Thyanta (Argosoma) planifrons Ruckes

Rider, David A. & Chapin, J. B., 1992, Revision of the genus Thyanta Stal, 1862 (Heteroptera: Pentatomidae) II. North America, Central America, and the West Indies., Journal N Y Ent Soc 100 (1), No. 1, pp. 42-98 : 77-80

Thyanta (Argosoma) planifrons Ruckes

Figs. 122- 137, Map 6

Thyantaplanifrons Ruckes, 1956:59-61, fig. 3; Rolston and McDonald, 1984:fig. 33. Thyanta casta (of authors, not Stal): Uhler, 1894a:23 l (part); Van Duzee, 1904:52, 54 (part); Kirkaldy, 1909:94 (part); Banks, 1910:90; Van Duzee, 1917:53 (part); Van Duzee, 1923:127- 128; Torre-Bueno, 1939: 231 (part); Froeschner, 1988: 593 (part).

Diagnosis. Vertex ofhead relatively flat; lateraljugal margins subparallel for middle third of distance from eyes to apex ( Fig. 123). Anterolateral margins of pronotum straight to slightly concave in dorsal view; humeral angles rounded, not or only slightly produced beyond base of adjacent corium ( Fig. 122). Pronotal cicatrices immaculate. Rarely with reddish markings on pronotum. Ostiolar canal widening towards apex, wider distally than in middle ( Fig. 137). Abdominal sternites lacking black markings, rarely extreme tip of posterolateral angles of abdominal sternites piceous.

Basal plates with mesial margins slightly convex in caudoventral view, separated basally; posterior margins slightly convex; posteromesial angles rounded to slightly emarginate ( Fig. 134). Sclerotized rod slightly swollen subapically, narrowed apically ( Fig. 135); spermathecal duct only slightly swollen below proximal flange ( Fig. 136). Posterior margin of pygophore broadly and shallowly U-shaped in caudal view, slightly sinuous medially ( Fig. 130); posterior margin weakly concave in ventral and dorsal views ( Figs. 131, 132); posteroventral surface deeply emarginate in lateral view ( Fig. 133). Apex of each paramere nearly acute from both medial and ectal views ( Figs. 124, 125); concave surface oriented more dorsad than mediad; roughened spiculate area on lateral surface elongate-circular ( Fig. 126). Each lateral conjunctiva! lobe of aedeagus with 1 or 2 non-sclerotized diverticula ( Fig. 129); dorsomedial lobe apparently absent ( Fig. 128); median penial lobes spatulate ( Fig. 127).

Types. Ruckes ( I 956) described T. planifrons from 655 and 722 specimens. The holotype, which is from 10 miles west of Alamos, Sonora, Mexico, and all 12 paratypes were examined. The holotype is housed in the American Museum of Natural History (New York).

Distribution. Southwestern U.S. and northwestern Mexico ( Map 6).

Specimens examined. 535 specimens collected during every month except February; deposited in AMNH, ASUT, CAS, DAR, DBT, EGER, FSCA, LACM, LHR, MSU, TAMU, UAT, UCB, UCR, UIM, UMC, UNAM, USNM. UNITED STATES: Arizona: Cochise: Portal ; 5 mi W Portal , SWRS. Pima: Baboquivari Mountains , Browns Canyon ; Organ Pipe Cactus Natl Monument . Santa Cruz: Madera Canyon . California: Imperial . Riverside: Bautista Canyon ; Deep Canyon ; Palm Springs . San Diego: Borego Valley .

MEXICO: Canipole ; 10 mi SW Canipole ; Carmen Island , Porto Ballandra ; Puntbunda. Baja California Norte: Bahia de los Angeles ; Cataviiia ; 10 mi S Cataviiia ; 8 km N Punta Prieta ; 15 mi N Punta Prieta ; San Felipe ; 12 mi S San Felipe ; 15 mi S San Felipe ; San Fernando . Baja California Sur: Bahia Concepcion ; Cabo San Lucas ; 3 mi W Caduaiio ; Comondu ; 10 mi SW Comondu ; 20 mi N Comondu ; 23 mi S Comondu ; 14 mi S El Arco Mine ; 28 mi S El Arco Mine ; 6.5 mi S, 1 mi E El Pescadero ; 15 mi N El Rufugio ; El Sargento ; El Triunfo ; 2 mi NW El Triunfo ; 6 mi N El Triunfo ; Escondido Bay ; 3 mi N Guajademi ; Hamilton Ranch ; 1 km SW Huatamote ; Isla Annelvo ; Isla Catalan ; Isla Cerralvo ; Isla Espirita Santo ; La Paz ; 2 mi S La Paz ; 5 mi SW La Paz ; 7 mi SW La Paz ; 13 mi W La Paz ; 14 mi W La Paz ; 15 mi W La Paz ; 20 mi NW La Paz ; 21 mi W La Paz ; 23 km W La Paz ; 25 mi W La Paz ; 26 mi W La Paz ; 33.5 km NW La Paz ; La Purisima ; Las Animas ; Las Barracas ; Las Tinajitas ; 2 mi SE Las Virgenes ; l mi E Migriiio ; Miraflores ; 5 mi S Miraflores ; 4 mi S Mission San Javier ; Mulege ; 1 mi S Mulege ; 2 mi S Rancho de la Ventana ; 2.6 mi E San Antonio ; 3 mi SW San Antonio ; 5 mi S San Antonio ; 5 mi W San Bartolo ; San Domingo ; 15 mi S San Domingo ; 15 mi N San Ignacio ; 27 mi W San Ignacio ; San Jose del Cabo ; 2 km W San Jose del Cabo ; 10 mi SW San Jose del Cabo ; 1.3 mi N San Jose Viejo ; 3 mi N San Jose Viejo ; 5 mi S San Miguel ; 3 km S, 1.3 km E San Pedro ; 3.5 mi NE San Pedro ; San Sebastian ; 5 mi SE Santa Rosalia ; 12 mi S Santa Rosalia ; Santiago ; 6 mi SW Santiago ; Sierra de la Laguna ; Todos Santos ; 4 mi N Todos Santos ; 28-29 km N Todos Santos ; Venancio ; 30 mi EV. lnsurgentes . Sinaloa: Mazatlan ; 34 mi N Mazatlan . Sonora: 10 mi W Alamos ; Bahia de los San Carlos ; Bahia Kino ; 20 mi NNE Ciudad Obregon ; El Desemboque ; Guaymas , Punta San Antonio ; Hermosillo ; La Choya ; Minas Nuevas ; 15 km S Navojoa ; 15 mi N Navojoa ; San Bernardino , Rio Mayo ; 20 mi S Sonoyta ; Tecoripa ; Tiburon Island ; Yavaros .

Comments. Thyanta planifrons can be separated from all other congeners by the distal widening of the ostiolar canal. Also, the vertex of the head is relatively flat, a character for which this species was named.

The widening of the ostiolar canal is unusual, but not unique. It also occurs in Tepajugosa Van Duzee, a species with essentially the same distribution as Thyanta planifrons . The biological significance of this condition is not known, but would make an interesting study. This is the first record of this species from the United States.