Hydrochus obscurus Sharp 1882
Creators: name: Perkins, Philip D.
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Hydrochidae
Hydrochus
Hydrochus obscurus

description: Hydrochus obscurus Sharp, 1882
(Figs 1, 4, 8)
Hydrochus obscurus Sharp, 1882: 90.
Hydrochus vanbergehenegouweni Makhan, 1992 (synonymized by OĿıඏA 1996)
Type material examined. LൾǤŦƟŦYPൾ (hereby designated): male (NHM): ‘ Hydrochus obscurus D. S. Paso Antonio. Guatemala.Champion [written on specimen card] // [male symbol] // LECTOTYPE [blue disc] // Paso Antonio, 400 ft. Champion.// B.C.A. Col. I. 2. Hydrochus obscurus Sharp. // HABITUS/GENIT. DIGITAL IMAGES captured 2020 P.D. Perkins // [red] LECTOTYPE Hydrochus obscurus Sharp desig. P. D. Perkins.ʼ. PARAĿൾǤŦƟŦYPൾඌ: 2 females (NHM): label data same as lectotype, except with blue paralectotype labels, and yellow labels: ‘ PARALECTOTYPE // Hydrochus obscurus Sharp // desig. P. D. Perkinsʼ.
Additional material examined (26 spec.): GƲAŦFMAĿA: Izabal, 1 mi. N. Morales. Km 239 Atlantic Hwy, 16-18.viii.1965, leg. Paul J. Spangler (2 NMNH); 20 mi. SW Puerto Barrios, 16.viii.1965, leg. Paul J. Spangler (5 NMNH); 28 mi. SW Puerto Barrios, 16.viii.1965, leg. Paul J. Spangler (18: NMNH); Quirigua, 14.viii.1965, leg. P. J. Spangler (1: NMNH).
Lectotype designation. The NHM kindly provided three syntypes of Hydrochus obscurus, which are part of the Sharp Biologia Centrali-Americana types collection. The syntypes consist of one male and two females, all from Paso Antonio, Guatemala. I have selected the male to serve as lectotype and labeled it as such, and provide images of the habitus, male genitalia, and labels of that specimen (Figs 1, 4, 8). The other syntypes have been labeled paralectotypes. One of the syntypes bears a lectotype label by J. L. Hellman, but this designation was never published. This label has been reversed and ‘unpub.ʼ written on the reverse side.
Differential diagnosis. Among Guatemalan species, H. obscurus is recognized by the combination of moderate size (ca. 2.69–3.23 mm), the moderately low and relatively impunctate pronotal reliefs, and the male genitalia (Fig. 4). This species has a generalized Hydrochus habitus; reliable determinations will require dissection of males. The parameres are slightly spread in the lectotype; see H. obscurus genitalia figure in PൾRĸıNඌ (2019b) for non-spread condition.
Redescription. Habitus as illustrated in Fig. 4. Size of lectotype (in mm): body (length to elytral apices / width) 2.92 / 0.98; head width 0.69; pronotum length / width 0.63 / 0.67; PA 0.63; PB 0.58; elytra length / width 1.81 / 0.98. Body size moderate (ca. 2.69–3.23 mm in Guatemalan specimens). Dorsum grey, with slight to moderately strong iridescence, elytra with diffuse dark grey to black spots. Legs testaceous, with tibiofemoral joints darker. Punctation on elytra ca. 2–3× that of pronotum. Elytra interstriae ca. 1.0–1.5× strial puncture diameter. Interstria 9 th more convex than others, overhanging 10 th interstria. Callus on 5 th interstria in usual location, moderately raised, moderately elongate.
Pronotum length and width equal, or only very slightly wider than long, widest slightly behind anterior margin, narrowed at base, sides arcuate or very weakly sinuate, smooth; anterior margin slightly bisinuate; depressions deep to moderately deep, much more densely punctate than low reliefs between depressions, latter almost entirely impunctate.
Elytra with spaces between strial punctures ca. 0.5–1.0× their diameter; apices rather sharply conjointly rounded in dorsal view, in lateral view outer margin with slight angulation.
Ventral characters: Mentum coarsely punctate, with median fovea. Submentum with two foveae.
Male genitalia (Fig. 4). General characters: paramere tips in dorsal/ventral views very weakly sagittate, lateral margins between plsa and distal end very slightly emarginate, medial margins arcuate toward midline, in lateral view tips narrow and tapering; aedeagus basically lanceolate shaped, agw slightly before midlength; basal piece slightly shorter than parameres, with orifice sclerotized rim produced in small projection on apicoventral margin.
Dorsal surface: adtl at about distal third; adbl small; pdmm overlapping alm basally.
Ventral surface: avtl at about proximal third; pvmm closely approximating aedeagus lateral margins.
Remarks. I have examined the holotype of Hydrochus vanbergehenegouweni from Venezuela, including the male genitalia. I concur with OĿıඏA (1996) that Hydrochus vanbergehenegouweni is conspecific with Hydrochus obscurus.
description: Published as part of Perkins, Philip D., 2020, Taxonomy of Guatemalan water beetles in the genus Hydrochus (Coleoptera: Hydrochidae), pp. 291-301 in Acta Entomologica Musei Nationalis Pragae 60 (1) on pages 295-297, DOI: 10.37520/aemnp.2020.016, http://zenodo.org/record/3879760