Platynectes (Platynectes) decemnotatus ( Aubé, 1838 )

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 : 82-85

Platynectes (Platynectes) decemnotatus ( Aubé, 1838)

( Figs 2 , 10 , 15 , 17, 18 )

Agabus decemnotatus Aubé, 1838: 319 [original description].

Platynectes decemnotatus: SHARP (1882) : 538 [new combination by indication to species 768 in Group 3].

Platynectes (Hypoplatynectes) decemnotatus: GUÉORGUIEV (1972) : 39 [new combination; synonymy by VAZIRANI (1976): 170].

Platynectes (Platynectes) decemnotatus: VAZIRANI (1976) : 170 [new status].

Type material examined. LECTOTYPE (here designated): ♀ ( MNHN), by present designation: “Cateneur [?] Cayenne” [green and roundish handwritten label], “10 notatus Aubé” [white and handwritten label], “ Lectotype Agabus decemnotatus Aubé Gustafson, Short & Miller des. 2016” [red printed label].

Additional material examined (91 spec.). FRENCH GUIANA: “ KAW MOUNTAIN RESERVE, Kaw River Boat launch, N4°29′54.8″ W52°03′05.6″, 20 m, 8–18.ii.2005, leg. KB Miller ” (2 spec. MSBA) ; same as previous except: N4°32′57.8″ W52°12′49.7″, 286 m, forest pools nr Amazone Lodge (2 spec. MSBA) . SURINAME: SIPALIWINI DISTRICT: CSNR: Tafelberg Summit, nr Augustus Creek Camp , N3°55.600′ W56°11.300′, 600 m, 17.viii.2013, leg. Short & Bloom, small stream on trail to Caiman Creek Camp, SR 13-0817-02 A, SEMC1080669 , SEMC1080670 , SEMC1080671 , SEMC1080675 , SEMC1080681 , SEMC1080682 (6 spec. SEMC) ; same as previous except: nr

Caiman Creek Camp, N3°53.942′ W56°10.849′, 733 m, 18.viii.2013, leg. Short & Bloom, small streams with lots of plants & leaf litter, SR13-0818-03 A, SEMC1233862 , SEMC1233863 (2 spec. SEMC) ; same as previous except: 19.viii.2013, pools in forest, SR13-0819-05B, SEMC1233914 (1 spec. SEMC) ; same as previous except: forest detrital pools, SR13-0819-05C, SEMC0966146 , SEMC0966147 , SEMC1080493 (3 spec. SEMC) ; same district except: Camp 4 (high), Kasikasima , N2°58.613′ W55°24.683′, 400 m, 24.iii.2012, leg. Short, main seepage area, SR12-0324-01C 2012 CI-RAP Survey, SEMC1087462 , SEMC1087466 , SEMC1088132 – SEMC1088137 (8 spec. SEMC) ; same as previous except:rocky pools at base of seep, SR12-0324-01D 2012 CI-RAP survey, SEMC1088360 , SEMC1088362 , SEMC1088366 – SEMC1088369 , SEMC1088373 , SEMC1088376 – SEMC1088382 , SEMC1088384 , SEMC1088386 , SEMC1088387 , SEMC1088389 – SEMC1088392 (21 spec. SEMC) ; same district except: Camp 2, on Sipaliwini River , N2°10.973′ W56°47.235′, 210 m, 29–30.viii.2010, leg. Short & Kadose, inselberg, SR10- 0829-01 A 2010 CI-RAP survey, SEMC0913037 – SEMC0913039 , SEMC0913041 – SEMC0913045 , SEMC0914529 , SEMC0914532 , SEMC0914535 – SEMC0914540 , SEMC0914542 , SEMC0914544 , SEMC0914545 , SEMC0914547 , SEMC0914549 , SEMC0914551 , SEMC0914552 , SEMC0914554 , SEMC0914555 , SEMC0914557 – SEMC091559 , SEMC0914561 – SEMC0914563 , SEMC0914567 , SEMC0914568 , SEMC0914570 – SEMC0914575 , SEMC0914577 , SEMC0914580 , SEMC0914581 , SEMC0914586 , SEMC0914587 , SEMC0914858 (45 spec. SEMC, NZCS). “Amer mer.” [white handwritten label], “ decemnotatus Aubé ” [white handwritten label] (1 spec. MNHN) .

Diagnosis. Larger in size (6.6–7.7 mm in length), body robust and broadly oval, elytron with five well-demarcated yellow spots.

Redescription. Size. Male: TL = 7.2–7.7 mm, TL-h = 6.6–7.0 mm, TW = 4.32–4.7 mm; female: TL = 6.6–7.7 mm, TL-h = 6.2–7.2 mm, TW = 4.1–4.8 mm.

Body robust, and broad, broadly oval, lateral margins evenly curved and continuous between pronotum and elytron ( Fig. 2 ).

Coloration ( Fig. 2 ). 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 dark testaceous, with small, diffuse pale region at humeral angle and five well-demarcated yellow spots, one parascutellar, one slightly anterior of middle near suture, one slightly posterior of middle near lateral margin, and one anteapically which, in some specimens, extends anteriorly and posteriorly along margins. 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; anterior surface of frons and clypeus with fine, dense punctation, posterior surface of head with fine microreticulation of irregular cells, most cells also with fine punctures. Pronotum broad and short; lateral bead distinct and broad, evenly curved, about width of antennomere V; surface shiny, covered with fine microreticulation of large, irregular cells, cells with fine punctures, additional punctation consisting of a row of large coarse punctures on anterior and posterior margins, punctures separated by ca. 1–2× diameter of a puncture anteriorly, ca. 1–3× diameter of a puncture posteriorly, absent medially. Elytron broad, lateral margins 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, most 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 = 4.5; surface smooth, weakly impressed reticulation composed of elongate cells, fairly even covering of fine punctation, punctures separated by ca. 1–2× diameter of a puncture. Fore- and midlegs slender, surfaces punctate, protibial apices with several spines about length of protarsomeres I+II; mesotibal apices with few spines shorter than length of mesotarsomeres I+II, mesotarsal spurs elongate slen- der, slightly sinuate, as long as mesotarsomeres I+II; metacoxae smooth, fine reticulation composed of round cells, fine and weakly impressed punctation present, punctures separated by ca. 3–4× metacoxal lines distinct, broadly divergent anteriorly; hind legs slender, smooth, metafemur with fine reticulation composed of elongate cells, almost imperceptible, weakly impressed punctation, few setigerous punctures on anterior surface of metatibia and metatarsomere I, metatrochanter apically spinous, metatibial spurs slender, longer than metatarsus I. Abdominal ventrites broad, smooth and unmodified, with fine reticulation composed of elongate cells, fine weakly impressed punctation, punctures separated by ca. 3–4× diameter of a single puncture.

Male genitalia ( Fig. 10 ). Median lobe in left lateral view strongly curved, apex weakly expanded, strongly acute, dorsal surface covered in pores in apical 2/3; ventral groove in right lateral view strongly narrowed apically, greatly widened in basal 2/3.

Sexual dimorphism. There does not appear to be any noticeable sexual dimorphism aside from the normal pro- and mesotarsal dimorphism.

Variation. There is quite a bit of size variation, with some populations having very large and broad individuals, while others have smaller and somewhat more parallel-sided individuals. Differential diagnosis. Platynectes decemnotatus is most similar to P. submaculatus in terms of elytral maculation pattern, having five yellow well-demarcated spots on each elytron, but is much larger in body size (6.6–7.7 mm) and more broadly rounded ( Fig. 2 ). The large size, broadly oval body form, with five well-demarcated yellow spots on each elytron should prevent its confusion with any other species within the P. submaculatus group.

Natural history. This species has been collected in many stream and seep-associated habitats. Most collections are from small, forested streams with abundant detritus. A few collections were made in pools formed in or below seepages from granite inselbergs or other similar rocky outcrops ( Figs 17–18 ).

Distribution. The species is currently known from French Guiana and Suriname ( Fig. 15 ).

Discussion. In a small box of historical Platynectes specimens lent by the late Dr. Michel Brancucci from the Muséum national d’Histoire naturelle, Paris, several years ago L. Hendrich identified two historical specimens of P. decemnotatus . According to the label data the one female should be a syntype from Aubé collection. As the number of syntypes is not specified in the original description, we designate here the lectotype to fix the identity of the species.

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.

Figs 16–19. Habitat of Platynectes species. 1 – Collecting Event AS-08-060b, Venezuela, Bolivar State: Rio Aponwao (P. garciai). 2 – Collecting Event SR10-0829-01A, Suriname, Sipaliwini District, along Sipaliwini River (P. decemnotatus). 3 – Collecting Event SR13-0819-05B, Suriname, Sipaliwini District, Tafelberg Tepui summit (P. decemnotatus, P. tafelbergensis). 4 – Collecting Event SR13-0819-02A, Suriname, Sipaliwini District, Tafelberg Tepui summit (P. tafelbergensis).