Belostoma zecai Stefanello, 2024

Stefanello, Fabiano & Azevêdo, Carlos Augusto Silva De, 2024, New species and new records of Belostoma Latreille, 1807 (Insecta: Hemiptera: Belostomatidae) from northeastern Brazil, Zootaxa 5497 (4), pp. 591-600 : 592-594

Belostoma zecai Stefanello , new species

( Figs. 1–2 )

Description. Male, HOLOTYPE, body length 30.80; maximum width 13.10. Paratype male (n = 1), body length 31.80; maximum width 14.10. General shape elliptical, widest at mid-length of hemelytra; overall dorsal coloration brown, with middle part of pronotum and scutellum light-brown. Ventral surface brown ( Fig. 1A–B ).

Head. Eyes triangular, lateral margin almost straight ( Fig. 1C ). Interocular space wide 1.65× width of an eye, interocular space 2.60, eye 1.55; anteoculus 1.2× interoculus, anteoculus 1.95, interoculus 1.65 ( Fig. 1C ). Vertex without median carina. Maxillary plate with dorsal and ventral ends straight, not projected forward, covered with golden setae. Lorogenal cleft without conspicuous fovea. Antenna four-articulated, with lateral projections well-developed. Labium long, four-articulated; article II 0.76× length of III, II 2.15, III 2.80 ( Fig. 1D ).

Thorax. Pronotum without median carina; a pair of depressed rounded areas on disc at anterior half; transverse sulcus setting off band on posterior third; finely rugose, mainly on posterior third behind transverse sulcus; anterior margin concave medially; lateral margin straight; posterolateral corner right-angled; lateral fold of the pronotum not extending up to posterior part; posterior margin straight, slightly angulated laterally; maximum width 2.0× length at midline, maximum width 9.05 (across posterolateral corners), length at midline 4.55 ( Fig. 1C ). Prosternal keel well-developed, projected forward, with apex rounded ( Fig. 1D ). Scutellum finely rugulose, mainly on posterior region; a pair of elevations near midline at anterior half; length at midline 4.60, maximum width 5.30. Hemelytra finely punctate throughout; embolar groove (=nodal suture) present reaching second abdominal segment; membrane well developed; hindwing with Mp and CuA veins merging at distal third; R+Ma gently curved posteriorly at apex; wing groove of mesoscutellum widened, slightly convex. Mesepimeral projection extending posteriorly in dorsal view, reaching middle of abdominal tergum II; wing knob rounded. Metanotum densely pubescent. Postalar metathoracic projection with lateral margin folded downward, gutter-shaped; length of postalar projection 0.82× length of mesepimeral projection. Metaxyphus swollen medially at anterior two-thirds, slightly depressed at posterior third, with distolateral margins converging at apex, forming an acuminate point.

Legs. Protibia at mid-length with lateral surface slightly narrower than mesal surface. Middle and hind legs light-brown with dark spots. Measurements as follows: foreleg, femur 6.20, tibia 4.00, tarsomeres 1–2 1.10; middle leg, femur 6.80, tibia 6.60, tarsomeres 1–3 3.05; hind leg, femur 8.00, tibia 8.80, tarsomeres 1–3 4.70.

Abdomen. Pubescence covering connexiva and mediosternites ( Fig. 1B ). Air straps lanceolate, linear, slightly constricted at mid-length, without dorsal sac. Male genitalia: Paramere elongate, narrowing towards apex, which is distinctly twisted upward and inward. Dorsal arms of phallosoma parallel, slightly convergent at apex, entirely covering diverticulum in dorsal view ( Fig. 1E ); diverticulum elliptical, with apex rounded ( Fig. 1F ); phallosoma weakly curved in lateral view, without dorsocaudal elevation ( Fig. 1G ); ventroapical protuberance faintly developed ( Fig. 1G ).

Female. Paratypes (n = 3), length 32.0–33.5 (mean = 32.75); maximum width 13.0–13.7 (mean = 13.35). Similar to the male in general structure and coloration, except for the subgenital plate, which bears a distal tuft of setae, a feature common to females of all species of Belostoma .

Diagnosis. This species can be easily recognized by the following combination of characters: eyes triangular, article II of labium shorter than III, anteoculus longer than interoculus, abdominal pubescence entirely covering connexiva and mediosternites, and dorsal arms of phallosoma parallel.

Comparative note. Belostoma zecai Stefanello sp. nov. generally resembles B. fittkaui and B. sayagoi , particularly in the abdominal pubescence, which entirely covers the connexiva and mediosternites, and the distinctly shorter article II of the labium compared to article III, a characteristic that is unique to these species (Stefanello 2021). However, the new species differs in having a less prominent, although still well-developed and projected forward, prosternal keel; a longer anteoculus compared to the interoculus; and a narrower body compared to B. fittkaui , which is of similar size. The male genitalia are quite similar among the three species, except for the dorsal arms, which are parallel in Belostoma zecai Stefanello sp. nov. and convergent in the other species of the same group.

Etymology. The specific epithet “ zecai ” is in honor to Dr. José Ricardo Inacio Ribeiro, affectionately known as Zeca. He is a distinguished expert on the evolution and taxonomy of giant water bugs and has played a significant role in mentoring the first author since his undergraduate studies, acting as his main collaborator ever since.

Type material. HOLOTYPE, ♂: BRAZIL, Maranhão, Alto Parnaíba, Nascentes do Rio Parnaíba National Park, Fazenda Galileia , Riozinho River , 10°00’47.1”S, 46°20’14.4”W, 14.ix.2023, F. Stefanello, J.I.S. Jesus, M.A.G. Almeida & M.A.G. Almeida colls. ( CEIOC) . PARATYPES: BRAZIL, Maranhão, Alto Parnaíba, Nascentes do Rio Parnaíba National Park, Fazenda Galileia , Riozinho River , 10°00’47.1”S, 46°20’14.4”W, 14.ix.2023, F. Stefanello, J.I.S. Jesus, M.A.G. Almeida & M.A.G. Almeida colls. (2♀ CZMA) ; same locality and collector (1♂, 1♀ MZUSP) .

Distribution. This species is known only from the type locality in the protected area Nascentes do Rio Parnaíba National Park, state of Maranhão, northeastern Brazil ( Fig. 2 ).

Figures

FIGURE 1. Male holotype of Belostoma zecai Stefanello sp. nov. (A) dorsal habitus; (B) ventral habitus highlighting the abdominal pubescence (arrow); (C) details of head and pronotum highlighting the triangular eyes and lateral folds of the pronotum not extending to the posterior part (arrow); (D) lateral view of the head showing details of the labium and prosternal keel (arrow); (E) dorsal view of phallosoma showing the condition of the dorsal arms; (F) ventral view of phallosoma showing the condition of the diverticulum; (G) lateral view of phallosoma showing the ventroapical protuberance of the diverticulum. ant—anteoculus, int—interoculus, is—interocular space, lab—labium, prk—prosternal keel, II and III refer to the second and third article of the labium, con—connexivum, mst—mediosternite. Scale of 5 mm valid only for A and B.

FIGURE 2. (A) Type locality of Belostoma zecai Stefanello sp. nov. in the Riozinho River in Nascentes do Rio Parnaíba National Park; (B, C) Collection records of species in the Belostoma fittkaui species group. (B) Belostoma zecai Stefanello sp. nov. (yellow star) in Nascentes do Rio Parnaíba National Park (polygon in red); (C) B. fittkaui De Carlo (yellow circles) and B. sayagoi De Carlo (yellow triangles). BA, MA, PI, and TO refer to the Brazilian states of Bahia, Maranhão, Piauí, and Tocantins, respectively. All coordinates in the map are presented in decimal degrees.