Plinthisus (Isioscytus) pulchellus
Creators: name: Sweet, Merrill H.
name: Slater, James A.
Publisher: name: Zenodo
Year: 2004
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Hemiptera
Rhyparochromidae
Plinthisus
Plinthisus pulchellus

description: Plinthisus (Isioscytus) pulchellus n. sp
(Figs. 1, 2, 11, 21, 31, 42, 53, 69, 70, 86. 87, 103, 115)
Description. Brachypterous male (Fig. 2). General coloration black to dark chocolate brown. A prominent broad oblique light yellowish­brown bar running from outer basal angle of hemelytron caudo­mesad to level of apex of scutellum, separated from lateral margins of scutellum by slightly less than width of bar. Antennae nearly uniformly dark brown, somewhat paler on distal 1/2 of 1st and distal 1/3 of 2nd segments. Femora and tibiae dark brown. Distal ends of tibiae and tarsi and lateral margins of hemelytra ventrad of carinate margins above pleura testaceous. Coxae, trochanters and acetabular area bright red­brown. Body surface polished, strongly shining, proepisternum especially highly polished. Posterior lobe of pronotum, proepimeron, mesopleuron, dorsal 1/3 of metepisternum, scutellum, and hemelytra coarsely and deeply punctate; mesepimeron rugulose. Head and extreme anterior area of pronotum with minute inconspicuous punctures; remainder of anterior lobe of pronotum and metapleural flange smooth and nearly impunctate. Pronotum and hemelytra with scattered, decumbent short sericeous hairs. Antennae clothed with long conspicuous, forward­directed hairs. Long slender trichobothriumlike seta (Fig. 11) on eye, antenniferous tubercle, and apex of tylus, pair on vertex 0.10 long, 0.15 apart, distance from eye 0.05. [Abdomen with cluster of 3 trichobothria on each side of meson of sternum 3, one trichobothrium on each side of sternum 4; anterior trichobothrial hair of sterna 5 and 6 and dorsal hairs of posterior pair of 6 and 7 very long (0.21); posterior pair of hairs on 5 oblique, placed directly below spiracle, 0.04 from posterior margin of sternum.]
Head (Fig. 11) slightly declivent, acuminate, moderately convex across vertex. Tylus attaining distal 1/3 of 1st antennal segment. Tylus moderately convex, length 0.10, width 0.07. Tylar sutures incised, subparallel. Juga posteriorly concave, anteriorly nearly flat, apices obtusely acute. Lorum concave, polished, with a slight carina along jugal suture. Antenniferous tubercles relatively large, visible from above; insertion of antennae below and directly in front of eye. Ocelli very small (dia. 0.006). Eyes extending laterad to level of anterior pronotal angles. Eye oval, relatively large, of about 90 facets; length 0.09, height 0.14. Bucculae (Fig. 11) low, height less (0.03) than width of labial segment 1, becoming ridges before level of antenniferous tubercles, ridges terminating in a "U" before caudal margin of head. Telescoped posterior part of head dorsally very polished, iridescent (possibly a strigil), ventrally enlarged, length 0.14. Visible head length 0.22, width across eyes 0.36; interocular space 0.23, height above eye 0.06, below eye 0.04, preocular distance 0.13, postocular distance 0.01.
Pronotum (Fig. 2, 11) broadest across anterior lobe; lateral margins sharply carinate, very slightly sinuate; anterior and posterior margins nearly straight. Dorsal collar weakly delimited by row of small punctures. Posterior lobe weakly differentiated by punctation and sinuation. Dorsum of anterior pronotal lobe moderately convex; height above lateral margin 0.04. Pronotal medial length 0.34, posterior lobe length 0.15, maximum width 0.50, width across humeri 0.48; [dorsal collar length 0.03 (cleared)]. Scutellum slightly convex; length 0.20, width 0.33. [Mesoscutum not differentiated from scutellum by sulcus, nor visible, nor continuous with mesepisternum.] Hemelytron (Fig. 2) coleopteroid, clavus and corium fused; hinge and a narrow rim of membrane present. Hemelytron obliquely angulate along posterior margin, caudo­lateral angle extending well onto 5th abdominal tergum. Lateral margins of hemelytra nearly straight, carinate, narrowly “clasping” lateral margins of pterothorax (Fig. 21). Hemelytron length 0.62, maximum width 0.32; commissure length 0.32; distance from posterior (distal) margin of hemelytron to apex of abdomen 0.32. [Metanotum well sclerotized, extending caudad of scutellum and strongly inflexed to form a posterior rim. Metathoracic wing much reduced but with large membranous area, width 0.15, length, 0.25. Stridulitrum slender, vein­like, width 0.03, length 0.09, with 21 equal sized teeth in 2–3 staggered rows. [In macropter, as in Fig. 28, the stridulitrum (st) is located at base of wing on the Cu vein, and the other stridulitrum (pss) is located in the post cubital sector, which allows each stridulitrum to be struck by the two plectra of the abdomen (pl) when the wings are at rest. In brachypter, the teeth (t) similar to macropter in arrangement (fig. 28a).] Proepimeron (Fig. 11) lightly constricted. Propleural pore large, nearer to pleural suture than collar sulcus (Fig. 11). Mesepisternum lightly constricted; mesepimeron and metepisternum produced and distinctly carinate below groove that receives margin of hemelytron (Fig. 21). Metathoracic scent gland auricle (Fig. 21) directed caudad, broadened distad into a teardrop shape; apex produced as ledge above scent area. Granulose scent area remote from dorsal margin, covering ventral 2/3 of metepisternum. Metapleural flange separated by shallow sulcus from metepisternum; posterior margin of flange gently concave (Fig. 21). Prosternum (Fig. 11) moderately tumid, relatively short, length 0.26; ventral collar relatively long, length 0.11, delineated by a sulcus continuous with sulcus along dorsal margin of proepisternum; proxyphus sharply pointed. Mesosternum anteriorly depressed, with low mesal carina, posteriorly tumid; mesoxyphus moderately produced, sharply pointed. Metasternum moderately produced, metaxyphus bent inward and blunt. [Metacoxal bridges strong, complete in both sexes. Mesendotergites broad, triangular, sheet­like, attached to narrower mesendosternites.]
Abdomen maximum width 0.62, length 0.77. Terga gently arched, caudal margin of tergum 7 evenly rounded (Figs. 2, 41). [Sutures between sterna 3–4 and 4–5 finely dovetailed; 4–5 suture bent slightly cephalad at level of trichobothria. (In female, sterna 4–5 free, but intersegmental margin bent forward at level of trichobothria.) Spiracle on sternum 5 closer (0.04) to posterior margin of segment than are other spiracles; spiracle 8 evidently absent. Terga 1 and 2 (Fig. 42) relatively wide (0.45), with lateral margins cleft. Plectrum dark, sclerotized, width 0.06, length 0.04; striae fine, 0.9 µ apart. Tergum 3 longer in middle, slightly carinate along posterior margin. Tergal sutures 4–5 and 5–6 dovetailed; sutures curving caudad so that tergum 6 is shorter than tergum 4, 5, or 7. Maximum width of terga 0.50; medial lengths: 1­0.07, 2­0.05, 3­0.04, 4­0.13, 5­0.14, 6­0.09, 7­.17. Scent gland scar widths: 3–4: 0.11, 4–5: 0.10, 5–6: 0.13. Terga 5–7 inflexed and grooved laterad to receive mesal margin of connexivum. Epipleurites 3–6 moderately wide (.03). Connexivum relatively wide, widest across junction of hypopleurites 4 and 5, narrowed cephalad and caudad, hypopleurite widths: 2­0.03, 3­0.05, 4­0.07, 5­0.07, 6­0.06, 7­0.03; lengths: 2­ 0.03, 3­0.13, 4­0.11, 5­0.13, 6­0.19, 7­0.16. Hypopleurite junction 5–6 oblique, others transverse. Tergum 7 and sternum 7 internally lightly impressed laterad for reception of segment 8 and genital capsule. No anterior apodemes visible on sternum 7. Genital capsule (Fig. 53) width 0.19; posterior rim narrowed to small mesal cleft; dorsal opening narrow compared to clasper opening; parandria broad, sharply pointed. Epiproct (Fig. 53) relatively broad, lightly sclerotized; paraprocts narrow; small dorsal and ventral pairs of anal sclerites. Clasper (Figs. 69 & 70) shank short, broad, with a large tooth­like inner projection; blade slender, straight, ecarinate, lateral on shank. Phallus (Fig. 86 & 87) with short gonoporal process of 1 basal coil with membranous sleeve, and 3 slender distal coils; helicoid process ab sent. Sperm reservoir relatively large; wings directed basad; holding sclerites slender. Phallotheca with dorsal surface unsclerotized, venter sclerotized. [In female, terga 1 + 2 sclerotized. Tergum 3 long (0.10), ecarinate. Tergum 8 with caudad margin inflexed, with 2 weak anterior submesal parallel sutures that fade before caudal margin. Tergal suture 6–7 complete (Fig. 49). Hypopleurite (paratergite) 8 evidently lacking a spiracle. Tergum 9 short, c­shaped, nearly fused to epipleurites, with long slender medial anterior apodeme; epipleurite 9 large, with weak anterior apodeme; hypopleurite 9 vertically divided. Valvula length 0.42. Spermatheca (Fig. 73) with hemispherical bulb; sclerotized distal duct elongate, thick; unsclerotized basal duct very short).]
Profemur (Fig. 115) moderately incrassate, length 0.37, width 0.15; convex above and below; armed beneath on distal 1/3 with a prominent sharp spine and a second very small spine immediately distad. Protibia slightly bent, with small tubercles on inner face; distal apex with two short spurs, without a spine; protibial length 0.31, distal width 0.09. Mesotibia with row of 2 short spurs; metatibia with 2 rows of 2 spurs; metatibial length 0.43, medial width 0.05; metatarsomere lengths: I 0.13, II 0.04, III 0.06. Labium reaching between mesocoxae, 1st segment attaining or slightly exceeding base of head; labial segment lengths: I 0.18, II 0.20, III 0.13, IV 0.16. Antennal segments relatively thick; segment 1 terete, 2 clavate, 3 and 4 fusiform; width of 4 0.07; antennal segment lengths: I 0.11, II 0.22, III 0.18, IV 0.20. Total body length 1.50.
Macropterous form (Fig. 1). Membrane hyaline with a large dark brown suffused circular blotch mesally beyond apices of coria. Clavus and adjacent area of corium laterad of claval suture pale yellowish testaceous, usually broadened basally to cover entire basal 1/4 of corium. Corium with extreme base dark chocolate brown, extending caudo­mesad along inner margin of clavus as a tapering elongate triangle to terminate well before apex of scutellum; remainder of corium uniformly dark red­brown. Pronotum with humeral angles prominent, broader than area across calli; lateral pronotal margins strongly sinuate. Hemelytra completely covering abdomen; membrane attaining posterior end of abdomen. Ocelli larger than in brachypter (dia. 0.03). Head length 0.22, width 0.40; interocular space 0.25. Pronotal length 0.38, width anterior lobe 0.58, width across humeri 0.64. Scutellar length 0.22, width 0.33. Hemelytral commissure length 0.25; midline distance from apex of clavus to apex of corium 0.31; midline distance apex corium to apex membrane 0.28. Mesosternum enlarged, prominently tumid and transversely rugulose. Two metathoracic wing stridulitra (as in Fig. 28); one basad of hamus (M) on thickened cubital vein 0.10 long, bearing 13 semicircular teeth in 7 staggered rows of 1–3 teeth, each 6–10 µ wide; other, in membrane of postcubital sector (as in Fig. 28 a), a convex sclerite 0.05 x 0.09 bearing 20 teeth in 6 staggered rows of 2–4 teeth, each 6–10 µ wide. Labium at most attaining mesocoxae; labial segment lengths: I 0.16, II 0.20, III 0.14, IV 0.18. Antennal segment lengths: I 0.15, II 0.26, III 0.22, IV 0.25. Total body length 1.72.
Material Examined. HOLOTYPE: Brachypterous male. SOUTH AFRICA: Cape Province: Cape Point Nature Reserve, 30 I 1968 (J. A. & S. Slater, T. Schuh, M. Sweet). In National Collection of Insects, Pretoria, South Africa.
PARATYPES: 8 m, 9 f B, same data as holotype. 16 m 6 f B, 9 m 13 f M, same locality, 3.XII.1967 (M. H. Sweet no. 98). 3 m 2 f B, same locality, 5.XII.1967 (M. H. Sweet no. 96). 3 f B, same locality, 7.XII.1967 (M. H. Sweet no. 100). 9 m 8 f M, Cape Province: Cape Peninsula, Muizenberg Mt., 1600', 23.X.1967 (M. H. Sweet no. 23). 1 f B, Cape Peninsula Hout Bay, 23.I.1968 (S.S.S.S.). 4 m 2 f B, 1 m M, just N. Outiniqua Pass Summit, S. of Oudtshoorn, 7.II.1968 (S.S.S.S.). 1 m 2 f B, 1 m M, 4 mi. N. Gydo Pass Summit, N. Ceres, 26.I.1968 (S.S.S.S.). 3 m 4 f B, same locality, 3600', 17.X.1967 (M. H. Sweet no. 37). 4 m 15 f B, 13 m 28 f M, 17 mi. N. Ceres, 3250', 17.X.1967 (M. H. Sweet no. 36). 3 m 4 f B, 3 m M, Gydo Pass 9 mi. N. Ceres, 3025', 18.X.1967 (M. H. Sweet no. 38). 7 m B, 18 m 16 f M, Dutoit's Kloof 10 mi. W. Worcester, 875', 23.X.1967 (M. H. Sweet, no. 49). 4 m 4 f B, 1 m 1 f M, Dutoit's Kloof, E. Slope, 1600', 23.X.1967 (M. H. Sweet no. 50). 1 m, 1 f B, 1 m M, 1 mi. N. Swellendam, 500', 15.XI.1967 (M. H. Sweet no. 74). 2 m 1 f B, 5 mi. NE. of Knysna 500', 21.XI.1967 (M. H. Sweet no. 89). 5 m 4 f B, 6 mi. E. Matjesfontein, 20.I. 1968 (S.S.S.S.). 1 m 3 f B, 1 f M, Neuwieskloof Pass 2 mi. S. Tulbagh, 350', 27.I.1967 (S.S.S.S.). 1 m 2 f B, Albertinia 4–5.II.1968 (S.S.S.S.). 1 f B, 1 m 1 f M, Robinson's Pass Summit, 20 mi. N. Mossel Bay, 6.II.1968 (S.S.S.S.). 1 m B, 6 mi. E. Plettenberg Bay, 500', 12–13.II.1968 (S.S.S.S.). 1 m B, 1 m M, 22 mi. W. Grahamstown, 500', 15.II.1968 (S.S.S.S.). Natal, 1 M: Kloof, 1,500', IX. 1926 (R. E. Turner). 1 m M, St. Lucia Estuary 29.IX.1974 (S. Slater and J. Ecker). 1 m 1 f M, 4.6 mi. N. Cato Ridge, 16.IV.1968 (S.S.S.). Transvaal, 1 f M, Zoutpansberg, 4500', 5 mi. N. Louis Trichardt, 8.V.1968 (S.S.S.S.). — 1 f B, 1 m M, Rustenberg Kloof, 4.I.1968 (S.S.S.S.). 1 f B, 2 mi. SW. Rustenberg Kloof 2.X. 1974 (S. Slater). 1 m B, 9 mi. SSW Skukuza Kruger Park, 2.IV.1968 (S.S.S.S.). 1 f B, Long Tom Pass, 6300', 23.IV.1968 (M. H. Sweet no. 236). 1 f B, 6 m 7 f M, Long Tom Pass, 6700' 24.IV.1968 (M. H. Sweet no. 238). 2 m 1 f M, Koster, 10.IX.1968 (J. Munting). 1 m M Johannesburg, The Wilds. 22.1 X. 1974. 1 m 2 f B, same locality, 28.IX.1974 (J. A. Slater) In National Collection of Insects, Pretoria, M.H. Sweet and J.A. Slater Collections.
Etymology. The specific name pulchellus is Latin for beautiful. P. pulchellus, especially the macropterous form (Fig. 1), is unusual in being a bright black, yellow and white insect in contrast with the relatively dull browns and blacks of most other species of Plinthisus.
Variation. The yellowish hemelytral bar in brachypters is variable in degree of development; frequently it is reduced to a small indistinct reddish brown area; occasionally it is completely lacking. In a few brachypters it is broadened basally to broadly attain the lateral margin and encompass nearly the entire basal 1/4 of the hemelytron. Some individuals have the 3rd and 4th antennal segments partially or completely testaceous. The entire pro­ and mesotibiae as well as the distal ends of the femora may be testaceous. Frequently the small spine immediately distad of the large ventral spine on the profemora is absent. In brachypters the hemelytral structure is constant as described above. The observed differences are evidently individual, not population variants because the whole range of differences may be found in a long series from a single location.
Discussion. P. pulchellus appears to be most closely related to P. himyaritus, which Linnavuori (1978) described from three brachypterous specimens from Yemen. These specimens are dark in color, resembling the darkest extreme in the P. pulchellus series. The species may be distinguished (comparing brachypters) as follows: 1) the blade of the clasper (Fig. 71) of P. himyaritus is bent at a greater angle than is that of P. pulchellus (Fig. 69 & 70); 2) the metatibia is proportionally longer in P. himyaritus as compared to hemelytron width (0.47: 0.38) than in P. pulchellus (0.43: 0.40); 3) the length of the commissure is distinctly less than the width of the scutellum in P. himyaritus (0.40: 0.45), while subequal in P. pulchellus (0.32: 0.33); and 4) in P. himyaritus, a row of large punctures in the sulcus separates the metapleural flange from the metepisternum while in P. pulchellus, the flange sulcus is impunctate (Fig. 21). Based on his description of P. himyaritus beniamaricus from Eritrea (Linnavuori 1989), we concur with Linnavuori's suggestion that it is a separate species, and here raise it to species rank: Plinthisus beniamaricus stat. nov.
While a distinct species­group as indicated in the key, we place the Pulchellus group in the subgenus Isioscytus (Wagner 1963) because: 1) the hemelytron of the brachypter is coleopteroid (Fig. 2), with an obliquely angled caudal margin which extends to the fifth abdominal tergum and bears a fringe of membrane; 2) the clasper (Fig. 69) has the blade placed laterad on the shank; 3) there is one row of profemoral spines (Fig. 114); and 4) the body length is under 1.80 mm.
description: Published as part of 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, pp. 1-56 in Zootaxa 533 on pages 13-17, DOI: 10.5281/zenodo.157231