Platynectes (Platynectes) bicolor, Short & Benetti & Gustafson, 2020

Short, Andrew Edward Z., Benetti, Cesar J. & Gustafson, Grey T., 2020, New records of Platynectes (s. str.) diving beetles from South America with description of two new species (Coleoptera: Dytiscidae: Agabinae), Acta Entomologica Musei Nationalis Pragae 60 (2), pp. 437-447 : 439-440

Platynectes (Platynectes) bicolor sp. nov.

( Figs 2 , 6–7 , 10–11 , 15 )

Type material. HƟĿƟτΥΡ*ú:♁ ( INPA), labelled: ‘BRAZIL: Goiás State: Alto Paraíso County / -14.27741, -47.75075; 967 m / Rio dos Couros, nr. Alto Paraíso / small stream, roots & organic / matter on sand/rock; 21.ii.2018 / Benetti & team; BR 18-0221-01B’, ‘DNA VOUCHER / Extraction #/ SLE-1625’ ( INPA). PΑ*©ΑτΥΡ*úඌ(2 exs): BRAZIL: GοΙá S SΤΑΤΕ: Same data as holotype (1 ♀, SEMC). MΑΤο G RοSSο Βο SƲL SΤΑΤΕ: c. 15 km E Aquidauana on plateau, -20.4509°, -55.6218°; 380 m, 22.vi.2018; leg. Hamada & team, Detritus and washing roots at margin of rock, BR 18-0622-03D (1 ♁, SEMC, DNA Voucher SLE-1989).

Description. Body oval, evenly curved and continuous between pronotum and elytron, lateral margins slightly curved.

Coloration ( Fig. 2 ). Head black, with yellow triangular shaped spot in the middle of head, between eyes; antenna and palpi dark reddish/orangish. Pronotum black with a yellow well-marked spot on anterolateral angles. Elytron black with two yellow spots, one small, slightly posterior of middle near lateral margin and one larger, subapical; epipleuron black with two orange spots near anterior inner margin. Prosternum and prosternal process dark reddish; metepisternum, metaventrite and metacoxal plates dark brown. Fore- and midlegs orangish; metalegs reddish. Abdominal ventrites orangish with a few, little darker area on ventrite II medially; posterior margin of last ventrite a little darker.

Head broad and short, anterior clypeal margin broadly rounded; entire dorsal surface of head with small irregular pentagonal cells, each cell with very fine punctures; clypeus with two short and deep impressed rows of punctures anteriorly; labrum anteriorly deep concave, with a row of setae.

Pronotum broad and short; lateral bead distinct and broad, evenly curved, about half width of antennomere V; posterior margin sinuous, medially produced; posterior angles rounded; surface shiny, covered with fine microreticulation of irregular rounded to pentagonal cells, cells with fine punctures.

Elytron with lateral margins mostly evenly curved to slightly angulate apex, lateral epipleural carina distinctly visible throughout length; surface covered with weakly impressed, but distinct microreticulation of large irregular cells, with fine punctures; elytral epipleuron with basally wide, suddenly narrowed on level of metacoxal and then evenly narrow, ending on level of ventrite IV.

Legs. Fore- and midlegs slender, surfaces finely punctate; protibial apices with largest spine longer than protarsomeres I+II; protarsal claws slender, evenly curved; mesotibal apices with longest spine about the length of mesotarsomeres I; mesotarsal claw elongate slender, slightly sinuate, with half the length of mesotarsomere I. Metatrochanter apically with anterior margin almost straight, with reticulation of transversal elongated cells; metafemur with fine well impressed reticulation composed of elongate cells, almost imperceptible weakly impressed punctation; metatibia with reticulation of transversal elongated cells; metatibial spurs slender, anterior slightly shorter than metatarsus I, posterior spur slightly longer than metatarsus I.

Ventral part. Prosternum medially moderately long, longitudinally swollen. Prosternal process broad, lateral margins curved to somewhat spatulate apex, slightly convex, and laterally margined; with fine punctures and weak impressed reticulation. Metaventrite with anterior process broad, with broadly curved emargination for reception of prosternal process; lateral parts of metaventrite (‘wings’) narrow, WC/WS = 5; surface smooth, microreticulation well impressed, composed of elongate, irregular cells, punctation nearly imperceptible. Metaventral process with well impressed reticulation of transversal elongate cells. Metacoxae with microreticulation well impressed, composed of short, rectangular cells laterally and medially; punctation irregular, nearly imperceptible; metacoxal lines distinct, slightly divergent anteriorly.Abdominal ventrites broad, margined, smooth and unmodified, with fine weakly impressed reticulation, composed of irregular elongate transversal cells, punctation nearly imperceptible.

Male genitalia ( Figs 6–7 ). Median lobe in left lateral ( Fig. 6 ) view weakly curved, with nearly straight inner margin, apex rounded, weakly expanded, dorsal surface with small pores, nearly imperceptible; ventral groove in right lateral view ( Fig. 7 ) narrow, even in width throughout its length.

Variation. The yellow spot on head is more triangular, with regular sides in females, more elongate shaped in male. Females also appear slightly wider and rounder in dorsal habitus than male. The yellow spots on the elytron are a little larger in the specimen from Mato Grosso do Sul.

Measurements. Male: TL = 6.0 mm, TL-h = 5.5 mm, TW = 3.5 mm; female: TL = 6 mm, TL-h = 5.5 mm, TW = 4.0 mm.

Differential diagnosis. Having venter primarily dark colored, but abdomen lightly colored, the new species is included in the P. ornatifrons species group. Platynectes bicolor sp. nov. is most similar to P. ornatifrons having a darkly colored venter with orange abdomen, and elytra with four yellow maculae. However, it can readily be distinguished from P. ornatifrons by being smaller in size (6.0 mm compared to 7.25 mm) and having an evenly rounded habitus, compared to the more elongate oval appearance of P. ornatifrons . Additionally, the pronotal lateral margins of P. bicolor are straighter relatively to the more strongly arced and rounded appearing pronotal margins of P. ornatifrons . Finally, the elytral discal punctures forming a series of lines (serial punctures) that are present in P. ornatifrons are absent in P. bicolor , being obscured by denser elytral sculpturing. This latter character (‘subserial punctures’ easily distinguished) was used as a diagnostic feature by SIJΑ*©Ρ (1882) for P. ornatifrons .

Etymology. An adjective bicolor [= two-colored] referring to the contrasting coloration of the dorsal and ventral surfaces of the new species.

Habitat. Both series of specimens were collected from similar habitats: from small pools in rock with root mats near streams. The specimens from Goiás were not collected in the main river, but in a small side trickle over rock that also contained significant rootmat growth ( Fig. 10 ). The specimen from Mato Grosso do Sur was collected by taking rootmat growing on rock in a side seepage and washing it in a pan of water ( Fig. 11 ).

Distribution. This species is known from two distant localities ( Fig. 15 ) but both situated on the Brazilian Shield.

Figures

Figs 2–5. Dorsal habitus images of Platynectes spp. 2 – P. bicolor sp. nov.; 3 – P. colombicus sp. nov.; 4 – P. ornatifrons Sharp, 1882, syntype; 5 – P. parananus Sharp, 1882, holotype.

Figs 6–9. Median lobes of the adeagus. 6–7 – P. bicolor sp. nov.: 6 – left lateral view; 7 – right lateral view. 8–9 – P. colombicus sp. nov.: 8 – left lateral view; 9 – right lateral view. Scale bars = 0.5 mm.

Figs 10–11. Habitat of Platynectes bicolor sp. nov. 10 – Brazil: Goiás, collecting event BR18-0221-01B; 11 – Brazil: Mato Grosso do Sul, collecting event BR18-0622-03D.Arrows indicate rootmat microhabitat where specimens were collected.The water was clear in both stream-seepages; the pictures were taken after the water was muddied by collecting efforts.

Figs 12–16. Distribution of Platynectes ‘Clade II’ sensu TƟUඌඌΑιΝτ et al. (2017) in South America. Circles represent previously published localities; stars represent localities newly reported in this paper.