Oxyethira (Unplaced) gyrosterna Neto & Ribeiro & Passos 2023, sp. nov.

Oxyethira (Unplaced) gyrosterna sp. nov.

(Figs 4A–4D)

Diagnosis. Oxyethira gyrosterna sp. nov. can be recognized by segment IX being round anteriorly in ventral view and by the inferior appendages being fused to each other mesally and produced into a pair of dark lobes that are parallel-sided, parallel with each other, and apically round in ventral view. This new species is similar to Oxyethira spissa Kelley 1983 by having similarly shaped segment IX and inferior appendages, but can be distinguished by characteristics of segment IX and the subgenital plate. Segment IX of the new species in dorsal view has a pair of dorsolateral processes converging mesally and tapering apically, while in O. spissa segment IX has a prominent posterolateral process with a rounded basal knob. The subgenital plate of the new species is reniform in lateral view, while in O. spissa the subgenital plate is acute and downturned.

Description. Male (in alcohol). Dark brown species. Length of each forewing 1.95 mm (holotype and paratypes; n = 3). Head unmodified, with 3 ocelli; antennae each with 34 segments terete. Tibial spur count 1-3-4. Dorsum of head with dark setae; thorax with pale yellow setae dorsally, light brown ventrally; leg segments with light brown setae. Forewings covered with fine yellow setae and small scattered patches of dark brown setae. Sternum VII with posterior mesoventral process.

Male genitalia. Segment VIII annular, with posteroventral margins produced into pair of round lobes in lateral view (Fig. 4A); in ventral view with V-shaped posteromesal incision, posterolateral margins each blunt and widely separated (Fig. 4B). Segment IX retracted in segment VIII, sternum IX produced anterad, reaching into posterior area of segment VII (Fig. 4A); in ventral view with mesal keel (Figs 4A and 4B, mk), anterior margin round, posterior margin with two pairs of slightly sclerotized, apically blunt, posterolateral processes (Fig. 4B, pp). Tergum IX produced into apicodorsal processes directed posterad (Fig. 4A, dp); in dorsal view with paired apicodorsal processes converging mesally and tapering apically (Fig. 4C, dp). Segment X membranous, fused to terga VIII and IX (Figs 4A, 4C), round apically and forming hood completely covering other genital structures in dorsal view (Fig. 4C). Subgenital plate reniform in lateral view (Fig. 4A, sg); in ventral view appearing as transverse band with lateral portions curved anterad (Figs. 4B, sg). Bilobed process consisting of pair of elongate, slender processes, each with long apical seta (Fig. 4B, bp). Inferior appendages sclerotized and slightly tapering posteriorly in lateral view (Fig. 4A, ia); in ventral view fused to each other basomesally, produced into two dark lobes that are parallel-sided, parallel with each other, and apically round in ventral view (Fig. 4B, ia). Phallus simple, elongate, apically hooked and acute (Fig. 4D); ejaculatory duct not protruding (Fig. 4D, ed).

Female, larva, pupa, and egg. Unknown.

Holotype male. BRAZIL: Pará: S„o Geraldo do Araguaia municipality, Serra das Andorinhas, Santa Cruz stream, 06°13’31.1”S / 48°26’28.1”W, 124 m, 18–31 Oct. 2019. Pennsylvania light trap, J.M.F. Ribeiro, leg. (UEMA).

Paratypes. 2 males, same data as for holotype.

Distribution: Brazil (Pará, type locality only).

Etymology. The Greek epithet “gyrosterna” refers to sternum IX, which is anteriorly round in ventral view.