Hydraena takutu, 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 : 20-21

Hydraena takutu , new species

Figs. 17 (habitus), 20 (aedeagus), 194 (map)

Type Material. Holotype (male): Guyana: Mazaruni-Potaro, Takutu Mountains, berlese of leaf packs from rocky shaded stream, 6° 15' N, 59° 5' W, 18 xii 1983, P. D. Perkins & P. J. Spangler. Deposited in the MCZ. Paratypes: Same data as holotype (7 MCZ).

Differential Diagnosis. Similar in dorsal habitus to H. curvosa and H. hintoni ( Figs. 16–18 ); differentiated from both species by the non-carinate metaventral plaques, and the smaller size (ca. 1.48 mm vs. 1.58–1.76 mm). H. takutu is additionally differentiated from H. hintoni by the differently shaped posterior part of the pronotum, and from H. curvosa by the differently shaped anterior part of the pronotum. The aedeagi of the three species, while having a basic plan similarity, markedly differ in many details ( Figs. 15, 19–20).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.48/0.67; head 0.25/0.36; pronotum 0.34/0.46, PA 0.38, PB 0.37; elytra 0.90/0.67. Dorsum of head with frons dark brown to piceous, clypeus brown; pronotum dark brown except disc slightly darker; elytra and legs dark brown; maxillary palpi testaceous, tip not darker.

Frons punctures ca. 1–1.5xef, larger and denser near eyes than medially; interstices microreticulate laterally, 0.5–1xpd, shining, 3–5xpd medially. Clypeus very finely sparsely punctate, each puncture with moderately long, recumbent seta. Mentum and postmentum very sparsely very finely punctulate, shining. Genae raised, shining, with very shallow transverse impression, but without posterior ridge.

Pronotum subcordiform, sides sinuate both in front of and behind arcuate middle, not turning outward basally, posterior angles right; anterior margin straight behind eyes, rather markedly emarginate behind frons, scintilla absent; punctures on disc much larger and deeper than those of frons, interstices shining, 0.5–3xpd, punctures larger and denser at anterior and posterior; PF1 and PF2 absent; PF3 and PF4 deep, shallowly confluent; indistinct low ridge between PF3 and lateral margin.

Elytra appearing humped, very convex at summit of posterior declivity, slightly before midlength; lateral explanate margins wide; on basal 1/3 punctures ca. 1xpd largest pronotal punctures, punctures becoming finer and much more widely spaced toward posterior. Intervals not raised, shining, on basal 1/3 ca. 0.5–2xpd, as are interstices between punctures of a row, a few punctures subserial. Apices in dorsal aspect weakly separately rounded, in posterior aspect margins forming very shallow angle with one another.

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 4/1.5/7/6. P1 not laminate, ca. 3/4 width of P2; median carina sinuate in profile. P2 l/w ca. 3/2, sides slightly converging toward blunt apex, apex at same level as mesoventral intercoxal process. Plaques moderately narrow, very slightly arcuate, slightly converging toward one another anteriorly, weakly raised, located at sides of deep median depression, each plaque widest near midlength, tapering anteriorly and posteriorly. Metaventrite with short, low, midlongitudinal ridge between mesoventral intercoxal process and median depression. Metaventrite also with very short longitudinal ridge on each side, extended posteriorly from margin of each mesocoxal cavity. AIS and adjacent area on first ventrite conjointly forming shallow concavity; AIS width at straight posterior margin ca. 1.5x P2. Protibia slender, straight. Mesotibia very slightly arcuate. Metatibia slender, straight, medial margin with row of short setae in distal 1/2. Male abdominal apex symmetrical. Female abdominal apex: last tergite broadly rounded, without apicomedian notch, ca. 28 (n=1) slightly hooked, long setae each of which are widest at about midlength, taper slightly in both directions, and rather sharply pointed at tip; gonocoxite divided by weakly sclerotized midlongitudinal area, apical margin broadly rounded, lacking transverse ridge.

Etymology. Named in reference to the type locality.

Distribution. Currently known only from the type locality ( Fig. 194 ).

Figures

FIGURE 16. Hydraena curvosa, holotype, dorsal and lateral habitus, and venter.

FIGURE 17. Hydraena takutu, holotype, dorsal and lateral habitus, and venter.

FIGURE 18. Hydraena hintoni, holotype, dorsal and lateral habitus, and venter.

FIGURES 193 – 194. 193. Geographical distributions of species in the Paeminosa Group. 194. Geographical distributions of species in the Curvosa and Multispina Groups.