Hexanchorus mcdiarmidi Spangler & Staines, 2003

Maier, Crystal A., 2013, A revision of the Larainae (Coleoptera, Elmidae) of Venezuela, with description of nine new species, ZooKeys 329, pp. 33-91 : 57

Hexanchorus mcdiarmidi Spangler & Staines, 2003 Figs 4, 48, 49

For a complete description and illustrations of genitalia, see Spangler and Staines 2003.

Material examined.

VENEZUELA: Barinas State: "VENEZUELA: Barinas State; 8°03.341'N, 70°56.597'W, 203m; nr. Quiri, Rio Quiu; 15.vii.2009; leg. W. Shepard; ex. bulk sample; VZ09-0715-03Z" (99 specimens SEMC). Distrito Capital:"VENEZUELA, Dto. Federal; Los Caracas; 19 January 1985; P. Spangler, R. Faitoute; W. Steiner, & A. Conover" (6 paratypes USNM) Mérida State: "VENEZUELA: Mérida State; 8°57.205'N, 71°17.620'W, 88m; W. of Tucani; 21.vii2009; Gross sample from river; leg. Shepard; VZ09-0721-04Z" (17 specimens SEMC). Zulia State: "VENEZUELA: Zulia State; 9°50.513'N, 72°48.334'W. 252m; Perija N.P. Tukuko: Rio Tukuko; 5.vii.2009; leg. Short & Gustafson; riffle/rocks in river; VZ09-0705-01B" (96 specimens SEMC). "VENEZUELA: Zulia State; P.N. Perija: Tukuko; 18 vii.2008; Rio Marpito" "Andrew E. Z.; Short, leg." (5 specimens SEMC). "VENEZUELA: Zulia El; Tucuco (51 km S.O. de; Machiques); 24-VI-1992" "Colector:; J. Camacho" (11 specimens MALUZ).

Diagnosis.

Hexanchorus mcdiarmidi can be disinguished from all other Hexanchorus species in Venezuela by the presence of a greenish iridescent sheen on the dorsal setae (Fig. 48), the narrow parameres, and pronotum with only a shallow postero-median impression (Fig. 48).

Intraspecific variation.

This species varies slightly from black to dark brown in color, additionally, there may be slight variation in the greenish iridescence of the elytral setae. Hexanchorus mcdiarmidi has a purplish and orange iridescent sheen while submerged in alcohol (Short, pers. comm.). There is variation in size (2.9-3.4 mm TL) and slight differences in punctation among specimens.

Habitat and distribution.

Hexanchorus mcdiarmidi is widespread in lower altitude (<300 m elevation) streams throughout western Venezuela (Fig. 4). They can be found in dense aggregations on water-splashed emergent rocks in small to medium sized swift-flowing streams and rivers with rocky substrate.

Associated species.

While no other species of Hexanchorus were collected at the same localities as Hexanchorus mcdiarmidi , other laraines collected in the same habitats include Disersus dasycolus , Phanocerus congener and Phanocerus clavicornis , and Pharceonus volcanus . Other water beetles collected at the same sites include: Anacaena spp. and Enochrus spp. ( Hydrophilidae ).