Euschistus (Euschistus) tacitus Bianchi & Grazia, 2017

Bianchi, Filipe Michels, Barão, Kim Ribeiro & Grazia, Jocelia, 2017, Review of the sulcacitus group of Euschistus (Pentatomidae: Pentatominae: Carpocorini) with description of the internal female genitalia and a new species, Zootaxa 4362 (3), pp. 348-358 : 356-357

Euschistus (Euschistus) tacitus Bianchi & Grazia sp. nov.

( Figs 5 , 18–20 , 26 , 39–41 , 57–59 , 64 )

Etymology: Epithet alludes to the external morphological similarities among the species of the sulcacitus group and the new species. From taceo (Latin), to be silent, say nothing; tacitus , meaning implied, unmentioned, in reference to a hidden species.

Distribution: Mexico (Chiapas, Veracruz); Costa Rica (Alajuela).

Type locality: Lacanja , Chiapas, Mexico.

Type material: Holotype: MEXICO: ♂, Chiapas: Near Lacanjah, 310m, 16.77°N 91.13°W, 0 8 Jul 2009, D. Forero & G. Zhang [MEX09_SM_L15] / PTM00283 ( UNAM). Paratypes: COSTA RICA: 1♂ 1♀ Alajuela: On hwy 4S of Mirador, 139m, 10.50°N 84.59°W, 0 9 Dec 2008, Weirauch & Forero [CR 0 8 L12] (1♂ UFRG) / PTM0285 (1♀ UFRG) (abdomen removed) ; 1♂ Guanacaste: 16 km E of La Cruz, Hacienda Los Inocentes , 6.23.0 4, MV+UV light / COLLECTIO NACIONAL MUSEUM Praha, Czech Republic (1♂ NMPC) ; 1♂ Dos Rios, 8.16.0 2 / COLLECTIO NACIONAL MUSEUM Praha, Czech Republic (1♂ NMPC) ; 1♀ Puntarenas: Hacienda Baru near to Dominical, 2.16.0 4 MV + UV light / COLLECTIO NACIONAL MUSEUM Praha, Czech Republic (1♀ MNRJ) ; MEXICO: 1♂, 2♀ Veracruz: Rd between Cuetzalapan and Miguel Hidalgo, 361m, 18.37°N 95.01°W, 0 5 Jul 2009, D. Forero & G. Zhang [ MEX09_SM_L5 ] / PTM00287 (1♀ UFRG) (abdomen removed), PTM00288 (1♀ UFRG) (abdomen removed), PTM00289 (1♂ UCR) ; 1♂ Chiapas: Agua Fria, about 8.5 km off Hwy 186, 23m, 17.74°N 92.08°W, 0 6 Jul 2009, D. Forero & G. Zhang [ MEX09_SM_L7 ] / PTM00286 (1♂ UFRG) (pygophore removed) ; 3♂ 2♀ Near Lacanjah, 310m, 16.77°N 91.13°W, 0 8 Jul 2009, D. Forero & G. Zhang [ MEX09_SM_L15 ] / PTM0284 (1♂ UFRG), (1♂ 1♀ AMNH, 1♂ MNRJ 1♀ UNAM) .

Description: Dorsal surface light brown; punctures black; punctures smaller on hemelytra than on remaining body parts. Humeri acutely projected laterally, but not developed as a spine, varying from light brown to reddish. Ventral surface greenish to light-yellow; punctures concolorous with the surface. Antennae uniformly yellow to orange ( Fig. 5 ).

Head longer than wide; head punctate, punctures less dense on disc. Clypeus rounded apically; clypeus slightly longer than mandibular plates, rarely equal in length. Mandibular plates rounded apically. Rostrum reaching metacoxae. Anterolateral margins of pronotum toothed anteriorly and smooth posteriorly; teeth-like projections small, dark brown. Scutellum reaching abdominal segment V; anterolateral angles foveate. Punctures on scutellum and hemelytra smaller apically than basally. Membrane of hemelytra light brown; exocorium reddish in some specimens. Evaporatorium of metasternal glands not surpassing median line between ostiole and lateral margin of mesopleuron; spout peritreme. Presence of 1+1 dark spots at base of leg between epimeron and episternum of each pleurite, plus 1+1 at metepimeron medially. Legs concolorous with ventral surface of thorax; small dark dots on femora and tibiae.

Abdomen: dorsally, disc of connexivum yellow, black stripes on anterior and posterior margins; ventrally, anterior angle with dark spot. Spiracles concolorous with abdominal sternites.

Male genitalia: Pygophore trapezoidal. Dorsal rim uniformly concave in dorsal view ( Fig. 18 ) median projection of dorsal rim long, sinuosity shallow; superior process of dorsal rim tooth-like. Ventral rim slightly sinuous, convex medially in ventral view ( Fig. 20 ). In posterior view, ventral rim protuberant medially; superior layer of ventral rim excavated in V-shape in posterior view ( Fig. 19 ). Paramere: margin connecting basal and apical process slightly concave; apical process somewhat spatulate at apex; middle process not developed ( Fig. 26 ).

Female genitalia: Posterior margin of gonocoxites VIII concave, posterolateral margin of gonocoxites VIII projected posteriorly, reaching middle of gonocoxites IX. Gonocoxites IX 2 times wider than long, lateral margins strongly rounded; anterior margins of gonocoxites IX straight, posterior margin convex ( Fig. 57 ). Posterior region of ductus receptaculi proximalis straight, not dilated. Ductus receptaculi distalis dilated adjacent to anterior annular flanges. Pars intermedialis sclerotized at basal three-fourths ( Fig. 64 ).

Comments. The external morphology of the sulcacitus group is homogeneous among its species. Some characteristics (e.g. coloration of dorsal and ventral surfaces of body, shape and length of humeral angles, and total body length) vary intraspecifically, making them useless to species diagnosis. Otherwise, the genitalic morphology provides valuable characters to species definition. Euschistus tacitus sp. nov. is more similar to E. sulcacitus than to the others species of the group by the posterior margin of pygophore slightly sinuate, convex mesially; and by the laterotergites IX not surpassing dorsal band that unites laterotergites VIII in posteroventral view. Euschistus tacitus sp. nov. can be distinguished from E. sulcacitus by the inferior layer of ventral rim mesially tumescent in posterior view, and posterior margin of gonocoxites VIII mesially slightly concave.

Figures

FIGURES 1–5. Dorsal view of representative specimens of sulcacitus group species. 1, Euschistus (Euschistus) corcoVacitus; 2, Euschistus (Euschistus) olacitus; 3, Euschistus (Euschistus) palacitus; 4, Euschistus (Euschistus) sulcacitus; 5, Euschistus (Euschistus) tacitus sp. nov., holotype. Scale bars: 2 mm.

FIGURES 6–20. Dissected and macerated pygophore of species of sulcacitus group. Pygophore in dorsal (6, 9, 12, 15, 18), posterior (7, 10, 13, 16, 19), and ventral (8, 11, 14, 17, 20) views. 6–8, Euschistus (Euschistus) corcoVacitus; 9–11, Euschistus (Euschistus) olacitus; 12–14, Euschistus (Euschistus) palacitus; 15–17, Euschistus (Euschistus) sulcacitus; 18–20, Euschistus (Euschistus) tacitus sp. nov.. dr, dorsal rim; mp, median projection; par, paramere; slvr, superior layer of ventral rim; spdr, superior process of dorsal rim; vr, ventral rim. Scale bars: 0.25 mm.

FIGURES 21–26. Right paramere of species of sulcacitus group. 21, schematic drawing of paramere indicating its regionalization; 22, Euschistus (Euschistus) corcoVacitus; 23, Euschistus (Euschistus) olacitus; 24, Euschistus (Euschistus) palacitus; 25, Euschistus (Euschistus) sulcacitus; 26, Euschistus (Euschistus) tacitus sp. nov. app, apical process of paramere; bpp, basal process of paramere; cr, crown; st, stem. Scale bars: 0.25 mm.

FIGURES 27–41. Phallus of species of sulcacitus group. Phallus in dorsal (27, 30, 33, 36, 39), ventral (28, 31, 34, 37, 40) and lateral (29, 32, 35, 38, 41) views. 27–29, Euschistus (Euschistus) corcoVacitus; 30–32, Euschistus (Euschistus) olacitus; 33–35, Euschistus (Euschistus) palacitus; 36–38, Euschistus (Euschistus) sulcacitus; 39–41, Euschistus (Euschistus) tacitus sp. nov. Scale bars: 0.25 mm.

FIGURES 45–59. Female genital plates of species of sulcacitus group. Genital plates in posterior (45, 48, 51, 54, 57) and postero-ventral (45, 46, 49, 50, 52, 53, 55, 56, 58, 59) views. 45–47, Euschistus (Euschistus) corcoVacitus; 48–50, Euschistus (Euschistus) olacitus; 51–53, Euschistus (Euschistus) palacitus; 54–56, Euschistus (Euschistus) sulcacitus; 57–59, Euschistus (Euschistus) tacitus sp. nov.. gc, gonocoxites; la, laterotergites. Scale bars: 1 mm.

FIGURES 60–64. Female internal genitalia of species of sulcacitus group. 60, Euschistus (Euschistus) corcoVacitus; 61, Euschistus (Euschistus) olacitus; 62, Euschistus (Euschistus) palacitus; 63, Euschistus (Euschistus) sulcacitus; 64, Euschistus (Euschistus) tacitus sp. nov.. Insets are the capsula seminalis. aaf, anterior anular flange; cs, capsula seminalis; dr, ductus receptaculi; g, gonapophysis; gc, gonocoxites; la, laterotergites; paf, posterior anular flange; pi, pars intermedialis; rs, ring sclerites; tvi, thickening of vaginal intima; va, vesicular area. Scale bars: 0.5 mm.