Celerobates, Zettel, 2009

Zettel, H., 2009, Three new genera of Ptilomerinae (Hemiptera: Heteroptera: Gerridae) from Southeast Asia, Zootaxa 2046 (1), pp. 26-42 : 28-30

Genus Celerobates gen. n.

( Figs. 1–7 )

Type species. Rhyacobates imadatei Miyamoto, 1967 (by monotypy)

Diagnosis. Middle-sized, dorsally predominately blackish Ptilomerinae with very long antennomere 1 ( Figs. 1, 2 ), prominent antenniferous tubercles, and distinct claws on hind legs. Male with weakly incrassate profemur ( Fig. 1 ), almost bare and upcurved parameres ( Fig. 4 ), and with complex lateral sclerites ( Fig. 5 ). Female with median hair line on thoracic and abdominal venter, with simple metanotum, with elongate abdomen ( Fig. 2 ), and with caudad directed spine on connexivum 7 ( Figs. 6, 7 ).

Description. Only apterous morph known. Body length 6.7–11.0 mm; female (9.9–11.0 mm) distinctly larger than male (6.7–7.7 mm). Dorsal body surface blackish, with yellowish marks (greenish if alive) only on head, pronotum, and connexiva ( Figs. 1, 2 ); femora predominately yellowish. Dorsum of head anteriorly weakly deflected, in dorsal view antenniferous tubercles prominent. Antenna ( Fig. 1 ): antennomere 1 longer than segments 2–4 combined, segment 2 distinctly shorter than segment 3, segment 4 shortest, with broad whitish sulcus near apex. Metanotum simple in both sexes. Metacetabula without process. Legs very long and slender. Profemur in both sexes with ventral row of long stout bristles; protarsus 0.6 (male) or 0.8 (female) times protibial length, first tarsomere much longer than second ( Figs. 1, 2 ). Metacoxa not elongate, without apical spine; metafemur slightly shorter than mesofemur, about three times as long as metatibia; hind leg with minute claws. Wings unknown. Abdomen elongate and straight in both sexes, in male shorter than in female; abdominal tergites 1 and 2 not fused.

Male. Profemur only weakly enlarged and without preapical tooth. Mesofemur ventrally with row of short, black spines, without ventral hair fringe. Segment 8 simple, elongate. Pygophore simple, elongate, posteriorly slightly acuminate. Proctiger ( Fig. 3 ) with blunt lateral corners. Paramere ( Fig. 4 ) long, curved dorsad, distally nearly straight, only with minute setae in distal half. Vesica ( Fig. 5 ): Dorsal sclerite strongly sclerotized only at thickened base, distally shortly bifurcate, ventrally with acute process. Ventral sclerite short, weakly curved, distally furcate. Ductus seminalis long. Paired lateral sclerites very large and complex, with one large lobe distally and five small lobes ventrally, with one small denticles at base of distal lobe and two near apex of two ventral lobes. Thin, weakly developed second pair of lateral sclerites near margin on inner face of vesica's lateral lobes.

Female. Venter from anterior fourth of mesosternum to middle of sternite 7 with very narrow median area covered with pale appressed hairs which are distinctly longer than normal pubescence. Abdominal segments 1–6 simple. Connexiva 3–7 slightly flapped mediodorsad and more or lesser covering lateral parts of tergites ( Figs. 2 , 7 ); connexivum 6 without process; connexivum 7 with distinct, caudad directed spine ( Figs. 6, 7 ). Tergites 7 and 8 and proctiger simple, directed straight posteriad ( Figs. 6, 7 ). Sternites medially flattened (depressed); sternite 7 almost as long as sternites 5 and 6 combined, medially protruded posteriad, but without distinct mediocaudal lobe. Gonocoxa directed caudad, not exposed, but almost completely withdrawn into sternite 7.

Comparative notes and discussion. Andersen and Chen (1995) have shown in their phylogeny of Rhyacobates species that imadatei does not belong to the monophylum comprising Pleciobates , Heterobates , and Rhyacobates . This clade can be expanded by two genera described later: Andersenius Zettel and Chen, 1996 and Pleciogonus Chen, Nieser & Wattanachaiyingcharoen, 2002 ; both are very closely related to Pleciobates (see Zettel and Chen 1996, Chen et al. 2002). Several diagnostic, but probably plesiomorphic characters, e.g., the row of spines on the male's mesofemur and the small, but distinct claws on the meso- and metatarsi, distinguish Celerobates from this genus group, but ally it with Potamometropsis Lundblad, 1933 . There are strong similarities in the paramere between C. imadatei and the type species, Potamometropsis obnubila Lundblad, 1933 from Sumatra, but less so than with the other species of Potamometropsis . However, the very long antennomere 1, the female's elongate abdomen, and the presence of distinct, long connexival spines in the female (usually absent or very short in Potamometropsis ) separate Celerobates from Potamometropsis . Most ptilomerine genera (e.g., Pleciobates , Andersenius , Pleciogonus , Heterobates , most species of Potamometropsis s.l.) also differ from Celerobates in possessing long pilosity in the distal half of the male's paramere. Celerobates also differs distinctly from the clade Rheumatogonus + Jucundus as proposed and described by Zettel and Thirumalai (2001), e.g., the dark colour, the weakly deflected head, the long antennomere 1, and the absence of indentations on the claws of the foreleg.

Polhemus and Zettel (1997) stated that "the endosomal sclerites of ' Rhyacobates ' imadatei seems to be unique in possessing, in addition to the normal medial sclerites, very large lateral sclerites that upon eversion display a complex array of lobes and comb-like structures." These details were already depicted by Miyamoto (1967), and the vesica is here described by standard terminology (following Andersen 1982) and illustrated in the standard lateral view ( Fig. 5 ). The female of C. imadatei has a characteristic narrow median pubescent area on the thoracic and abdominal venter. Such structure is unknown in other ptilomerine genera, although different modifications do occur: The female of Heterobates has a prominent, wide and completely flat plate on its venter; and an undescribed genus from India has paired partings on the mesosternum delimiting an area of very dense pilosity. It is assumed here that these structures are convergencies developed for gliding on very turbulent water surfaces.

Distribution. Borneo.

Etymology. The genus name is composed of " celer " (Latin, adjective) meaning "fast," and " bates " from the Greek word for "stalker," commonly used for generic epithets in Gerridae . The name refers to the extremely efficient rowing abilities of C. imadatei observed by the author in Sabah (see Polhemus & Zettel 1997). Gender: masculine.

Figures

FIGURES 1–2. Celerobates gen. n. imadatei. (1) Habitus of apterous male (body length 6.8 mm), dorsal aspect. (2) Habitus of apterous female (body length 9.2 mm), dorsal aspect. © NHMW Hemiptera Image Collection, published with permission.

FIGURES 3–7. Celerobates gen. n. imadatei. (3) Proctiger of male, dorsal aspect. (4) Left paramere of male, lateral aspect. (5) Vesica of male, lateral aspect (slightly inflated). (6) Posterior part of female's abdomen, lateral aspect; (7) same, dorsal aspect. All pilosities omitted. ds = dorsal sclerite, du = ductus seminalis, gc1 = gonocoxa 1, ls = left lateral sclerite, pr = proctiger, s6, s7 = sternite 6, 7, sls = left second lateral sclerite, t6, t7, t8 = tergite 6, 7, 8, vs = ventral sclerite.