Oecetis mesospina, Johanson & Malm & Sjöberg, 2022

Johanson, Kjell Arne, Malm, Tobias & Sjöberg, Tin, 2022, Description of two new species of Oecetis (Trichoptera, Leptoceridae) from Borneo, European Journal of Taxonomy 819, pp. 158-165 : 159-161

Oecetis mesospina sp. nov.

urn:lsid:zoobank.org:act:2896E944-5E55-49FB-89D5-76DF8D8E9EC2

Figs 1–5 , 11

Diagnosis

The species is distinguished from many of the Oriental and Palearctic species by the absence of modified tergites on segment VI–VIII. It resembles the Bornean Oecetis peleus Malicky, 2005 and Oecetis halirrhotios Malicky, 2005 in genitalic features, particularly in the shape of tergum X, the inferior appendages of the inferior appendages and the superior appendages. However, it is distinguished from both species by the presence of a row of short megasetae forming a comb along the mesal margin of the inferior appendages and by the phallus bearing a pair of sharply triangular lateral processes on the posterior part of the ventral side compared to rounded processes in O. peleus and O. halirrhotios . It is also distinguished from O. peleus by the more strongly curved tergum X in lateral view.

Etymology

Mesospina, referring to the row of spine-like megasetae along the mesal margin of the coxopodites.

Type material

Holotype MALAYSIA • ♂ (in alcohol); Sabah, Tawau, Maliau Basin, Nepenthes Camp , crossing stream ; 4°43′58.9″ N, 116°52′40.7″ E; 994 m a.s.l.; 9–14 Dec. 2007; B. Viklund and N. Jönsson leg.; 6 m Malaise trap, loc# VKBS-2007-27 ; DNA voucher JL5; NHRS.

Paratype MALAYSIA • 1 ♂ (in alcohol); same collection data as for holotype; DNA voucher JO7; NHRS .

Description of male

BODY. Forewing: 5.6–6.4 mm (N = 2). Tergites VI–VIII without reticulate pattern.

GENITALIA ( Figs 1–5 ). Higher than long in lateral view. In lateral view segment IX with almost straight anterior margin, dorsal and ventral parts slightly produced anteriorly and posteriorly. Acrotergite of segment IX well developed, forming single transverse wart-like aggregation of setal bases, more than three times wider than long. Pair of dorsal processes of segment IX minute, wart-like. In lateral view lower posterolateral plate of segment IX short, posteriorly rounded, situated at same level as base of inferior appendages; upper posterolateral plate of segment IX short, sharply triangular, located medially between superior appendages and inferior appendages. Longitudinal apodemes absent. Tergum X reaching as far posteriorly as inferior appendages, about twice as long as superior appendages; divided into long central and two shorter lateral processes; in lateral view, central process longer than lateral processes, curving posteroventrally, with apical megasetae, narrow in dorsal view; lateral processes curving posteroventrally, each with single, apical megaseta; in dorsal view forming triangular plates. In lateral view, superior appendages almost circular, about half as long as tergum X; in dorsal view situated closely to each other, mesally fused, almost circular. In lateral view, each inferior appendage slender along their, slightly sigmoid, parallel-sided, except narrowing apically; four very long dorsally oriented setae located at mid-length of each inferior appendage; in ventral view inferior appendages well separated after basal plate and pair of small rounded processes; each mesal plate with comb of short megasetae along mesal margin. Phallus about as long as tergum X. In lateral view almost as high as long; in ventral view anterior margin almost straight, widest anteriorly and weakly narrowing posteriorly; sharply triangular pair of lateral processes after mid-length; internal sclerite horse-shoe shaped.

Distribution

The species is only known from the type locality ( Fig. 11 ).

Figures

Figs 1–5. Oecetis mesospina sp. nov., holotype, ♂ (NHRS). 1. Genitalia, lateral view. 2. Genitalia, dorsal view. 3. Genitalia, ventral view. 4. Phallus, lateral view. 5. Phallus, ventral. Scale bar = 0.1 mm.

Fig. 11. Map with the position of the two sampling sites in Maliau Basin shown as orange dots. The position of the Maliau Basin area on Borneo is indicated with a blue rectangular in the upper-left map.