Metrichia elongata Carvalho & Moreno & Desidério & Pes & Hamada 2024, sp. nov.

Metrichia elongata sp. nov.

(Figs 2A–2D, 3A–3H)

Material examined. Holotype male (INPA-TRI 000139) (INPA). BRAZIL: Tocantins: Palmas, Parque Estadual do Lajeado, Igarapé da Onça (#01-TO), 10°06’44.50”S, 48°15’31.10”W, el. 596 m a.s.l., 18.i.2018, G.A. Gusmão, J. O. Silva, R. Santos legs., Malaise trap.

Paratype: Same data as holotype, 1 male (INPA-TRI 000140) (INPA).

Diagnosis. This new species can be easily recognized by the shape of the dorsolateral hooks in lateral view, each boomerang-shaped basally with its dorsal branch longer than its ventral branch and both apices slender; the inferior appendages are subrectangular and elongate in lateral view, with truncate apices and, in dorsal and ventral views, with inner surfaces covered by numerous setae; and the phallus has two stout subapical spines and its apex is subtruncate, strongly sclerotized.

Description. Adult male. Forewing length 1.83–1.89 (n = 2). General color (in alcohol) dark brown (Fig. 2A). Head without modifications, with three ocelli; dorsally with two pairs of setal warts; ocellar pair appressed on midline, each subtriangular; occipital pair large, ellipsoid (Fig. 2B). Antennae unmodified (Fig. 2A). Maxillary palpi each 5-articulated; labial palpi 3-articulated. Mesoscutellum broadly subtriangular and with transverse suture (Fig. 2A). Forewings each with forks I, II, III; R 1 and discoidal cell absent; fork I originating near middle of wing; basal 1/2 of R 3 fused with basal 1/2 of R 4+5 before fork II; M 1+2 fused to R 4+5 for short distance and then separate to apex; fork of M 1+2 and M 3+4 veins distant of origin of fork I; r and r-m crossveins absent (Fig. 2C). Hind wings each with forks III and V; C with row of short spines on proximal region; R 2+3 vein originating before level of apex of M 1+2; base of M 1+2 vein fused with R 2–5, becoming independent from 1/2 of R 2–5; Cu 1 vein subdivided apically into 2 branches (Fig. 2D). Tibial spur formula 1, 3, 4. Abdomen without modifications. Sternum VII with small ventromesal process. Segment VIII shorter ventrally than dorsally (Fig. 3G).

Male genitalia. Segment IX, in lateral view, with upper anterolateral margins slightly concave and lower anterolateral margins projecting anterad and rounded; upper posterolateral margins rounded (Fig. 3A); in dorsal view, with membranous, slightly rounded posterior margin (Fig. 3C); in ventral view, round anteriorly and concave posteriorly (Fig. 3D). Preanal appendages, in dorsal view, short, about 1/7 as long as inferior appendages, apices rounded; each with about eight stout, long dorsal setae (Figs 3A, 3C; only three shown, others represented by their alveoli). Pair of dorsolateral hooks medium-sized, almost half as long as inferior appendages; each with base, in lateral view, boomerang-shaped, with dorsal branch longer than ventral branch and extending posterad, its apex slender, slightly curved ventrad (Fig. 3B). Subgenital plate absent. Tergum X semi-membranous; apex convex (Fig. 3C). Inferior appendages, in lateral view, subrectangular; about 2X as long as wide; basodorsal margin without lobe; ventral margin longer and slightly convex, each inferior appendage tapering toward obliquely truncate apex (Figs 3A, 3G); in dorsal and ventral views, with mesal surface bearing numerous short, fine, spine-like setae covering entire region, longitudinal row of medium-sized setae basoventrally and cluster of long setae subapically (Figs 3C, 3D, 3H). Phallus tubular, elongate, slightly constricted mesally; with two stout subapical spines: one large spine curved transversally, and one medium-size spine curved ventrad (Figs 3E, 3F); apex subtruncate, strongly sclerotized; ejaculatory duct sclerotized, slightly sinuous, and protruding apically (Fig. 3E).

Distribution. BRAZIL: Cerrado biome (Tocantins State) (Fig. 1).

Etymology. The species name is a Latin adjective and refers to the elongate shape of the inferior appendages, in lateral view.

Remarks. The new species resembles M. avon Bueno-Soria 1983 from Costa Rica, Mexico, and Panama by the rectangular and apically truncate shape of the inferior appendages. However, in M. elongata sp. nov. sternum IX is about half as long as the inferior appendages in lateral view, but longer in M. avon. In addition, the mesal surfaces of the inferior appendages in the new species are entirely covered by numerous short, fine, spine-like setae, whereas the setae are long, stout, and located on the ventromesal margin in M. avon.

Five species groups are recognized in Metrichia, which are defined by the characters of the male abdominal segments, including the sacs and especially the genital structures (Flint 1972; Bueno-Soria & Holzenthal 2003). Most Metrichia species are included in these groups, but slightly less than half have not been assigned to any species group, sometimes because their characters do not correspond with those defined for these groups (Bueno-Soria & Holzenthal 2003; Desidério et al. 2023a). Metrichia elongata sp. nov. is tentatively assigned to the M. aberrans Group of Flint (1972) based on the absence of pouches on abdominal segments and the phallus having two spines apically. This assignment is tentative because it shares characters of the inferior appendages (e.g., numerous spines or peg-like setae covering the entire mesal surface) with some species mainly from Central American and, as mentioned by Desidério et al. (2023a), may constitute new groups.

The possible presence of hamuli (hooked setae) on the costal margins of the hind wings suggests that this species and those described by Desidério et al. (2023a) may employ wing coupling, the uniting of wings to serve as single airfoils in flight. If so, this would be the first suspected occurrence of wing coupling in Hydroptilidae or in any of the other basal lineages of Integripalpia (Stocks 2010a, 2010b).