Radicitus ayacucho 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 : 252-254

Radicitus ayacucho Short & García sp. n.

( Figs. 1 , 3 A, 4A, 6A, 7A, 8, 9)

Type locality. Venezuela, Amazonas State, Tobogan de la Selva, 5°23.207’N, 67°36.922’W, 125 m.

Type material. Holotype <male>: “ VENEZUELA: Amazonas State/ 5°23.207’N, 67°36.922’W, 125 m / Tobogan de la Selva; 8.viii.2008 / leg. A. Short, M. Garcia, L. Joly/ AS-08-080b; old “tobogancito””, “[barcode]/ SM0829210/ KUNHM-ENT” ( MIZA). Paratypes (36): Venezuela: Amazonas State: Same data as holotype (10 exs.: SEMC, MIZA); same data but with added habitat text: “on seepage area w/ detritus” (19 exs.: SEMC, USNM, MALUZ, MIZA, NMW, NMPC); Tobogan de la Selva, 7.i.2006, leg. A.E.Z. Short & M. García, AS-06-017 (4 exs.: SEMC). Bolívar State: 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 (3 exs.: SEMC).

Diagnosis. Size 4.7–6.2 mm. Elytra with coarse punctate striae ( Fig. 4 A). Fifth ventrite with apicomedial glabrous patch that extends anteriorly about half the width of the ventrite ( Fig. 6 A). Parameres divided into two projections medially ( Fig. 7 A).

The larger size and presence of punctate elytral striae and a glabrous patch on the fifth ventrite easily separate this species from the sympatric R. granitum . This species is externally almost identical to R. surinamensis , which possesses a larger glabrous patch on the fifth ventrite and undivided aedeagal parameres.

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. 1 ). Anterolateral margins of clypeus with faint 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 A) with scape c. three times as long as pedicel, antennomere 3 subequal in length as 4 and 5 combined. Maxillary palps slightly shorter 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 strongly impressed in posterior half and laterally; serial punctures 5-8 times larger than surrounding, extremely fine ground punctuation. Mesoventrite with distinctive, large conical projection, which is flattened on the posterior face; the projection strongly elevated, rising to the same plane as the ventral surface of the mesocoxae; apex of projection set with a few setae. Metaventrite with distinct median glabrous area that is about as wide as long; total length of glabrous patch about half the metaventrite width. Metafemora with pubescence restricted to anterior fifth and extending distally to basal four-fifths.

Abdomen. Pubescence on ventrites 1-4 extremely fine and dense. Apex of fifth ventrite with a distinct glabrous patch along medioposterior margin, which extends c. half the width of the ventrite, and spans approximately the central fifth or less of the ventrite ( Fig. 6 A). Aedeagus ( Fig. 7 A) with each paramere dividing into two lobes at midpoint, the outer lobe slightly longer than the inner one; median lobe forming a narrow projection, as long as inner paramere lobes, and expanded dorsoventrally into a plate like-structure at apex.

Etymology. Named after Puerto Ayacucho , the nearby capital of Amazonas State, Venezuela. Noun in apposition.

Distribution. Known from two localities in southern Venezuela ( Fig. 8 ).

Remarks. Most specimens have been collected along the margins of the Rio Coromoto at the “Tobogan de la Selva” site. The species occurs on both exposed granite seepages that border the creek (usually where detritus is covering the rocks) as well as in the (water saturated) roots of herbaceous plants that are growing along the margin of the creek. A few specimens were found by collecting detritus from a granite outcrop and placing it in a pan of water such that the specimens float to the surface.

Figures

FIGURE 1. Radicitus ayacucho, 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.