Psorus Bergroth, 1914

Fernandes, José Antônio M., Grazia, Jocelia & Lobo, Deise S., 2008, Revision of the genus Psorus Bergroth, 1914 (Hemiptera: Pentatomidae: Discocephalinae), Zootaxa 1696, pp. 48-56 : 48-50

Psorus Bergroth, 1914

Psorus Bergroth, 1914: 423–425; Rolston, 1981: 41

Type species: Psorus cassidiformis Bergroth, 1914 by monotypy.

Etymology: psorus = freckled

Description. Body of medium size (10.0–15.0); broadly oval, mildly convex above and beneath; surface hispid with short, fine, suberect stiff hairs arising between fine, somewhat dense dark brown punctures, giving a velvet aspect to dorsum. Dorsal and ventral surfaces variegated in yellow and brown. General color castaneous to ochraceous with dark brown to ferrugineous punctures, irregularly distributed or forming patches on posterior half of pronotum, scutellum and corium. Head slightly longer than median length of pronotum, feebly declivous, provided with anteocular, spatulate lobes exceeding width through eyes and preceded by a deep sinus; antelobular margins somewhat explanate and reflexed; juga elevated into crest centrally above apex of tylus; eyes large, vertically elliptical in lateral aspect, substylate, and elevated above surrounding disc; interocellar distance three times distance from ocellus to eye. Antennae five-segmented, pubescent, reaching nearly to middle of scutellum; segment I not attaining apex of head, II shorter than I, almost half as long as III, IV, and V; V fusiform. Antenniferous tubercles not visible from above. Antennal segments mostly castaneous with yellowish rings or macula: segment I with a median macula; II with basal and apical rings; III with median and apical rings; IV with broad median ring; segment V with basal and apical rings; in some specimensegments I–III reddish. Bucculae arising anteriorly opposite antenniferous tubercles, moderately elevated posteriorly, parallel; buccular canal wide and deep. Rostrum reaching metacoxae; segment I short, not exceeding the anterior margin of prosternum: II shorter than III and IV combined. Pronotum about three times as wide as long medially, subreniform in outline, lateral portions explanate, their margins arcuate; anterior apical angles reaching, at least, anterior margins of eyes and there provided with a small, acute lobe separated from margin by a deep narrow notch; surface slightly convex, with broad shallow transverse groove across middle of disc. Humeri weakly tumid, emarginate; posterior margin almost straight, posterior angles obsolescent. With small tumescence laterad. Scutellum long, nearly reaching apex of body, about one-half again as long as wide at base; frenum not reaching middle of scutellar lateral margins; base convex, with three tubercules; another prominent, median, obtuse tubercle present at about the base of post frenal lobe; apex obtusely emarginate or almost truncate, anteapical margins very feebly reflexed.

Hemelytra. Almost as long as scutellum; costal margins reflexed near the base, than obtusely angulated at the third abdominal segment; membrane short and narrowly visible beneath scutellum; apex of membrane rectilinear in males and rounded in females. Veins darker than membrane forming, at least, two basal cells with 7 or 8 longitudinal veins, sometimes bifurcate at apex.

Prosternum broadly and deeply sulcate; mesosternum tumid, impunctate, broadly and shallowly sulcate, posterior margins shallowly notched centrally; metasternum flat, hexagonal, margins distinctly elevated into thin carina-like edges. Metapleural evaporatorium occupying most of the sclerite; ostiolar peritrema lanceolate reaching the end of evaporatorium area.

Legs. Procoxae apart from mesocoxae; metacoxae closer to mesocoxae than to each other; tibiae hemicylindric, broadly sulcate above. Femora with a preapical dark castaneous macula; femora and tibiae covered with castaneous dots. Abdomen shallowly and broadly furrowed to fifth sternite. Each connexival segment with transverse dark castaneous macula near anterior margin; posterolateral angles not developed. Spiracles more than twice as far from lateral abdominal margin as from anterior margin of segment. Trichobothria lateral to an imaginary longitudinal line connecting spiracles. Ventral surface dark castaneous, rarely punctured, sometimes with yellow areas on propleura and along lateral third of abdomen. Male: Pygophore opening widely posteriorly, posterolateral angles projecting backward. Pygophore excavated on each side of proctiger and along inner wall of posterolateral angles. Ventral rim elevated, with median excavation in “U” shape, expanded laterad toward apex of posterolateral angles of pygophore. Long pubescence covering ventral surface of posterolateral angles of pygophore; short pubescence covering ventral wall of pygophore and proctiger. Proctiger (segment X) cylindrical, open posteriorly, well developed, and obscuring parameres in dorsal view; ventral wall expanded posteriorly into a process. Phallus: Basal plates of articulatory apparatus as wide as phallotheca; processus capitati delicate, moderate in size; phallotheca strongly sclerotized, inflated laterad and ventrad, pyriform in dorsal and ventral views; conjunctiva absent; vesica tubular, strongly reduced in size relative to phallotheca. Female: Posterior border of urosternite VII with semielyptical arc, apical angles virtually as long as laterotergites 8. Gonocoxites 8 well developed and obscuring gonocoxites 9, lateral margins folded with median margins of laterotergites 8; surface of gonocoxites 8 with many obliquely disposed sulci. Laterotergites 8 shorter than laterotergites 9; spiracles at basal angles. Posterior margins of laterotergites 9 rounded, forming together a semicircle; median margins strongly excavated, embracing laterally segment X. Gonapophyses 9 and thickenings of vaginal intima heavily sclerotized and projecting in a spear tip-like structure. Chitinnelipsen present. Ectodermal genital ducts: orificium receptaculi opening at apex of the spear tiplike projection. Ductus receptaculi dilated before anterior flange; pars intermedialis with basal half dilated. Capsula seminalis semiglobose, with three fingerlike processes.

Distribution (Fig. 15). Trinidad; French Guyana; Brazil: Amapá, Pará, Amazonas; Peru: Madre de Dios.

Comments. Psorus is allied to a few genera of Discocephalini that have a long scutellum, the body somewhat depressed, the dorsal surface variegate, color castaneous to ochraceous with dark brown to ferruginous punctures which are irregularly distributed or form patches, tubercles on the scutellum, the metasternum broadly hexagonal causing the metacoxae to be placed closer to the corresponding mesocoxae than to each other. These genera are Coriplatus White, Abascantus Stål , and Pelidnocoris Stål (Stål 1867, 1872, Ruckes 1966a, Ruckes & Becker 1970, Becker 1977). Psorus can be distinguished from these by its short rostrum, the entire anterolateral margins of pronotum, and the presence of laterotergites 9. Three other genera – Alcippus Stål, Paralcippus Becker & Grazia, and Eurystethus Mayr—can also be compared to the genera above ( Ruckes 1966b, Becker & Grazia 1986, 1989); but the latter three have a short scutellum and their laterotergites 9 are also present. Psorus can be distinguished from them by the anterolateral margins of pronotum clearly surpassing the level of eyes; and by scutellum being long and having tubercles distinct in number, position, and size. Psorus shares with Eurystethus the well developed and tube-like proctiger (segment X) with the anal orifice opening posteriorly.