Thyanta (Argosoma) obtusa, Rider, D. A. & Chapin, J. B., 1991

Rider, D. A. & Chapin, J. B., 1991, Revision Of The Genus Thyanta Stal, 1862 (Heteroptera: Pentatomidae) I. South America, J. New York Entomol. Soc. 99, No. 1, pp. 1-77 : 62-64

Thyanta (Argosoma) obtusa Rider, new species Fig. 308-321, Map 3

Description. Small to medium; dorsal surface pale green to testaceous, lacking all red and black markings; punctures usually concolorous with surface.

Apex of head arcuately rounded; outer jugal margins subparallel for middle third of distance from eyes to apex ( Fig. 309). Antennae pale brown, apical 3 segments sometimes reddish-brown. Anterolateral margins of pronotum straight to slightly concave in dorsal view; humeral angles rounded, protruding only slightly beyond base of adjacent coria ( Fig. 308); pronotal cicatrices immaculate. Hemelytra shallowly and uniformly punctured; posterior margins slightly convex; costal angles narrowly rounded, reaching beyond middle of penultimate connexival segments; hemelytral membranes hyaline, usually with a few vague brown flecks distally. Connexiva narrowly exposed; incisures sometimes minutely marked with black.

Ventral surface yellowish-green to brown; punctures usually concolorous with surface. Rostrum pale green to brown, apical half of segment 4 black; usually reaching onto third (second visible) abdominal segment. Femora and tibiae green to brown, sometimes tarsal segments darker. Ostiolar canals acuminate apically. Postspiracular black spots absent; posterolateral angles of abdominal sternites usually immaculate, extreme tip sometimes black.

Mesial margins ofbasal plates nearly straight; posterior margins sinuous; posteromesial angles rounded. Sclerotized rod slightly swollen subapically, narrowed apically ( Fig. 320); spermathecal duct below proximal flange with only slight amount of swelling or coiling ( Fig. 321). Posterior margin of pygophore shallowly and broadly U-shaped, medial portion straight to slightly convex in caudal view ( Fig. 316); posterolateral angles prominent in ventral and lateral views ( Figs. 31 7, 319); blunt, chinlike protuberance on posteroventral surface relatively small, not visible in dorsal view ( Fig. 318). Each paramere in ectal view relatively robust, apex obtuse ( Fig. 312); in medial view apex rounded, curving only slightly dorsad, concave surface oriented more dorsad than mediad ( Fig. 310); distinct obtuse protuberance on shaft; roughened, spiculate area on lateral surface circular or triangular ( Fig. 311). Each lateral conjunctiva! lobe of aedeagus with 1-2 nonsclerotized diverticula ( Fig. 315); dorsomedial lobe apparently lacking ( Fig. 314); penisfilum and median penial lobes nearly obscured by conjunctiva! membrane ( Fig. 313).

Measurements. Total length 6.86-7.73 (6.86); total width 4.42-5.20 (4.42); medial length ofpronotum 1.36-1.62 (1.47). Medial length ofscutellum 2.96-3.15 (2.98); basal width 2.80-3.09 (2.83); width at distal end of frena 1.03-1.10 (1.03). Length ofhead 1.46-1.59 (1.46); width 1.92-2.13 (l.92). Length of segments 1 -5 ofantennae 0.37-0.42 (0.37), 0.70-0.92 (0.70), 0.83-1.03 (0.92), 1.05-1.20 (1.05), and 1.03-1.18 (1.03), respectively. Length of segments 2-4 of rostrum 1.12-1.23 (1.12), 0.68-0.79 (0.68), and 0. 72-0.77 (0. 72), respectively.

Holotype. 縠 labeled (a) " Villa Vieja Colombia 1 l-IV-45" (b) " Thyanta nitidula Ruckes det. H. Ruckes." Deposited in the California Academy of Sciences (San Francisco) .

Paratypes. 455, 1 ~. " Magdalena, Colom. ll 0 l 0'N, 76°08'W Apr. 1973, 800 MM. Madison, Coll." (255 LHR); (a) " Trujillo Trujillo, Yenz . 12-VII- 1964 " (b) " E. Osuna M. Gelbes " (c) "Venezuela-Inst. Zool. Agricola-Fae, Agronomia Univ. Central" (c3 IZA) ; (a) " El Limon Ar. VENEZUELA 450m. 30-V-65 " (b) " F. Fernandez Y. Col. " (c) "Venezuela-Inst. Zool. Agricola-Fae, Agronomia Univ. Central" (5 IZA) ; and (a) " Turmero ; AR Venezuela 466 m 22.V.53 " (b) "col. J. Requena " (c) "Venezuela-Inst Zool.Agricola-Fac.Agronomia Univ. Central" (~ IZA) .

Distribution. Northern South America ( Map 3).

Comments. This species is related to T. sinuata and T. xerotica , but can be recognized by the structure of the male genitalia. Thyanta obtusa has the posterior margin of the pygophore broadly U-shaped in caudal view, while in T. sinuata it is broadly V-shaped. Thyanta obtusa can be separated from T. xerotica by the obtuse protuberance on the shaft of each paramere, which is reduced or absent in T. xerotica. Etymology. Named for the obtuse apex of each paramere when viewed medially.