Hydraena unita, 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 : 47-48

Hydraena unita , new species

Figs. 90 (habitus), 93 (aedeagus), 202 (map)

Type Material. Holotype (male): Brazil: Matto Grosso, Rio Bento Gomes (Pantanal); Flussabschnitt bei Periquito, 15° 54' S, 56° 33' W, 1 i 1993 – 30 xii 1994, E. Stuhr (31). Deposited in the NMW. Paratypes (8): Brazil: Matto Grosso, Same data as holotype (2 NMW); Paraguay: Dep. Alto Paraguay, 20 km E Aqua Dulce, 27 vii 1995, Drechsel (3 NMW); 90 km NW Bahia Negra, 30 vii 1995, Drechsel (2 NMW); Madrejon, 27 vii 1995, Drechsel (1 NMW).

Differential Diagnosis. This species is quite distinct in dorsal habitus, being densely punctate and microreticulate, lacking a pronotal macula, and having pronotal foveae PF2 confluent, forming a U-shaped impression ( Fig. 90 ). The aedeagus does not readily compare with any other described species ( Fig. 93).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.36/0.56; head 0.21/0.31; pronotum 0.34/0.43, PA 0.35, PB 0.40; elytra 0.83/0.56. Dorsum of head dark brown; pronotum, elytra and legs brown to slightly reddish brown. All specimens in type series appear to be teneral; however, there is no indication of a pronotal macula. Maxillary palpi testaceous, tip not darker.

Frons and clypeus microreticulate, dull. Frons punctures ca. 2xef, larger and denser near eyes than medially; interstices ca. 0.5–1xpd laterally, ca. 1–2xpd medially. Mentum and postmentum microreticulate, dull. Genae raised, dull, with posterior ridge laterally.

Pronotum weakly arcuate laterally; anterior margin straight behind eyes, emarginate behind frons, with median area very smooth and shining, but not produced and without distinct scintilla; punctures on disc much larger and deeper than those on frons, interstices effacedly microreticulate, weakly shining, 0.5–1xpd on disc, punctures not distinctly larger and denser at anterior and posterior; PF1 absent; PF2 moderately deep, shallow confluent medially, forming U-shaped impression; PF3 deep; PF4 shallow; PF3 and PF4 shallowly confluent.

Elytra weakly arcuate laterally; summit of posterior declivity at about midlength; lateral explanate margins moderately wide; on basal 1/3 punctures ca. 1xpd largest pronotal punctures, punctures becoming slightly smaller and more widely spaced toward posterior. Intervals not raised, effacedly microreticulate, weakly 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, rather sharply rounded, in posterior aspect margins forming shallow angle with one another.

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 1/1/4/5. P1 laminate; median carina sinuate in profile. P2 narrow, l/w ca. 4/1, sides parallel, apex blunt, apex raised slightly above mesoventral intercoxal process. Plaques weakly raised carinate lines, parallel, located at sides of deep median depression. Metaventrite with very small point on each side, extended posteriorly from margin of each mesocoxal cavity. AIS width at straight posterior margin ca. 4x P2. Protibia (male) straight, slightly widened on median margin at distal 1/3. Mesotibia slender, straight. Metatibia very slender, very slightly arcuate. Metatrochanter posterior margin angulate. Abdominal apex symmetrical; last tergite concave on each side of median longitudinal ridge, free margin sharply rounded. Female abdominal apex: last tergite broadly rounded, with shallow apicomedian emargination, ca. 18 (n=1) hooked setae, in slightly irregular row, no median gap; gonocoxite not midlongitudinally divided, apical margin sharply rounded, very weak transverse ridge evident at border of microreticulation; spermatheca not examined (poor preparation on solitary female).

Etymology. Named in reference to the united PF2 foveae of the pronotum.

Distribution. Currently known from southern Brazil and northern Paraguay ( Fig. 202).

Notes. The aedeagus of a specimen from Paraguay, 90 km NW Bahia Negra, is slightly wider than that of the holotype, and the body is also slightly wider.

Figures

FIGURE 90. Hydraena unita, holotype, dorsal and lateral habitus, and venter.