Radicitus granitum Short & García, 2014

Short, Andrew Edward Z. & García, Mauricio, 2014, A new genus of egg case-carrying water scavenger beetle from the Guiana Shield (Coleoptera: Hydrophilidae: Acidocerinae), Zootaxa 3835 (2), pp. 251-262 : 254-257

Radicitus granitum Short & García sp. n.

( Figs. 2 , 3 B, 4B, 5, 6B, 7D, 8, 9)

Type locality. Venezuela, Bolívar State, Los Pijiguaos, 6°35.617’N, 66°49.238’W, 80 m.

Type material. Holotype <male>: “ VENEZUELA: Bolivar State/ 6°35.617’N, 66°49.238’W, 80 m / Los Pijiguaos; 16.ix.2007 / leg. A. Short, M. Garcia, L. Joly/ AS-07-015; morichal/rock outcrop” ( MIZA). Paratypes (40): VENEZUELA: Amazonas State: Tobogan de la Selva, 5°23.207’N, 67°36.922’W, 125 m, 7.i.2006, leg. A.E.Z. Short & M. García, AS-06-017 (1 ex.: SEMC); same locality but “old tobogancito”, 8.viii.2008, AS-08- 080b, (2 exs.: SEMC); same locality but 14.i.2009, “upstream slide”, leg. Short, García, Miller & Joly, VZ09-0114- 01F (1 ex.: SEMC). Bolívar State: Same data as holotype (24 exs.: SEMC, USNM, MALUZ, MIZA, NMW, NMPC); Same data as holotype but 6.viii.2008, AS-08-076 (1 ex.: SEMC); ca. 25 km E. El Burro, 6°13’4.6”N, 67°14’26.4”W, 60m, 7.viii.2008, leg. A. Short, M. García, & L. Joly, rocky morichal, AS-08-077 (1 ex.: SEMC); same locality but 12.i.2009, leg. A. Short & M. García, VZ09-0113- 01X (8 exs.: SEMC, MIZA, MALUZ); 2 km E. Rio Cuchivero, 7°29’47.3”N, 65°51’44.8”W, 45m, 6.viii.2008, leg. A. Short, M. García, & L. Joly, rock outcrop seeps, AS-08-075 (1 ex.: SEMC); rock outcrop ca. 15 km NE Pijiguaos, 6°57.904’N, 66°36.392’W, 51 m, 9.vii.2010, leg. A. Short & M. Tellez, detritus flotation, VZ10-0709-01B (1 ex.: SEMC).

Diagnosis. Size 4.5–5.0 mm. Elytra with extremely fine serial punctures, with punctures smaller than surrounding ground punctation ( Fig. 4 B). Fifth ventrite entirely pubescent. Parameres not divided into two projections ( Fig. 7 D).

The smaller size and lack of coarsely punctate elytral striae, and completely pubescent fifth ventrite will easily separate this species from both R. ayacucho and R. surinamensis .

Description. Color and punctation. Dorsum of head, pronotum and elytra very dark brown with all margins of pronotum and lateral margins of the elytra slightly paler ( Fig. 2 ). Clypeus without pale preocular patches. Thoracic and abdominal sterna and epipleura dark chestnut brown, with legs very slightly paler. Ground punctation on head and elytra moderately coarse; moderately coarse on elytral disc, and becoming extremely fine to almost obsolete laterally and posteriorly.

Head. Antennae ( Fig. 3 B) with scape c. three times as long as pedicel, antennomere 3 subequal in length as 4 and 5 combined. Maxillary palps subequal in length to the width of the anterior margin of the clypeus, with segments two and three subequal in length with apical segment slightly shorter.

Thorax. Elytra with rows of serial punctures weakly impressed along entire length ( Fig. 4 B); serial punctures subequal in size as surrounding ground punctuation, making them almost appear absent. Mesoventrite with distinctive, large laterally compressed projection, which appears as a large “tooth”; the projection strongly elevated, rising to the same plane as the ventral surface of the mesocoxae; apex of projection set with a several coarse spine-like setae. Metaventrite almost entirely pubescent, with posteromedial glabrous region represented by a narrow line in the posterior half of the metaventrite width. Metafemora with pubescence restricted to anterior third and extending distally to basal four-fifths.

Abdomen. Pubescence on ventrites 1-4 extremely fine and dense. Fifth ventrite with pubescence slightly less dense at apex, but without a glabrous patch ( Fig. 6 B). Aedeagus ( Fig. 7 D) with parameres forming a single lobe, tapering apically. Lateral margins of median lobe gradually tapering, with apex slightly shorter than parameres.

Etymology. Named after the Latin word for granite, reflecting the habitat of this species. Noun in apposition.

Distribution. This species is known from a series of localities along the northwestern edge of the Guiana Shield in Venezuela ( Fig. 8 )

Biology. This species, the most frequently encountered of the genus to date, has been found on a variety of habitats associated with streams and seeps on rock outcrops. It has been found by collecting detrital debris from seepages and floating them in pans of water ( Fig. 9 C), and also in the roots vegetation along the margins of shallow streams and seeps that are flowing over open granite (e.g. Fig. 9 A).

Figures

FIGURE 2. Radicitus granitum, dorsal, ventral, and lateral habitus (paratype).

FIGURE 3. Heads of Radicitus spp., ventral view. A) R. ayacucho, B) R. granitum.

FIGURE 4. Elytra of Radicitus spp. A) R. ayacucho, B) R. granitum.

FIGURE 6. Abdominal ventrites of Radicitus spp. A) R. ayacucho, B) R. granitum.

FIGURE 7. Aedeagi of Radicitus spp. A) R. ayacucho, B) R. surinamensis, C) R. cf. granitum (Suriname), D) R. granitum (Venezuela).

FIGURE 8. Distribution of Radicitus spp.

FIGURE 9. Habitat of Radicitus spp. in Venezuela. A) Venezuela, Bolivar State, 25 km E. El Burro (collecting event AS- 08 - 077). B) Specimen of R. granitum clinging to root mat that was pulled from the margin of the seepage shown in A. C) Venezuela: Bolivar State, 15 km NE Pijiguaos (collecting event VZ 10 - 0709 - 01 B). D) Venezuela, Amazonas State, Tobogan de la Selva (collecting event AS- 06 - 017).