Hydrochus biexcavatus Perkins 2021, new species
Creators: name: Perkins, Philip D.
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Hydrochidae
Hydrochus
Hydrochus biexcavatus

description: Hydrochus biexcavatus, new species
Figs. 1, 5, 29
Type material. Holotype (male): “ Mexico: Prov. Campeche, 10 km S Campeche, 50 m, 13.7.2008, leg. Wewalka (Mex 10)” (NMW). Paratypes (123): Belize: Cayo District, San Igmacio (8 km S); stock pond, 23.v.1986, leg. Paul J Spangler & Robiin A. Faitoute (16) (29 NMNH). Costa Rica: 10 mi. NW Liberia, 25.vii.1965, leg. Paul J. Spangler (1 NMNH); 16 m. S. La Cruz, 13.vii.1965, leg. Paul J. Spangler (1 NMNH); 5 mi. SW Liberia, 24.vii.1965, leg. Paul J. Spangler (17 NMNH); Santa Cruz, 21.vii.1962, leg. no collector on label (24 NMNH); Alajuela, Cano Negro, 24.viii.1998, leg. Drechsel (1 NMW); Guanacaste, 15 km SE Canas, Hacienda Tagoba, 23.iii.1965, leg. P. Cook (1 CAS); 18.7 km NW Bagaces, Hwy 1, Rio Carana, (10°39’N, 85°22’W), 4.vi.1973, leg. Erwin & Hevel (1 NMNH); F.N. Barra Honda, pond and outflow stream, elev. 61 m, 27.xi.2002, leg. W. Shepard (3 SEMC); Nandayure; Barra Honda N.P., Lake at trailhead, elev. 61 m (10°10’51’’N, 85°19’47’’W), 27.vi.2002, leg. W. Shepard & R. Roughley (6 SEMC); Palo Verde Biol. Station, ex. blacklite, 4.vi.1993, leg. Steve Lingafelter (2 SEMC); Palo Verde N.P.: nr. Birding tower; lagoon margin, 11.i.2004, leg. AEZShort & DJLebbin (AS-04-030a) (1 SEMC); Rd to Palo Verde; 11.4 km past Rt. 1; roadside ditch, elev. 35 m, 11.i.2004, leg. AEZShort & DJLebbin (AS-04-027) (2 SEMC); Heredia, La Selva (3 km S Puerto Viejo), at UV blacklight in station nr. 2nd forest, elev. 80 m (10°25’N, 84°0’W), 1.vi.1996, leg. R. S. Hanley (RSHCR012) (1 NMW); Puntarenas, Qu. Negra, ca. 8 km NW Golfito nr. La Gamba (vill.), at Field Station La Gamba, elev. 90 m (8°42’6’’N, 83°12’7’’W), 1-3.iii.2009, leg. M. Brojer (1 NMW). Honduras: Casas Viejas, 20.v.1966, leg. J. M. Matta (1 FSCA). Mexico: Campeche, 10 km S Campeche, elev. 50 m, 13.vii.2008, leg. Wewalka (Mex 10) (7 NMW); Michoacan, Patzcuaro, 7.vii.1964, leg. P.J. Spangler (6 NMNH); San Luis Potosi, 14 miles East C. del Maiz, 19.xi.1948, leg. H. B. Leech (1 CAS); El Naranjo, 3.i.1950, leg. L. D. Beamer (3 SEMC); Tamazunchale, (21°16’N, 98°48’W), 2.i.1985, leg. James Adams (1 SEMC); Veracruz, 9 mi. W. Poza Rica, 27.viii.1965, leg. Paul J. Spangler (6 NMNH); Sayula de Alemán, Almagres, 2.xii.1998, A. Gómez col. (1 IEXA). Nicaragua: Puerto Cabezas, 1-30.vii.1971, leg. J. Maldonado C. (2 NMNH); Rio San Juan, Rio San Juan, Refugio Bartola, (10°59’N, 84°20’W), 5-10.viii.2002, leg. W. D. Shepard (2 SEMC); Rivas, Rio Ochomogo, in Ochomogo at Paso Real de Ochomogo, elev. 60 m (11°39’25.69’’N, 85°58’15.01’’W), 13.ii.2013, leg. M. Brojer (2 NMW).
Differential diagnosis. Among Central American species, recognized by the combination of moderate size (ca. 3.20 mm), the moderately low and relatively impunctate pronotal reliefs, the dull, minutely roughened dorsum, and the male genitalia (Fig. 5; described below). This species has a generalized Hydrochus habitus; reliable determinations will require dissection of males. Differences of the male genitalia from that of the somewhat superficially similar H. vagus include, in H. biexcavatus, the wider aedeagus with a much larger distal membranous area, the differently shaped dorsal margin of the aedeagus, the larger and differently shaped adbl, the more widely separated pdmm, and the differently shaped paramere tips, each with excavate dorsal surface (Figs. 5, 16). Differences of the male genitalia from that of the somewhat superficially similar H. vanvondeli include, in H. biexcavatus, the wider aedeagus with a larger distal membranous area and having the agw nearer the aedeagal base, the longer aedeagus, compared to the length of the parameres, the aedeagus tip extending beyond the level of the plsa (in H. vanvondeli the tip only attains the same level as the plsa), the larger and differently shaped adbl, and the differently shaped paramere tips, each with excavate dorsal surface (Figs. 5, 23).
Description. Habitus as illustrated (Fig. 5). Size: holotype (length/width, mm): body (length to elytral apices) 3.17/1.10; head width 0.73; pronotum l/w 0.83/0.73; PA 0.68; PB 0.61; elytra 2.05/1.10. Body size moderately large (ca. 3.17 mm). Dorsum golden brown, with very little iridescence, cuticle minutely roughened, dull, elytra without black spots. Punctation on elytra ca. 2–3x that of pronotum. Elytra interstriae ca. 0.5–1× strial puncture diameter. Interstria 9 th more convex than others, overhanging 10 th interstria. Usual area of callus on 5 th moderately raised, moderately elongate, ca. 5 punctures in row on each side.
Pronotum slightly wider than long, widest slightly behind anterior margin, narrowed at base, sides arcuate, minutely denticulate; anterior margin bisinuate; densely moderately coarsely punctate, except less dense on reliefs; depressions deep.
Elytra with spaces between strial punctures ca. 0.5–1x their diameter; apices rather sharply conjointly rounded in dorsal view, in lateral view outer margin with slight angulation.
Ventral characters: Mentum coarsely densely punctate, with large median fovea. Submentum with two small foveae. Legs testaceous, femora and tibiofemoral joints slightly darker than tibiae.
Male genitalia (Fig. 5) general characters: paramere tips slender and pointed, narrower in lateral view than in dorsal/ventral views, in dorsal/ventral views with medial margins at apex parallel or nearly so, then arcuate away from midline, immediately proximal to plsa with dorsal surface excavate; aedeagus in dorsal/ventral views lanceolate, widest slightly proximal to midlength; in lateral view slightly narrower in distal ½, and wider in proximal 1/2, with dorsal margin slightly undulating; lateral margins of aedeagus sclerotized; basal piece length equal to or very slightly shorter than parameres, tapering slightly from distal to proximal, orifice strongly sclerotized.
Dorsal surface: pdmm widely separated, overlapping aedeagus only near base; adbl large; adtl at about midlength; each paramere with small excavation just proximal to psla, paramere tips without sclerotized ridge.
Ventral surface: pvmm approximating lateral margin of aedeagus, except overlapping basally; avtl very near base of aedeagus.
Etymology. Named in reference to the excavations of the male genitalia paramere tips.
description: Published as part of Perkins, Philip D., 2021, Taxonomy of Central American water beetles in the genus Hydrochus Leach, 1817 (Coleoptera: Hydrochidae), pp. 459-503 in Zootaxa 4974 (3) on pages 466-467, DOI: 10.11646/zootaxa.4974.3.2, http://zenodo.org/record/4777839