Thyanta Stal

Subgenus Thyanta Stal

Diagnosis. Punctures minute, dense. Posterior termination ofbucculae evanescent. Anterolateral pronotal margins straight to concave, sometimes marked with piceous; each humeral angle rounded to angulate, often spinose; pronotal cicatrices sometimes marked with piceous in mesial angles. Ostiolar canals acuminate apically. Superior surface of each tibia sulcate.

Posterior margins of basal plates sinuous, posteromesial angles entire ( Fig. 13). Distal end of sclerotized rod cone-shaped ( Fig. 14); spermathecal bulb digitiform; cylindrical structure present below proximal flange ( Fig. 15).

Pygophoral opening small, subtended on posteroventral surface by a rectangular or semicircular impression; posterior margin of pygophore straight to concave in caudal view, with medially incised protuberance in middle ( Fig. 9). Each paramere F-shaped, obtuse protuberance on shaft usually prominent, apex spinose, ectal surface convex ( Fig. 3), roughened spiculate area on lateral surface linear ( Fig. 4). Each lateral conjunctival lobe of aedeagus with single spinose diverticulum ( Fig. 6); dorsomedial conjunctiva} lobe usually well-developed ( Fig. 7); theca large, subtriangular in lateral view, with dorsolateral protuberance on each side near caudal limit ( Fig. 8); medial penial lobes and penisfilum moderate in size.

Comments. Species of the subgenus Thyanta have the pygophoral opening subtended by a semicircular or rectangular impression, and the posterior margin is distinctly emarginate medially. Species of Phacidium have the posteroventral surface of the pygophore arcuately rounded or sulcate, and the posterior margin not emarginate medially. The posteroventral surface of the pygophore in species of Argosoma is produced into a blunt chin-like protuberance. Also, species of Argosoma have the ectal surface of each paramere concave, while it is convex in both Phacidium and Thyanta .

The female genitalia are also useful in separating species of Thyanta and Phacidium . In Thyanta the distal end of the sclerotized rod is cone-shaped, and the spermathecal bulb is digitiform. In Phacidium the distal end of the sclerotized rod is swollen subapically and narrowed distally, and the spermathecal bulb is globose. The female genitalia of both Phacidium and Argosoma are very similar, but females can usually be separated by the relative density of the dorsal punctation. The dorsal punctation is relatively dense in Phacidium , while it is less dense and more coarse in Argosoma .