Thyanta (Argosoma) vadosa Rider

Thyanta (Argosoma) vadosa Rider

Figs. 153-167

Thyanta (Argosoma) vadosa Rider [in Rider and Chapin, 1991:55].

Diagnosis. Ovate; dorsal surface green to pale brown; some interstitial areas of pronotum, scutellum, and elytra pale yellow; sometimes marked with reddish-purple between humeral angles, on apex of scutellum, and on tylus and vertex of head. Punctures green to pale brown.

Apex of head arcuately rounded; lateral jugal margins sinuous, subparallel for middle third of distance from eyes to apex ( Fig. 154); vertex convex. Anterolateral margins of pronotum in dorsal view straight to slightly concave; humeral angles rounded to angulate, often projecting beyond base of adjacent corium ( Fig. 153). Pronotal cicatrices immaculate. Punctation becoming sparse medially, central portion of pronotal disc subcalloused. Posterior third of pronotum often darker than rest of pronotum. Posterolateral angles of connexival segments piceous. Ostiolar canals acuminate apically. Postspiracular black spots usually absent (except in brown form); posterolateral angles of abdominal stemites piceous, sometimes only minutely so.

Mesial margins of basal plates straight to slightly convex in caudoventral view; posterior margins slightly convex; posteromesial angles broadly and shallowly emarginate, lateral sides of concavity resulting from excavations in basal plates divergent, not parallel ( Fig. 165). Distal end of sclerotized rod swollen subapically, narrowed apically ( Fig. 166); spermathecal duct moderately swollen and coiled below proximal flange ( Fig. 167). Posterior margin of pygophore in caudal view broadly U-shaped, medial portion straight to slightly convex ( Fig. 161); chin-like protuberance appearing relatively narrow in ventral and dorsal views ( Figs. 162, 163); pygophore deeply emarginate in lateral view ( Fig. 164). Each paramere with concave surface oriented mediad; from ectal view, parameral apex anglinggently mesad ( Fig. 156); from medial view, apex acutely angulate, straight or bending slightly ventrad ( Fig. 15 5); roughened spiculate area on lateral surface circular ( Fig. 157). Each lateral conjunctiva! lobe of aedeagus without sclerotized diverticula ( Fig. 160); dorsomedial conjunctiva! lobe weakly developed ( Fig. 159); median penial lobes spatulate ( Fig. 158).

Types. Rider [in Rider and Chapin, 1991] described T. vadosa from 555 and 5'i''i' female specimens. The holotype 5 was examined and is deposited in the Canadian National Collection, Ottawa, Canada.

Distribution. Trinidad and Tobago; Venezuela.

Specimens examined. 9 specimens collected in January, February, March, May, July, September, and October, deposited in AMNH, ARH, CNC, USNM. BRITISH WEST INDIES: Tobago . Trinidad: Bejucal ; Curepe , Santa Margarita Circular Road ; Saint Augustine ; Santa Margarita Hill .

Comments. In general appearance this is a typical species of the maculata group. The shape of the emargination in the posteromesial angle of each basal plate of the female is distinctive. Thyanta emarginata and T. excavata both have the posteromesial angles of the basal plates deeply emarginate, but the sides of the resulting concavity are nearly parallel, not divergent as in T. vadosa. The male genitalia are also distinctive. Thyanta vadosa is the only species with the apex of each paramere not only acutely angulate (almost acuminate) but also straight or bending slightly ventrad. In the maculata group, all other species having the apex of each paramere acute to acuminate also have the apex bending dorsad.