Platynectes (Platynectes) submaculatus ( Laporte, 1835 )

Gustafson, Grey T., Short, Andrew E. Z. & Miller, Kelly B., 2016, New species of diving beetles in the subgenus Platynectes s. str. from the Guiana Shield (Coleoptera: Dytiscidae: Agabinae), Acta Entomologica Musei Nationalis Pragae 56 (1), pp. 79-102 : 92-94

Platynectes (Platynectes) submaculatus ( Laporte, 1835)

( Figs 5 , 7 , 15 )

Colymbetes submaculatus Laporte, 1835: 102 [original description].

Agabus submaculatus: AUBÉ (1838) : 321 [new combination].

Platynectes submaculatus: SHARP (1882) : 766 [new combination by suggestion].

Platynectes (Hypoplatynectes) submaculatus: GUÉORGUIEV (1972) : 38 [new combination].

Platynectes (Platynectes) submaculatus: VAZIRANI (1976) : 170 [new status by indication].

Material examined (20 spec.). GUYANA: REGION XIII: 5°0.571′N, 59°38.202′W, 524 m, Upper Potaro Camp I (c. 7 km NW Chenapau ), Potaro margin trail ; small side seepage/stream over roots & detritus; leg Salisbury & La Cruz; 11.iii.2014, GY14-0311-05B, SEMC1314189 (1 spec. SEMC) . SURINAME: SIPALIWINI DISTRICT: CSNR: Tafelberg Summit, nr Augustus Creek Camp, N3°55.600′ W56°11.300′, 600 m, 17.viii.2013, SR13-0817-03 A, SEMC0966096 – SEMC0966099 (4 spec. SEMC) ; same as previous except: leg. Short & Bloom, small stream on trail to Caiman Creek Camp, SR13-0817-02 A, SEMC1080673 (1 spec. SEMC) ; same district except: Camp 4 (high), Kasikasima , N2°58.613′ W55°24.683′, 400 m, 24.iii.2012, leg. A. Short, main seepage area, SR12-0324-01C 2012 CI-RAP Survey, SEMC1087465 , SEMC1087468 , SEMC1087469 , SEMC1088431 (4 spec. SEMC) ; same as previous except: rocky pools at base of seep, SR12-0324-01D 2012 CI-RAP survey, SEMC1088354 , SEMC1088356 , SEMC1088457 , SEMC1088361 , SEMC1088371 , SEMC1088374 , SEMC1088375 , SEMC1088383 , SEMC1088385 (9 spec. SEMC, NZCS) ; same district except: Brownsberg Nature Park , N4°56.871′ W55°10.911′, 462 m, 4.viii.2012, leg. Short, Maier, McIntosh, forested stream with lots of detritus, SR12-0804-01 A, SEMC1114113 (1 spec. SEMC) .

Diagnosis. Small sized (5.3–5.9 mm in length), elongate oval and parallel-sided in dorsal habitus, elytron with five well-demarcated yellow spots.

Redescription. Size. Male: TL = 5.4–5.9 mm, TL-h = 4.8–5.3 mm, TW = 3.1–3.4 mm; female: TL = 5.3–5.9 mm, TL-h = 4.8–5.4 mm, TW = 3.0– 3.4 mm.

Body elongate oval, lateral margins mostly-evenly curved and continuous between pronotum and elytron ( Fig. 5 ).

Coloration ( Fig. 5 ). Head orange grading into diffuse, light yellow region medially on frons and testaceous to black mediad and posteriad of eyes, in some specimens extending anteriorly around eye to lateral margin of frons. Pronotum broadly black or testaceous medially along anterior and posterior margins, black regions meeting medially in lighter, testaceous transverse band; posterolateral margins of pronotum narrowly black, lateral surfaces yellow, extending medially to dark region; scutellum testaceous. Elytron testaceous, with five yellow mostly round spots, one parascutellar, one humeral, one slightly anterior of middle near suture, one slightly posterior of middle near lateral margin, and one anteapically. Appendages of head, legs and ventral surfaces, including elytral epipleuron, pale orange to reddish, somewhat darker on thoracic sterna and metacoxae; last abdominal tergite yellow.

Structure and sculpture. Head broad and short, anterior clypeal margin broadly rounded; entire dorsal surface of head with small highly irregular cells, each cell with fine punctures, additional irregular covering of fine punctation throughout, antennae with antennomeres V–IX subserrate. Pronotum broad and short, medially with small shallow dimple; lateral bead distinct and broad, evenly curved, about width of antennomere V; surface shiny, covered with fine microreticulation of irregular cells, cells with fine punctures, additional punctation consisting of a row of large coarse punctures on anterior and posterior margin, punctures separated by ca. 0.5–1× diameter of a puncture anteriorly, posterior row mostly effaced by reticulation medially, laterally punctures separated by ca. 1–2× diameter of a puncture. Elytron with lateral margins mostly evenly curved, basally somewhat straight, apically coming to slightly angulate apex, lateral epipleural carina distinctly visible throughout length; surface covered with weakly impressed, but distinct microreticulation of large irregular cells, cells also with fine punctures; elytral epipleuron slender, evenly tapered to apex. Prosternum medially moderately long, longitudinally swollen; prosternal process broad, lateral margins broadly curved to somewhat pointed apex, surface flat to slightly curved, smooth. Metaventrite with anterior process broad, with broadly curved emargination for reception of prosternal process; lateral wings broad, WC/WS = 4; surface smooth, microreticulation very weakly impressed, composed elongate, irregular cells, weakly impressed punctation, punctures separated by ca. 3–4× diameter of a puncture. Fore- and midlegs slender, surfaces punctate, protibial apices with largest spine longer than protarsomeres I+II, reaching 1/2 length of protarsomere III; mesotibal apices with longest spine about length of mesotarsomeres I+II, mesotarsal spurs elongate slender, as long as mesotarsomere I+II; metacoxae smooth, microreticulation weakly impressed, composed of elongate irregular cells, punctation very fine and weakly impressed, punctures separated by ca. 3× diameter of a puncture, metacoxal lines distinct, broadly divergent anteriorly; hind legs slender, smooth, metafemur with fine weakly impressed reticulation composed of elongate cells, almost imperceptible weakly impressed punctation, setigerous punctures on anterior surface of metatibia and metatarsomere I, metatrochanter apically spinous, metatibial spurs slender, anterior 2/3 length as metatarsus I, posterior spur as long as metatarsus I. Abdominal ventrites broad, smooth and unmodified, with fine weakly impressed reticulation, composed of irregular elongate cells, punctation nearly imperceptible.

Male genitalia ( Fig. 7 ). Median lobe broad, in left lateral view weakly curved, medially parallel-sided, apex strongly expanded and irregularly shaped, apical 2/3 small covered in pores; ventral groove in right lateral view narrow, constricted preapically, then strongly expanded, followed by a significant narrowing at apex.

Sexual dimorphism. On average the larger specimens were females, suggesting some sexual dimorphism. However, females were not particularly variable in size.

Variation. There is some significant size variation relative to other species, but specimens have a similar shape in dorsal aspect.

Differential diagnosis. Platynectes submaculatus is most similar to P. elaskanaima sp. nov. and P. meru sp. nov. in elytral maculation pattern, having five yellow well-demarcated spots, but differs in being smaller (body length at most 5.9 mm) and less parallel-sided in dorsal habitus ( Fig. 5 ) than P. elaskanaima , but larger in body size (smallest specimen studied = 5.3 mm) and more parallel-sided in dorsal habitus than P. meru . The maculae of P. submaculatus are also much more rounded than those of P. elaskanaima and P. meru , which have several more transverse maculae. Platynectes submaculatus also has antennomeres V–IX subserrate, which helps distinguish it from the other two species. The aedeagus ( Fig. 7 ) unambiguously separates P. submaculatus from the other two species as the median lobe of P. submaculatus is very weakly curved and parallel-sided medially with an irregularly shaped apex.

Natural history. The habitat of this species appears to be very similar to P. decemnotatus , with which it has been collected on several occasions.

Distribution. Described from French Guiana and now known from Suriname and Guyana ( Fig. 15 ).

Discussion. The type specimen(s) could not be located among the Laporte material held at the Victoria Museum’s Entomology Collection (S. Hinkley pers. comm.) and may be lost.

Figures

Figs 1–6. Dorsal habitus of Platynectes species. 1 – P. meru sp. nov. 2 – P. decemnotatus (Aubé, 1838). 3 – P. elaskanaima sp. nov. 4 – P. tafelbergensis sp. nov. 5 – P. submaculatus (Laporte, 1835). 6 – P. garciai sp. nov. Scale bar = 2 mm.

Figs 7–13. Median lobe of aedeagus of Platynectes species, top row left lateral view, bottom row right lateral view. 7 – P. submaculatus (Laporte, 1835). 8 – P. elaskanaima sp. nov. 9 – P. meru sp. nov. 10 – P. decemnotatus (Aubé, 1838). 11 – P. garciai sp. nov. 12 – P. tafelbergensis sp. nov. 13 – P. agallithoplotes sp. nov.

Fig. 15. Distribution map of Platynectes species of northern South America.