Hypsilara royi gen. n. and sp. n. (Coleoptera, Elmidae, Larainae) from Southern Venezuela, with a revised key to Larainae of the Western Hemisphere

Abstract Here we describe a new genus, for a new species of riffle beetle, Hypsilara royi gen. n. and sp. n., from the tepui Cerro de la Neblina in southern Venezuela. This new genus can be distinguished from all other laraine genera by its small size (ca. 4.5 mm) and the presence of a shallow, wide, V-shaped groove across the apical third of the pronotum. An updated key to the genera of Western Hemisphere Larainae is provided, along with information on habitat and collection methods for this taxon.


introduction
The Elmidae are a cosmopolitan family of beetles common in a variety of running water habitats. They are known for their "leggy" appearance, with long legs and claws that aid in clinging to rocks and other detritus in fast-flowing water. Members of the subfamily Larainae are atypical among the riffle beetles, as the adults do not live submerged, but on water-splashed rocks and in moist detritus at the water's edge.
Currently, there are 26 genera of laraines described, with ten occurring in the Neotropical Region. The Central American and West Indian fauna was revised in 1991 by Spangler and since then, two other genera have been described from the tepuis of southern Venezuela, Roraima Kodada and Jäch, from Mount Roraima, and Neblinagena Spangler, from Cerro de Neblina. Specimens of the new genus described here were collected from Cerro de la Neblina, the "Mountain of the Mists" in southeastern Amazonas State, Venezuela (Fig. 1). Cerro de la Neblina is a 647 km 2 precipitous sandstone mesa or tepui, one of numerous high, tabletop mountains that occur in northern South America (Spangler 1985). These mesas are the eroded remains of a former large plateau, the Guiana Highland Shield and rise sharply from the tropical rain forests, with their tops often obscured by a dense cloud cover.

Methods
Specimens of this new taxon were collected during a biological survey of Cerro de la Neblina in 1985. They were photographed using a Canon EOS 70D with a Visionary Digital imaging system and photos were stacked using CombineZM image editing software.
For scanning electron micrographs, the specimen was dehydrated in 100% ethanol and cleaned with an insect pin and fine brush. The specimen was then affixed to an SEM stub using carbon tape and coated with gold. Micrographs were taken using a Leo 1550 Scanning Electron Microscope at the Microscopy and Analytical Imaging Laboratory at the University of Kansas.
The genitalia were extracted from relaxed specimens through the caudal opening in the abdomen. The genitalia were then cleared in heated potassium hydroxide for thirty minutes, rinsed with water, and temporarily mounted in glycerin for observation and illustration. The cleared genitalia were then placed in a glass genitalia vial below the specimen for storage.
Hind wings were removed and dry mounted on slides using methods outlined in Kukalová-Peck and Lawrence (1993). Veins were homologized using terminology from Kukalová-Peck and Lawrence (1993) and Kodada and Jäch (2005). Illustrations were made in pen and ink using a camera lucida attached to a Olympus SZX7 microscope. Images were edited in Adobe Illustrator and Adobe Photoshop. Specimens were deposited in the following collections: Diagnosis. This genus can be distinguished from all other laraine genera by its small size (ca. 4.5 mm), and the presence of a shallow, wide, V-shaped groove across apical third of the pronotum (Fig. 10). Description. Body elongate, form gradually widening to posterior two-thirds of elytra then converging to elytral apex, moderately convex (Fig. 2). Integument clothed with dense, recumbent pubescence.
Pronotum widest at base, weakly sinuate laterally, becoming evenly arcuate over head; base trisinuate, broadly sinuate on each side and much more narrowly so immediately anterior to scutellum; anterolateral angles explanate and broadly depressed; Hypsilara royi gen. n. and sp. n. (Coleoptera, Elmidae, Larainae) from Southern Venezuela... 29 posterolateral angles slightly explanate, declivous, not depressed; middle of base with two short, broad, prescutellar cariniform ridges, each ridge with distinct lateral depression ( Fig. 10). Pronotum with V-shaped discal groove; lateral branches of groove shallowly depressed, almost confluent with sublateral arcuate-sinuate groove but interrupted by short carina laterally; stem of Y-shaped groove shallow; sublateral carina short, evident at base then merging with lateral margin. Scutellum flat, wider than long, subtriangular. Elytron with ten longitudinal rows of deep punctures; without accessory row of punctures; without complete longitduinal carinae; apex rounded, not prolonged ( Fig. 11). Prosternum very long anteriorto procoxae, about as long as prosternal process; moderately reflexed along anterior margin (Fig. 3). Prosternal process broadly triangular between procoxae; apex narrowed and rounded. Mesoventrite with deep, broadly V-shaped depression on midline for the reception of apex of prosternal process. Metaventrite with disc shallowly, broadly depressed on posterior two-thirds; with longitudinal groove deepest and broadest on posterior third of midline (Fig. 14). Legs with visible portion of procoxae transverse and trochantin visible. Claws prominent and without teeth (Figs 15, 16).
Hind wing lightly pigmented. Radial bar strong; radio-medial loop and radial cross vein r4 distinct; radial cell incomplete; medial fleck absent; media posterior MP 1+2 strong, distinct; medial spur long, nearly reaching wing margin; first and second cubito-anal cells present; medial field with five free veins reaching margin (medial spur not included); anal field with single vein; apical field with two lightly pigmented bands (Fig. 5).
Abdomen with five ventrites. First ventrite with paired, broad carinae posterior to metacoxae extending almost to hind margin of ventrite (Fig. 17).  Etymology. Hypsilara from the Greek "hypsos" meaning "aloft", from its elevated habitat on Cerro de Neblina, and "lara", from the subfamily name, Larainae. The gender is feminine.
Remarks. Hypsilara royi sp. n. was also collected from a flight intercept trap operated in the lowland rain forest (140 m elev.) near the base camp (00°50'N 66°10'W) (Fig. 1). PJS had designated this single male specimen as a new species; based on genitalia differences, though specimens bearing genitalia similar to the base camp specimen were collected at the type locality of Hypsilara royi sp. n. Therefore, we decided not to designate it as a new species at this time.
Clypeus anteriorly with shallow arcuate emargination. Labrum subrectangular; surface with fine, dense punctation and densely fringed with long, fine, golden, hairlike setae; anterolateral angles rounded but not expanded laterally; lateral margins not expanded, with a long, dense tuft of golden hairlike setae curled over margin. Labium with long, dense setae. Last segment of maxillary palpus broad and bearing sensillae on flattened apex (Fig. 9).
Pronotum 1.4 mm long, 1.5 mm wide; with deep sinuate sublateral groove, which extends from apical third of pronotum to base; lateral margins slightly sinuate; anterolateral angles obtuse, distinctly explanate and broadly depressed behind each angle; apex slightly sinuate and with broad lobe medially; posterolateral angles obtuse, slightly explanate, declivous, not depressed adjacent to each angle (Fig. 10); discal area with fine, dense punctures, punctures separated by a distance equal to or less than their diameter; cuticle microreticulate.
Prosternum very long in front of procoxae; bearing a tuft of sparse, long, dark brown setae and dense golden setae apicomedially. Prosternal process (Fig. 3) triangular, broad at base and tapering to apex; lateral margins reflexed; middle moderately longitudinally cariniform; apex narrow, rounded. Mesoventrite with a deep, broad, V-shaped depression for reception of apex of prosternal process. Metaventrite with disc depressed on posterior three-fourths, coarsely punctate behind mesocoxae, punctures becoming more sparse laterally, with large, rounded depressions scattered on disc (Fig. 14); with a deep, narrow, shining, longitudinal groove on midline of disc, groove deepest and broadest on posterior third of disc; with short, dense, golden pubescence and a patch of longer darker brown setae on each side of median groove on apical third; cuticular surface of metaventrite finely microreticulate. Procoxae and metacoxae moderately widely separated; mesocoxae slightly more widely separated. Legs long and slender. Protibiae, mesotibiae, and metatibiae ( Fig. 3) with dense spatulate pubescence distally. Tarsal claws long and stout (Figs 15, 16).
Elytron with ten rows of coarse, very deep punctures (Fig. 11); punctures separated by a distance two times the diameter of the puncture (Fig. 12); intervals with fine, dense pubescence; each larger seta surrounded by four to seven smaller setae (Fig. 13) humeral area moderately swollen; elytra margined laterally; widening to about posterior two-thirds before converging to rounded apex.
Abdomen with five ventrites (Fig. 17). First ventrite with intercoxal process broadly, shallowly depressed and distinctly carinate adjacent to metacoxae; carinae extending longitudinally behind metacoxae for almost entire length of ventrite; cuticle densely covered with setae. Last visible ventrite broadly rounded.
Female. Similar to male, except lacks the patch of longer setae apicomedially on prosternum and the patch on each side of median groove on apical third on metasternum. Genitalia as illustrated (Fig. 7).
Intraspecific variation. As noted in the "Remarks" section, the shape of the parameres of the aedeagus vary from straight and wide to narrow and curved. This species exhibits only minor variations in length, which ranges from 4.2 to 4.5 mm, and varies from a medium brown to light brown in color.
Etymology. The specific epithet, "royi" is a patronym named for Roy McDiarmid, herpetologist and biological coordinator for the survey of the flora and fauna of Cerro de la Neblina.
Habitat. The type specimen was collected from a small, shallow brook about one to two meters wide and with occasional pools about one meter deep, with a substrate of sand, boulders, and bedrock. This small tributary originates on Cerro de la Neblina and feeds the Rio Baria, which drains most of the massif. The highwater marks and polished boulders along the stream bed indicate that in times of heavy rainfall, the brook becomes scoured by flash flooding. Paratypes were collected from similar small streams at high elevations.
Water quality data obtained by using colorimetric analyses of the brook at the type-locality are as follows; pH: 4, hardness: 0, oxygen: 9 ppm. The air temperature was 21°C and the water temperature was 17°C when the analyses were made.