Platambus elongatus, Bian, Dong-Ju & Ji, Lan-Zhu, 2008

Bian, Dong-Ju & Ji, Lan-Zhu, 2008, A new species of Platambus from China (Coleoptera: Dytiscidae), Zootaxa 1683 (1), pp. 32-38 : 33-36

Platambus elongatus sp. nov.

( Figs. 2, 4, 6, 8, 10 , 12, 14, 16 )

Type material. Holotype: male, CHINA: Hainan Province, Qiongzhong County, 600 m, 18 January 1996, leg. L. Ji & M. Wang. Paratypes: 1 male, 1 female, the same date as holotype.

Diagnosis. Within the sawadai- group recognized by its broadly oval shape, rather convex form, indistinct pronoto-elytral angle, and the strong puncturation on the upper surface. It is similar to P. s a w a d a i (Kamiya, 1932), but can be easily distinguished by its broader oval, less convex shape; larger punctures on elytral mesh intersections and on the anal sternite; more elongate parameres in the male genitalia; and by the different shape of the process of the prothoracic ventrite (“prosternal process”). The aedeagus is strongly curved in lateral view, evenly tapered in apical part, while sharply tapered in apical part in P. sawadai ; the apex of the aedeagus in dorsal view is rounded in P. elongatus sp. nov., while it is distinctly pointed in P. sawadai .

Description. Body broadly oval, narrowed to apex, distinctly convex ( Fig. 2 ).

Length of body: Total length 7.5–7.8 mm, width 4.4–4.6 mm.

Head: dark rufo-brownish with two indistinct interocular yellowish spots on vertex. Reticulation distinct, meshes irregular in size, much smaller on disc, with 1–4 small punctures within them; some larger punctures at intersections. Distinct row of punctures alongside eyes. Clypeal groove distinct.

Pronotum: ferrugineous, lighter than head. Reticulation weakly impressed on disc, more distinctly near lateral margin; meshes with 1–5 punctures much larger than those on head and elytra; also with some larger punctures at intersections. Irregular rows of large punctures along anterior margin and lateral part of posterior margin. Lateral margin ridged, evenly curved.

Elytra: darker than pronotum, without spots. Elytra covered with some very large irregular punctures, more dense laterally. Reticulation consisting of small polygonal meshes with one puncture within them; some larger punctures at some intersections. Sutural row of punctures complete; punctures medium–sized and well– spaced, almost in a straight line. Epipleura mostly yellowish-brown, distinctly broadened at base, rather narrowed as far as posterior metasternum, evenly tapering to apical part ( Fig. 4 ).

Underside: ferrugineous. Process of prothoracic ventrite (= “prosternal process”) flattened, elongate, distinctly broadened on anterior 2/3, produced into a short, sharp point ( Fig. 8 ). Lateral process of metaventrite (= “metasternal wings”) relatively narrow ( Fig. 10 ). Metaventrite coarse, indistinctly reticulate; meshes very small, sometimes with one puncture within them. Metatrochanters elongate, produced in a long and sharp point distally. Femora of all legs longitudinally reticulate; metafemora with a row of short setae at distal posterior angles. Ventral surface of metatibiae with two irregular rows of strong short setae on outer half. Sternites 1–3 longitudinally reticulate, of which the third sternite reticulate indistinctly; polygonal meshes of sternite 4 very small on anterior 1/3.

Male: protarsi and mesotarsi slightly dilated and with small pads on first three tarsomeres. Anal sternite coarsely sculptured on most of its surface, with reticulation on anterior 1/6 consisting of very small meshes; with numerous large punctures on posterior 5/6 ( Fig. 6 ). Posterior margin slightly concave at middle. Parameres elongate, basal piece transverse, apical piece 2.6 times as long as base ( Fig. 12 ). Aedeagus, in lateral view, strongly curved on basal part, flattened and broadened, evenly tapered in apical 1/2 with narrow apex ( Fig. 14 ); in dorsal view, broad, slightly and evenly tapered towards apex, with a broad rounded apex ( Fig. 16 ).

Female: similar to male, but head and pronotum dark testaceous, elytra black. Elytral large punctures denser than male. Anal sternite black, coarsely punctured, deep punctures denser than male, and distinctly sculptured except basal 1/6; posterior margin finely bordered and flattened at middle.

Distribution. This species is known only from the type locality.

Etymology. Specific name from the Latin elongat - = extended, in reference to the slender apical part of the parameres; to be treated as adjectival for the purposes of nomenclature.

Figures

FIGURES 1 – 10. Platambus wulingshanensis, male: 1, 3, 5, 7, 9; Platambus elongatus sp. nov., male (holotype): 2, 4, 6, 8, 10. 1 – 2: Habitus and colour pattern; 3 – 4: Epipleura; 5 – 6: Anal sternite; 7 – 8: Process of prothoracic ventrite; 9 – 10: Lateral process of metaventrite. Scale bars: 1 – 4 = 1 mm; 5 – 10 = 0.3 mm.

FIGURES 11 – 16. Platambus wulingshanensis, male: 11, 13, 15; Platambus elongatus sp. nov., male (holotype): 12, 14, 16. 11 – 12: Right paramere; 13 – 14: Aedeagus, in lateral view; 15 – 16: Aedeagus, in dorsal view. Scale bars = 0.25 mm.