Hydaticus aequalis, Benetti & Gustafson & Hamada & Short, 2020

Benetti, Cesar J., Gustafson, Grey T., Hamada, Neusa & Short, Andrew Edward Z., 2020, Hydaticus aequalis sp. n. and a new record of H. devexus Trémouilles, 1996 from Brazil (Coleoptera, Dytiscidae, Hydaticini), Zootaxa 4820 (2), pp. 379-384 : 380-381

Hydaticus aequalis sp. n.

( Figs. 1A , 2A , 3 A–B, 4)

Type locality. BRAZIL: Amazonas State : Tapauá County, c. 240 km N Humaita, on BR-319 (5.503S, 62.124W) .

Type material. Holotype (♂): “ BRAZIL: Amazonas : Tapauá /-5.50298°, -62.12392°; 54 m / Humaita (c. 240 km N) on BR-319/ 11.vii.2018; leg. Short; forest/detrital pool; BR18-0712 - 01 A”, “ HOLOTYPE / Hydaticus /aequalis [red label]” ( INPA) Notes: The holotype lacks all tarsomeres on right hind-leg and all tarsomeres on left fore-leg . Paratype (♀): same labels, except margin of stream, BR 18-0712- 01 B and blue paratype label ( SEMC) .

Diagnosis. Body elongate, oval. Size large (10 mm in length). General coloration in dorsal view evenly orangish brown; head and pronotum a little lighter; elytron evenly orangish brown; thoracic ventrite and abdomen evenly orangish brown. Median lobe of aedeagus in lateral view not dorsally recurved, with straight ventral margin, basal 1/3 dorsally bulged, apical 1/6 weakly expanded with narrowly rounded apex.

Description. Habitus. Body elongate, oval, slightly attenuated posteriorly, dorsoventrally depressed; subparallel medially, widest just behind middle, lateral outline continuous in dorsal view.

Measurements. TL = 10 mm; TL-H = 9 mm; MW = 5 mm.

Coloration. General coloration in dorsal view evenly orangish brown; head and pronotum a little paler. Clypeus brown with two black spots near anterior margin; labrum yellowish brown with anterior margin darker; antenna dark yellow; palpi yellow, paler than antennae. Pronotum slightly darker on posterior margin; elytron and epipleuron evenly orangish brown. Metacoxal plates and abdomen evenly orangish brown; prosternum and metaventrite dark yellow; prosternal process with apex darker, brown. Legs dark yellow, mesotarsus, mesotibia and hind-legs little darker.

Sculpture and structure. Head with very fine punctation, coarser in basal margin; reticulation not visible at 100x. Pronotum with posterolateral angle slightly produced and rounded, posterior margin sinuate; lateral margins not margined; with very fine reticulation composed of rounded cells and fine punctuation; more impressed punctures with scattered setae on posterior margin; with some wrinkles near posterior and lateral margins. Elytron with very fine reticulation of elongate cells corresponding to about 1/3 of distance between punctures; with one row of punctures slightly impressed near suture bearing short setae; some scattered setae on lateroapical margins. Ventral surface generally smooth, without punctures and reticulation. Prosternum with large setae on lateral margins. Prosternal process convex, laterally entirely margined, with apex spatulate; with reticulation of rounded cells. Metaventral wings narrow, with anterolateral margin straight. Male protarsomeres I–III modified in a transversely oval palette with ventral adhesive setae; mesotarsomeres I–III enlarged with ventral adhesive setae. Female pro and mesotarsomeres I–III not enlarged. Protibia with stout spines on apicodorsal surface. Profemur with a row of spines on anterior surface, with fine, scattered spines on posterior margin and one row of spines basally, near trochanter. Metatarsus with reticulation composed of elongate, transversal cells in dorsal and ventral view; metatarsal claws unequal, anterior claw shorter than posterior one. Metatibia with reticulation of elongate, transversal cells; with few large punctures and spines in posterior surface; metatibial spurs acuminate apically. Metafemur with fine reticulation composed of transversal cells. Abdomen: ventrites 3–5 with a one rounded shallow depression at each side.

Male genitalia. Median lobe in dorsal view narrow; in lateral view not dorsally recurved, ventral margin straight, dorsal margin bulged in basal 1/3, weakly expanded in apical 1/6 with narrowly rounded trilobate apex.

Etymology. From the Latin Aequalis, meaning uniform, due to the more or less uniform coloration of dorsal and ventral surfaces. The name is an adjective.

Distribution. This species is only known from the type locality, in Amazonas State, Brazil ( Fig. 4 ). The site is midway along the Manaus-Humaita highway.

Habitat. The specimens were collected in the riparian corridor of a small forested stream. The holotype was taken from the margin of the stream itself, which was still flowing but largely reduced to a series of pools ( Fig. 3A ). The paratype was taken in a small isolated forest puddle that was ca. 5 m from the stream ( Fig. 3B ). Both the stream and puddle had a sand and mud substrate with abundant detritus.

Differential diagnosis. Hydaticus aequalis sp. n. is unique among Neotropical Hydaticus in having the general coloration in dorsal view almost evenly orange-brown and without elytral markings. Among the New World Hydaticus , H. aequalis sp. n. is somewhat similar to H. piceus LeConte being reddish in color and having elytra without markings, however the latter belongs to the subgenus Hydaticus (s.str.)

Figures

FIGURE 1. Habitus of Hydaticus spp. (A) H. aequalis sp. n., (B) H. devexus. Scale bars = 2.0 mm.

FIGURE 2. Median lobe of aedeagus in dorsal (left) and lateral (right) view of Hydaticus spp. (A) H. aequalis sp. n., (B) H. devexus. Scale bars = 0.5 mm.

FIGURE 3. Habitat of Hydaticus spp.: (A) Habitat of H. aequalis sp. n., collecting event BR18-0712-01B; (B) Habitat of H. aequalis sp. n., collecting event BR18-0712-01A; (C) Habitat of H. devexus, near the summit of Pico do Barbardo; red arrow indicates location of pool; (D) Vegetated pool in which H. devexus was found, collecting event BR18-0226-01A.

FIGURE 4. Known distribution of Hydaticus aequalis sp. n. and H. devexus.