Hydraena diffusa, Perkins, Philip D., 2011

Perkins, Philip D., 2011, New records and description of fifty-four new species of aquatic beetles in the genus Hydraena Kugelann from South America (Coleoptera: Hydraenidae), Zootaxa 3074, pp. 1-198 : 66

Hydraena diffusa , new species

Figs. 139 (habitus), 141 (aedeagus), 200 (map)

Type Material. Holotype (male): Paraguay: Dep. Concepcion, Est. San Luis, 8 ix 1997, Drechsel. Deposited in the NMW. Paratype: Same data as holotype (1 NMW).

Differential Diagnosis. This species has a well developed pronotal macula (color band ratios ca. 5/12/5), and the pronotal and elytral punctures are rather deep. It is similar in dorsal habitus to H. tucumanica Perkins and H. pantanalensis ( Figs. 74 , 85 , 139 ); differing therefrom by the larger plaques and the slightly differently shaped pronotum. Reliable determinations will require examination of the very dissimilar male genitalia of the three species ( Figs. 78, 89, 141). The aedeagus of H. diffusa is very arcuate; the drawings are made from the lateral view and the dorsal view, the latter perpendicular to the greatest plane.

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.35/0.54; head 0.22/0.36; pronotum 0.33/0.42, PA 0.37, PB 0.39; elytra 0.79/0.54. Dorsum of head piceous; pronotum testaceous in front of and behind piceous macula, ratios of color bands, as measured in midline, ca. 5/12/5; elytra brown to dark brown; legs light brown to testaceous; maxillary palpi testaceous, tip not darker.

Frons punctures ca. 1–1.5xef, larger and denser near eyes than medially; interstices laterally microreticulate, weakly shining 0.5–1xpd, medially 1–3xpd, strongly shining. Clypeus microreticulate laterally, very finely sparsely punctulate and strongly shining medially. Mentum effacedly microreticulate, very sparsely very finely punctulate, weakly shining; postmentum very finely densely micropunctulate in median concavity, surrounding areas smooth, shining. Genae raised, shining, without posterior ridge.

Pronotum weakly arcuate laterally; anterior margin straight behind eyes, emarginate behind frons, scintilla absent; punctures on disc much larger and deeper than those of frons, interstices shining, 1–3xpd, punctures larger and denser at anterior and posterior; PF1, PF2 and PF4 absent; PF3 deep.

Elytra weakly arcuate laterally; summit of posterior declivity at ca. midlength; lateral explanate margins narrow; on basal 1/3 punctures ca. 1xpd largest pronotal punctures, punctures becoming finer and more widely spaced toward posterior. Intervals not raised, shining, on basal 1/3 ca. 1–2xpd, as are interstices between punctures of a row, a few punctures subserial. Apices in dorsal aspect conjointly rounded, in posterior aspect margins forming very shallow angle with one another.

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 2/2/5/3. P1 laminate; median carina sinuate in profile. P2 l/ w ca. 2/1, sides slightly converging toward blunt apex, apex raised slightly above mesoventral intercoxal process. Plaques moderately wide, short, parallel, weakly raised, located at sides of deep median depression. Metaventrite with very short longitudinal ridge on each side, extended posteriorly from margin of each mesocoxal cavity. AIS width at straight posterior margin ca. 1.5x P2. Profemur (male) with small, sharply pointed tubercle on medial margin near trochanter. Protibia very slightly arcuate, medial margin gradually widened from base to subapically, then excavate to apex, few short setae at beginning of excavation. Mesotibia and metatibia slender, straight. Abdominal apex symmetrical; last tergite with moderately large apicomedian notch. Females not yet known.

Etymology. Named in reference to the large and yet diffuse punctures of the pronotal disc.

Distribution. Currently known only from the type locality ( Fig. 200).

Figures

FIGURE 74. Hydraena tucumanica, holotype, dorsal and lateral habitus, and venter.

FIGURE 85. Hydraena pantanalensis, holotype, dorsal and lateral habitus, and venter.

FIGURE 139. Hydraena diffusa, holotype, dorsal and lateral habitus, and venter.