Argosoma Rider

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 : 75-77

Subgenus Argosoma Rider

Thyanta (Argosoma) Rider [in Rider and Chapin, 199 l:33].

Type species. Pentatoma patruelis Stal, 1859 (by original designation, Rider and Chapin, 1991).

Diagnosis. Punctation coarse, sparse, dorsal surface appearing glossy. Anterolateral margins of pronotum straight to slightly concave, concolorous with surface of pronotum; humeral angles rounded to angulate, rarely spinose; pronotal cicatrices usually immaculate, sometimes faintly marked with fuscous in mesial angles. Posterior termination of each buccula evanescent.

Distal end ofsclerotized rod with or without subapical swelling, never cone-shaped; spermathecal bulb globose; spermathecal duct below proximal flange slightly to greatly swollen and coiled, but never forming distinct cylindrical structure. Pygophoral opening relatively large; posterior margin usually broadly and shallowly U-shaped; posteroventral surface ofpygophore produced into blunt chin-like protuberance. Each paramere acute to narrowly rounded apically, obtuse protuberance on shaft moderate in size to absent, possessing distinct dorsomedial concave surface; roughened, spiculate area on lateral surface ofparamere usually circular, rarely linear ( T. boliviensis Rider ). Theca reniform, lacking dorsolateral protuberances; each lateral conjuctival lobe usually with single diverticulum; median penial lobes and penisfilum usually relatively small.

Comments. This is the largest subgenus, containing 20 species, and the included species are also the most difficult to identify. It is often necessary to examine the male genitalia in order to make accurate determinations. Within geographical areas, the internal female genitalia are usually distinctive.

This subgenus can be divided into two groups based primarily on the structure of the spermatheca. In T. boliviensis, T. brasiliensis Jensen-Haarup , T. emarginata Rider , and T. hamulata Rider , the sclerotized rod is somewhat elongate and lacks any subapical swelling. The remaining species have the sclerotized rod shorter and distinctly swollen subapically, becoming narrowed apically.