Oecetis (Oecetis) discedens, Yang & Hu & Morse, 2020

Yang, Lian-Fang, Hu, Ben-Jin & Morse, John C., 2020, Interesting new Chinese species of Leptoceridae and Odontoceridae (Insecta: Trichoptera) from several recent collecting efforts, Zootaxa 4732 (1), pp. 138-160 : 146-149

Oecetis (Oecetis) discedens sp. n. Yang & Morse

( Figs. 5 A–5D, 5F, 5H, 7A–7C)

Diagnosis. This new species belongs to the Oecetis (Oe.) lacustris Group in which the males each have short, rounded preanal appendages that are mostly or completely fused with segment X and an irregularly rounded, squat phallic apparatus with a long, curved, slender spine ( Malicky 2005). In addition, the apex of tergum X has a shallow median excision, showing similarity with Oe. (Oe.) meghadouta Schmid 1958 from southern Asia ( India, Laos, Myanmar, Philippines, Sri Lanka, Thailand, Vietnam), Oe. (Oe.) oblos Oláh 2013 from Vietnam, and holarctic Oe. (Oe.) ochracea Curtis 1825. It differs from all of the above three species by lacking a basoventral lobe of each inferior appendage in lateral or ventral views and in having the base of the phallic spine recurved in the new species (those three species having a basoventral lobe on each inferior appendage and an evenly curved phallic spine).

The female genitalia have peculiarly short, vertically erect lamellae similar to those of Oe. (Oe.) clavata Yang & Morse 2000 , from southern China, Nepal, and Thailand. The lamellae are banana shaped and nearly six times as tall as long in lateral view in the new species (lamellae have dorsal and ventral ends bulbous and are three times as tall as long in lateral view in Oecetis clavata ).

Adult. Length of each male forewing 6.5–6.7 mm (n = 3), of each female forewing 6.0– 6.2 mm (n = 2). Body entirely pale yellow. Wings hyaline, faintly yellowish, having only hint of greyish brown at all crossveins and branches of radius and medius ( Figs. 5F, 5H ).

Male genitalia. Segment IX slightly produced at center of its apicodorsal margin in dorsal view ( Fig. 5B ); paired papillae tiny, visible only in lateral view (5A upper arrow); pleura IX with large, triangular posterolateral projection on each side just above midline in lateral view ( Fig. 5A ). Preanal appendages elliptical, setose mounds, partly fused with tergum X. Tergum X having semicircular, apicomesal indentation in dorsal view ( Fig. 5B ). Inferior appendages broad in basal 1/3, gradually upcurved in lateral view ( Fig. 5A ), gradually convergent in ventral view ( Fig. 5C ); each with small basodorsal lobe at 1/3 distance from base with one erect seta extending almost to tip of appendage ( Fig. 5A lower arrow), distal 2/3 slender and tapering in lateral view ( Fig. 5A ); basoventral lobe essentially absent in lateral and ventral views; in ventral view, thickest on basal 1/3, each with smooth continuation of median edge, distal 2/3 slender and tapering with narrow tip ( Fig. 5C ). Phallus 2 times as long as deep in lateral view ( Fig. 5D ), broad and asymmetrical basally in dorsal view ( Fig. 5 D-d); paramere spine strongly recurved basally then extending backward to phallus tip, posteroventral end of phallus downcurved and narrowing to acute triangle in lateral view ( Fig. 5D ).

Female genitalia. Segment IX longitudinally short, slightly longer in ventral half, apicodorsally with tiny pair of caudal membranous papillae visible in lateral view ( Fig. 7A ), nearly hidden in dorsal view ( Fig. 7B ). Lamellae longitudinally short and vertically tall with parallel sides, nearly six times as tall as long in lateral view ( Fig. 7A ). Gonopod plate broader than long ( Fig. 7B ), with pair of posterolateral flanges in ventral view ( Fig. 7C lateral arrow), forming pair of lateroventral pockets (longitudinal grooves) in lateral and ventral views ( Figs. 7A arrow, 7C lateral arrow); internal part of gonopod VIII broadly subtriangular with acute posterior apex in ventral view ( Fig. 7C ). Spermathecal sclerite about as long as broad, subcordate, with posterolateral corners broadly rounded ( Fig. 7C mesal arrow).

Holotype male. PR CHINA: Guang-xi Province : Xi-ning City, Wu-ming District, Da-Ming-shan [Mt.], N23.496458, E108.440148, alt. 1254 m, 21–27 May 2011, Coll. Zhou S-y . Paratypes. Same data as holotype, 2 males and 2 females; same data as holotype except 200 m east of Long-teng Hotel N23.495801, E108.438620, alt. 1202 m, 09 Aug. 2011, Coll. Song H-t .

Etymology. Latin, discedens , adjective, meaning “separated,” referring to the apex of male tergum X with a semicircular indentation separating a pair of apices in dorsal view.

Distribution. Found only at the type localities, Oriental Region, Southeast China.

Figures

FIGURE 5. Oecetis (O.) discedens Yang & Morse, sp. n., male. 5A–5D, genitalia: 5A, left lateral; 5B, dorsal; 5C, ventral; 5D, phallus, left lateral; 5D-d, phallus, dorsal. 5F, Right forewing, dorsal. 5H, Right hind wing, dorsal.

FIGURE 7. Oecetis spp. n., female genitalia. 7A–7C, Oecetis (O.) discedens Yang & Morse, sp. n.: 7A, left lateral; 7B, dorsal; 7C, ventral. 7D, 7F, Oecetis (Pleurograpta) spinellosa Yang & Hu, sp. n.: 7D, left lateral; 7F, ventral.