Rompindessus jenisi sp. n. by present designation.

Of the set of structural features generally used to classify Bidessini, the following combination is present in this taxon: 1) occipital line present; 2) basal pronotal striae present; 3) basal elytral striae absent; 4) sutural line on elytron absent; 5) basal epipleural transverse carina absent; 6) clypeus with thick anterior bead (or margin); 7) longitudinal elytral carina on disc absent; and 8) parameres two-segmented. Moreover, the male pro- and mesotarsus appear stout, and distinctly dilated laterally; the pronotum is comparably long and parallel-sided and the colour of beetle is conspicuously dark orange. This differentiates Rompindessus gen. n. from all other Bidessini. In the key to Bidessini genera by Miller and Bergsten (2016)Rompindessus keys out to Platydytes Biström, 1988, which only occurs in sub-Saharan Africa. Apart from geography, Rompindessus can be distinguished from Platydytes by the thickly bordered clypeal margin (finely bordered to indistinct in Platydytes), the enlarged, laterally expanded male pro- and mesotarsomeres I-III, the dark orange colouration with dark speckles on elytra, and the more discontinuous body outline between pronotum and elytra.

Named after the collecting locality, Rompin village, and the ending – dessus as used for many genera in Bidessini.

Male (NHMW). “Malaysia, Pahang, 40km W Rompin, Selendang, 29.4.–6.6., leg. I. Jenis, 1993”.

Situated around Malaysia, Pahang, Selendang, between these points 2.622516°N 103.334934°E / 2.609909°N 103.382443°E / 2.643574°N 103.409337°E, it is not known where exactly this particular beetle was discovered. The altitude is around 50 to 250m (Jeniš pers. comm.). According to satellite images in Google Earth, the lower elevations are now heavily transformed into oil palm plantations.

Habitus elongate oval. Measurements: TL = 2.45 mm, TL-H = 2.15 mm; MW = 1.1 mm; elytra 3.5× longer than pronotum.

Colouration. Head, pronotum and elytron dark orange, the latter with few darker speckles (Fig. 1). Ventral side and appendages testaceous.

Figure 1. 

Rompindessus jenisi gen. et sp. n., holotype, habitus (A), head, pronotum and base of elytra (B). White arrows point to the thick anterior bead of clypeus.

Surface sculpture. Head with distinct microreticulation posterior of occipital line; finer microreticulation along eyes and clypeus, frons without microreticulation and thus shiny / polished but with few setiferous punctures. Pronotum and elytron with distinct microreticulation and sparse setiferous punctation. Ventral surfaces polished, with faint and sparse setiferous punctation.

Structures. Head with distinct occipital line and broadly beaded clypeus (Fig. 1A). Pronotum with faint lateral bead and distinct basal striae, the latter are curved inwards (Fig. 1). Elytron without basal striae and without sutural line. Basal epipleural transverse carina absent. Metathoracic wings apparently fully developed (not dissected but seen from opening caused by previous removal of the last three ventrites). Pro- and mesotarsus appearing stout as they are distinctly dilated laterally.

Male. Median lobe of aedeagus simply curved (Fig. 2A, B), lateral lobes (parameres) of two parts and of general Bidessini type (e.g. as figured for Uvarus lacustris (Say, 1823), Leiodytes evanescens (Boheman, 1848), Platydytes incognitus Biström, 1988 and Bidessus unistriatus (Goeze, 1777) in Biström (1988)) (Fig. 2C).

Figure 2. 

Rompindessus jenisi gen. et sp. n., holotype, median lobe of aedeagus, ventral view (A), lateral view (B), paramere, lateral view (C).

Female. Unknown.

Named after Ivo Jeniš, discoverer of this species. The specific epithet is a substantive in the genitive case.

Only known from the type locality.

Unknown.

Hydroporus evanescens Boheman, 1848

Very small, yellowish diving beetles (1.4–2.2 mm for the known species, 2.7 mm with the new one described below) with black markings on elytra. Shape of body globular to elongate, widest in middle, not flattened. 1) Occipital line present; 2) basal pronotal striae present; 3) basal elytral striae present; 4) sutural line on elytron absent; 5) basal epipleural transverse carina absent; 6) clypeus with fore margin narrowly and finely bordered, sometimes unmodified; 7) longitudinal elytral carina on disc absent; and 8) parameres two-segmented.

Includes 27 species (Nilsson 2016), widely distributed in the Aftrotropical, Oriental and Palearctic regions.

Male (ZSM). “Malaysia, Pahang, Kuala Lipis, old rubber plantation, iv.1997, Balke & Hendrich”. Paratypes, 2 males (CSR, ZSM), 1 female (CSR) “S Vietnam (Cat Tien), 120 km NNE Ho Chi Minh, Cat Tien NP, 3.–15.07.1995, A. Napolov leg.”; 2 males (CWT) “Vietnam, Nam Cat Tien, 200 m, 17-25-VI-1995, leg. Malicky”; 3 males, 2 females (CWT, NHMW, TFRI). “Vietnam, Dong NAI, Nam Cat Tien NP, 120 m, 18-IX-1998, leg. L. J. Wang”.

The type locality was around 4.200104°N 102.061570°E, altitude 100m. The entire region is now heavily transformed into oil palm plantations. The paratype locality was in Nam Cat Tien National Park, as a rough reference we obtained a position at the forest border 11.422096°N 107.427578°E.

Habitus elongate oval. Measurements: TL = 2.7 mm; TL-H = 2.4 mm; MW = 1.3 mm; elytra 4.2× longer than pronotum.

Colouration. Beetle dark yellow with few darker basal pronotal markings and darker pattern on elytra (Fig. 3).

Figure 3. 

Leiodytes kualalipis sp. n., holotype, habitus (A), head, pronotum and base of elytra (B).

Surface sculpture. Head with distinct microreticulation posterior of occipital line; faint to extremely faint microreticulation along eyes and clypeus, frons without microreticulation and thus shiny / polished but with few setiferous punctures. Pronotum and elytron without microreticulation but with dense, coarse setiferous punctation. Ventral surfaces mostly polished, metaventrite, metacoxa and ventrites 1–3 with large punctures bearing short setae, distance between punctures approximately the diameter of a single puncture (similar to Leiodytes vietnamensis Wang, Satô & Yang, 1998, p. 165, Fig. 6A in their work).

Structures. Head with faint occipital line and depressed before clypeus leading to the impression that the clypeus is broadly beaded (Figs 3B, 4). Pronotum with faint lateral bead and distinct basal striae, the latter are strongly directed inwards (Figs 3B, 4). Elytron with basal striae but without sutural lines. Basal epipleural transverse carina absent. Flight wings apparently fully developed (not dissected but seen from opening caused by previous removal of the last three ventrites). Pro- and mesotarsus not conspicuously dilated laterally.

Figure 4. 

Leiodytes kualalipis sp. n.: male paratype, SEM of head, pronotum and base of elytra.

Male. Median lobe of aedeagus in lateral view thin and pointed apically, apical portion spatulate in ventral view (Figs 7A, B); lateral lobes (parameres) of two parts and distally broad, with broad “nose” or broadly twisted (Fig. 7C).

Female. Similar to male, but surface dull due to presence of strong microreticulation dorsally and ventrally (Figs 5, 6).

Figure 5. 

Leiodytes kualalipis sp. n.: female paratype, SEM of microreticulation on metasternum.

Figure 6. 

Leiodytes kualalipis sp. n.: female paratype, SEM of last ventrite with deep suture apically.

Figure 7. 

Leiodytes kualalipis sp. n., median lobe of aedeagus, ventral view (A), lateral view (B), paramere, lateral view (C).

This is the largest species of Leiodytes and well characterised by its size as the other species in the region are distinctly smaller (below 2.2 mm or even below 2 mm long, see e.g. Régimbart 1899; Wang et al. 1998). Besides the larger size, this new species has a unique feature: the last ventrite has a deep suture apically (Fig. 6). This might be an autapomorphy for the new species.

This is, to our knowledge, the second species reported from the Malayan Peninsula, L. nicobaricus (Redtenbacher, 1867) being the other one (Balke et al. 2004; Hendrich et al. 2004).

Named after the type locality, Kuala Lipis Town. The species name is a noun in apposition.

A species with a wide geographic range, known from the type locality in West Malaysia as well as from Southern Vietnam. The distance between these two localities is roughly 1,000 km measured as a straight line across the Gulf of Thailand.

The holotype was collected in shallow water, among dense layers of rotten leaves, in a shaded forest pool situated in an old rubber plantation overgrown by secondary forest (Fig. 8). The species was associated with the Dytiscidae: Copelatus sp., Hydaticus pacificus pacificus Aubé, 1838 and Hyphydrus birmanicus Régimbart, 1888.

Figure 8. 

Habitat of Leiodytes kualalipis sp. n. near Kuala Lipis, West Malaysia. Drawing of beetle by D. Paramonov (Riga).

In Vietnam, the species was collected in shallow water made by jeep on a path. Syntopically occurring dytiscid species included Leiodytes nicobaricus (Redtenbacher, 1867), Hydroglyphus orientalis (Clark, 1863) and Sandracottus maculatus (Wehncke, 1876).