Hydrochus soekhnandanae Makhan, 2019

Perkins, Philip D., 2019, Taxonomy of Venezuelan water beetles in the genus Hydrochus Leach, 1817, and an analysis of male genitalia morphology (Coleoptera: Hydrochidae), Zootaxa 4708 (1), pp. 1-59 : 53

Hydrochus soekhnandanae Makhan , new status

Figs. 2 , 29

Hydrochus soekhnandanae Makhan 1992: 98 .

Hydrochus pupillus Orchymont : Oliva (1996: 331); misidentification.

Material examined (2): Venezuela: Sucre: VZ10-0129-04A (1 SEMC) . Monagas: VZ10-0202-03A (1 MIZA) .

Differential Diagnosis. Among Venezuelan species, recognized by the combination of small size (ca. 1.93 mm), the bright silver dorsum, the elytra with odd numbered interstriae raised, the large and very closely spaced strial punctures, the pronotum with moderately shallow depressions much more densely punctate than reliefs, the pronotal shape, the lack of black spots on the elytra, and the male genitalia ( Fig. 29 ; described below). Reliable differentiation from other similarly small sized species should include dissection of males.

Description. Habitus as illustrated ( Fig. 29 ). Size of imaged specimen (length/width, mm): body (length to elytral apices) 1.93/0.75; head width 0.50; pronotum l/w 0.45/0.50; PA 0.48; PB 0.39; elytra 1.18/0.75. Body size small (ca. 1.93 mm). Dorsum bright silver metallic, with slight bluish iridescence, elytra without black spots. Legs testaceous, with tibiofemoral joints darker. Punctation on elytra ca. 2– 4x that of pronotum. Elytra interstriae ca. 0.5– 1x strial puncture diameter. Odd numbered interstriae raised. Interstria 9 th overhanging 10 th interstria. Usual area of callus on 5 th not raised.

Pronotum slightly wider than long (as ca. 45/50), widest slightly behind anterior margin, markedly narrowed at base, sides arcuate or very slightly sinuate, smooth; anterior margin bisinuate; depressions moderately shallow, punctation much denser than on reliefs.

Elytra with spaces between strial punctures narrow ridges; apices rather sharply conjointly rounded in dorsal view, in lateral view outer margin with very slight angulation.

Ventral characters: Mentum densely, coarsely punctate, with shallow median fovea. Submentum without foveae.

Male genitalia ( Fig. 29 ) general characters: genitalia very small; parameres extending well beyond distal end of aedeagus, tips in dorsal/ventral views wide in proximal part, narrowing apically, with medial margins diverging distally, in lateral view tips arcuate toward ventrad; basal piece long, longer than parameres, slightly constricted just before base, in lateral view arcuate, orifice with rim weakly sclerotized and characteristically shaped.

Dorsal surface: adtl lacking; pdmm slightly overlapping lateral margins of aedeagus; adbl small.

Ventral surface: avtl indistinct; pvmm overlapping lateral margins of aedeagus, medial margins more widely separated than pdmm.

Remarks. Oliva (1996) synonymized Hydrochus soekhnandanae Makhan with Hydrochus pupillus Orchymont. I have examined a dissected male paratype of H. soekhnandanae , and a dissected male paratype of Hydrochus pupillus Orchymont , and conclude that they are different species. Makhan (1992) does not state where the holotype of Hydrochus soekhnandanae is deposited.

The specimen used for the images ( Fig. 29 ) is from locality VZ10-0129-04A.

Figures

FIGURE 2. Dorsal habitus of Hydrochus species.

FIGURE 29. Hydrochus soekhnandanae Makhan, habitus and male genitalia