Thyanta (Argosoma) acuminata Ruckes

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 : 39-41

Thyanta (Argosoma) acuminata Ruckes

Figs. 199-214, Map 2

Thyanta acuminata Ruckes, 1956:63-65 , fig. 5.

Diagnosis. Small to medium; dorsal surface green to brown, sometimes with reddish markings on dorsal surface of pronotum and head; punctures usually concolorous with surface.

Apex of head evenly rounded; outer jugal margins subparallel for middle third of distance from eyes to apex ( Fig. 200). Anterolateral margins of pronotum straight to slightly concave in dorsal view; humeral angles rounded, protruding only slightly beyond base of adjacent coria ( Fig. 199); pronotal cicatrices immaculate. Hemelytral membranes hyaline, lacking brown distal flecks. Posterolateral angles of connexival segments usually immaculate, sometimes minutely marked with black. Ventral surface green to brown; posterolateral angles ofabdominal stemites immaculate; postspiracular black spots absent. Ostiolar rugae acuminate apically.

Mesial margins ofbasal plates in caudoventral view convex, separated basally and distally; posterior margins convex; posteromesial angles broadly rounded ( Fig. 211). Sclerotized rod relatively short, swollen subapically, gradually narrowing apically ( Fig. 212). Swelling of spermathecal duct below proximal flange shorter than spermathecal pump and narrowing rather abruptly ( Fig. 213). Posterior margin of pygophore in caudal view broadly and shallowly U-shaped, medial portion nearly straight ( Fig. 207); posterolateral angles ofpygophore prominent in both ventral and dorsal views ( Figs. 208, 209); pygophore sinuous in lateral view ( Fig. 210). Apex of each paramere in medial view narrowly rounded to spinose, curving gently dorsad ( Fig. 201); concave surface oriented more dorsad than mediad; roughened, spiculate area on lateral surface oval ( Fig. 202); possessing a distinct spinose lateral lobe in ectal view ( Fig. 203). Aedeagus relatively small; each lateral conjunctiva! lobe with spinose diverticulum apically; median penial lobes spatulate; penisfilum relatively small, short ( Figs. 204-206).

Types. Ruckes (1956) described this species from 1355 and 4~~, all from Argentina and Paraguay. The holotype, which is conserved in the American Museum ofNatural History (New York), was examined.

Distribution. Southern South America ( Map 2).

Specimens examined. 197 specimens collected during every month of the year except July and September; deposited in: AMNH, BMNH, CAS, CU, DAR, EGER, ENGL, FSCA, LHR, MRB, SMEK, IML, UCS, UNL, USNM, ZMB. BOLIVIA: Mataral, V. Grande ; Villa Vicencio . Chuquisaca: Monteagudo . La Paz: Iquisivi . Santa Cruz: Buena Vista , Prov. Ichilo ; Colpa pump stn ., 9 mW Warnes ; Ingenio La Belgica , 38 km N Santa Cruz ; 10 mi W Portachuelo ; Rio Grande pump stn . , 35 m S Santa Cruz ; Saavedra Res. Stn . Tarija: Ing. Bermejo ; Villa Montes . BRAZIL: Minas Gerais: Carmo do R. Claro . PARAGUAY: Central: nr. Nemby . Chaco: Copagro, trans. Chaco km 589 ; Expt. Stn Fem. Col . Concepcion: Horqueta . Guaira: Villarrica . Nueva Asuncion . · Parq. Nae. Tte. Enciso . Presidente Hayes: 42 km NW Benjamin Aceval ; Gran Chaco . ARGENTINA: Laguna de Malvinas . Catamarca: Andalgala ; Belen ; Frias . Chaco: Colonia Benitez ; Fortana ; Labo Montevideo ; Resistencia ; Roque Saenz Peil.a . Cordoba: Alta Garcia ; Guanaco Muerto . Formosa: Clorinda ; 40 km SW Clorinda ; Gran Guardia ; La Florencia Este ; 5 km N Pirane ; 14 km SE Pirane . Jujuy: Perico . La Rioja: La Rioja ; Patquia . Salta: Guemes ; J N Gonzales ; Tartagal ; Rosario de la Frontera ; Urundel . Santa Fe: Carcaraiia . Santiago de! Estero: Chaco, Rio Salada . Tucuman: Cardinal ; El Bachi ; La Aguadita ; 11 km E de Las Cejas ; San Miguel de Tucuman ; Siambón Siambón ..

Comments. This species can be separated from most other congeners by the reduction of nearly all black markings and by the lack ofbrown flecks in the hemelytral membranes. The acute lateral lobe of the parameres is a character this species shares only with T. hamulata . In T. hamulata the apex of each paramere curves dorsad and caudad forming a distinct hook, while in T. acuminata the apex of each paramere curves gently dorsad but does not form a hook. Also, the lateral lobe of the paramere in T. hamulata is triangular, while in T. acuminata it is digitiform and spinose apically.

Female specimens of T. acuminata can be distinguished from the other 3 species of this subgenus which occur in southern South America by examining the spermatheca. Thyanta boliviensis and T. brasiliensis both have the sclerotized rod not at all swollen subapically; both T. acuminata and T. patruelis have this structure swollen subapically, although somewhat less so in T. acuminata . The swelling of the spermathecal duct below the proximal flange is much more extensive in T. patruelis, the length of the swelling being equal to or longer than the spermathecal pump. Also this swelling usually narrows gradually, giving the whole swollen portion the appearance of an inverted cone. In T. acuminata, this swollen portion is much shorter and narrows rather abruptly.