8 and genital capsule. Sternum 7 with 2 widely separated short anterior apodemes 0.18 apart. Genital capsule ( Fig. 59 ) width 0.25; posteriorly flattened, posterior rim ecarinate; parandria short, slender and bluntly pointed; dorsal opening large, nearly as wide as clasper opening. Epiproct faintly sclerotized, relatively long, setulose; paraprocts slender, meeting ventrad; dorsal and ventral anal sclerites fused together mesad, ventral sclerite broader, bearing eight setae. Clasper ( Fig. 79 ) shank straight, with sharp spine on outer projection; blade straight, short, strongly carinate on inner (frontal) face. Phallus ( Fig. 71 & 72 ) with gonoporal process of 4 basal coils with membranous sleeve, and 5–6 thin distal coils; helicoid process absent. Sperm reservoir dorsally desclerotized; wings large, triangular, folded down and pointed slightly distad; holding sclerites short and broad. Phallotheca with two ventrolateral and two dorsal sclerotized bars. (In female, tergum 1 and 2 desclerotized; tergum 3 moderately convex cephalad, longer in middle, length 0.12; a distinct carina along posterior margin. Epipleurite 3 very small. Tergum 6 and 7 indistinguishably fused. Tergum 8 with 2 anterior submesal sutures meeting 1/3 distance from caudad margin. Tergum 9 small with long medial anterior apodeme; epipleurite 9 large, without apodeme. Valvula length 0.43. Spermatheca (Fig. 109) uniquely shaped, with subhemispherical bulb; sclerotized distal duct wide below bulb, constricted, then greatly expanded into a doughnut­shaped sac with a wide duct which leaves sac laterad; unsclerotized basal duct very long, narrow, widened basad.)]

Profemur (Fig. 121) moderately incrassate, length 0.49, width 0.22; convex above and below; mutic. Protibia moderately bent, inner face with 6 small tubercles; distal end armed with blade­like flat outer (posterior) spine, and a spur inside; protibial length 0.38, distal width 0.09. Meso­ and metatibia each with row of 3 small spurs; metatibia length 0.43, medial width 0.04, lengths of metatarsomeres: I 0.12, II 0.05, III 0.07. Labium extending between mesocoxae, 1st segment attaining or nearly attaining base of head; labial segment lengths: I 0.20, II 0.22, III 0.18, IV 0.18. Antennae short, stout, segment 1 terete, and 2, 3, and 4 fusiform; width 0.07; antennal segment lengths: I 0.15, II 0.29, III 0.22, IV 0.25. Total body length 1.59.

Material examined. HOLOTYPE: Brachypterous male. SOUTH AFRICA: Natal, Olivierhoek Pass summit, 5400', 25 mi. South of Harrismith, 4.III.1968 (J.A. & S. Slater, T. Schuh, M.H. Sweet, no. 201). In National Collection of Insects, Pretoria, South Africa.

PARATYPES: (all brachypterous) 8 m 6 f (2 m, 2 f dissected). Same data as holotype. In M.H. Sweet and J.A. Slater collections.

Etymology. Drakensberg is Afrikaans for mountain of the dragons, ­ensis, a suffix meaning from the place of. The Drakensberg forms a great wall of mountains separating the South African high plateau from the Natal coastal plain. The name is evocative of the isolation of this species, which appears unrelated to any other species­group of Plinthisus .

Discussion. As noted, P. drakensbergensis superficially resembles P. zuurbergi , but it is actually not closely related and appears to be endemic to the Drakensberg Massif. It also does not show close relationship to the other minute shiny Plinthisus in South Africa, the Fynbosi group, which also has mutic profemora and an ecarinate hemelytra, because in P. drakensbergensis : 1) the scent auricle recurves cephalad ( Fig. 27 ) rather than curving caudad ( Fig. 23 ); 2) the clasper is short and straight with a carinate blade ( Fig. 79 ), not ecarinate and offset laterad on the shank ( Fig. 73 ); 3) the posterior rim of the genital capsule is ecarinate ( Fig. 59 ), not carinate ( Fig. 60 & 61 ) 4) the dorsum is hirsute, not nearly nude; and 5) the spermatheca is bizarre (Fig. 109), contrasting with the relatively simple spermathecae of species­groups Fynbosi and Zuurbergi ( Figs. 105 & 108 ). It is therefore very likely that the general external similarity of P. drakensbergensis with the Fynbosi and Zuurbergi species­groups is due to convergence.

We place the Drakensbergensis group in Wagner's subgenus Nanoplinthisus because the hemelytron lacks a membrane remnant, and is truncate at the level of tergum 3; the clasper is straight with a carinate blade; and the body length is under 1.8 mm.

It is probable that these tiny shining species of Plinthisus , which look so much like each other, not only among those in South Africa, but also with species in Australia, South America, Western North America, and Europe, are similar through convergence for living in tiny crevices, but are actually unrelated as shown by the remarkable internal differences, especially in the genitalia. Phylogenetically, these species­groups will probably become different genera despite their apparent close external similarity.

Figures

FIGURES 18 – 27. Mesopleuron and metapleuron, male. 18, P. rudebecki. 19, P. hirsutus. 20, P. brachyoccus. 21, P. pulchellus. 22, P. e r i c a e. 23, P. fynbosi. 24, P. peninsularis, 25, P. lamprus. 26, P. z u u r b e rg i. 27, P. drakensbergensis. Abbreviations: au—auricle, hm—hemelytron, mf – metapleural flange, mp—mesepimeron, mps—mesopleural sulcus, ms – mesepisternum, mt—metepisternum, sa—scent area, tls – trichobothriumlike setae. Figures 24 to 27 on the next page.

FIGURES 28 – 37. Male right metathoracic wing, ventral view, 28, P. brachyoccus, macropter, including Fig. 28 a, detail of overlapping stridulitra of wings at rest. Figs 29 – 37, brachypterous metathoracic wings. 29, P. rudebecki. 30, P. hirsutus. 31, P. pulchellus. 32, P. e r ic a e. 33, P. fynbosi. 34, P. peninsularis. 35, P. lamprus. 36, P. z u u r b e rg i. 37, P. drakensbergensis. Abbreviations: Cu—Cubitus, h—hamus, IV—Intervannal veins, M— Medius, mnt—metanotum, mtws—metathoracic wing stridulitrum, Pcss—Postcubital sector stridulitrum, R— Radius, Sc—scutellum, st—stridulitrum, te—teeth. Figures 29 to 37 on the next page.

FIGURES 38 – 50. Abdomen structures. 38 (p. 48), lateral view, male, P. e r ic a e. 39 – 48, left dorsal view, male. 39, P. rudebecki. 40, P. hirsutus. 41, P. brachyoccus. 42, P. pulchellus. 43, P. e r i c a e. 44, P. fynbosi. 45, P. peninsularis. 46, P. lamprus. 47, P. zuurbergi. 48, P. drakensbergensis. 49 – 50, dorsal abdominal segments 5 – 8, female. 49, P. pulchellus. 50, P. fynbosi. Abbreviations: e—epipleurite of connexivum, h—hypopleurite of connexivum, oj— oblique juncture of hypopleurites 4 & 5, pl—plectrum on tergum one, sg—scent gland scar, sp – spiracle, spl—secondary plectrum, St 3 — sternum 3, St 7 — sternum 7, Tg 2 — tergum 2, Tg 6 — tergum 6, Tg 7 — tergum 7, tr—trichobothrium. Figures 44 to 50 on the next page.

FIGURES 51 – 65. Genital capsule, dorsal view (d. v.), lateral view (l. v.). 51, P. hirsutus, d. v. 52, P. hirsutus, l. v. 53, P. pulchellus, d. v. 54, P. brachyoccus, d. v. 55, P. brachyoccus, l. v. 56, P. lamprus, d. v. 57, P. e r i c a e, d. v. 58, P. e r i c a e, l. v. 59, P. drakensbergensis, d. v. 60, P. fynbosi, d. v. 61, P. fynbosi, l. v. 61 a, P. rudebecki, d. v. 62, P. peninsularis, d. v. 63, P. peninsularis, l. v. 64, P. z u u r b e rg i, d. v. 65, P. zuurberg, l. v. Abbreviations: ap—accessory sperm pump, as—anal sclerites, cl—clasper in place, co—clasper opening, do—dorsal opening, epepiproct, p—parandria, pa—paraprocts, pr—posterior rim. Figures 62 to 65 on the next page.

FIGURES 66 – 79. Left clasper, area of attachment down, frontal view, except 70 and 76, lateral view (l. v.). 66, P. rudebecki. 67, P. hirsutus. 68, P. brachycoccus. 69, P. pulchellus. 70, P. pulchellus l. v. 71, P. (Isioscytus) himyaritus Linnavuori, 1978. 72, P. eri ca e. 73, P. fynbos. 74, P. fynbos, l. v. 75, P. (Nanoplinthisus) muticus Slater, 1964. 76, P. peninsularis. 77, P. lamprus. 78, P. z u u r b e rg i. 79, P. drakensbergensis. Abbeviations: aarea of attachment, b—blade, i—inner projection, o—outer projection, s—shank, tp—tip.

FIGURES 100 – 108. Spermatheca. 100, P. rudebecki Slater. 101, P. hirsutus Slater. 102, P. brachyoccus. 103, P. pulchellus. 104. P. e r i c a e. 105, P. fynbosi. 106, P. peninsularis. 107, P. lamprus. 108, P. z u u r b e rg i. 109, P. drakensbergensis. Abbreviations: bd—basal duct, bu—bulb, dd—distal duct.