Oecetis gracilis, Johanson & Mary & Sjöberg & Malm, 2020

Johanson, Kjell Arne, Mary, Nathalie Jeanne, Sjöberg, Tin & Malm, Tobias, 2020, Eighteen new species of Oecetis McLachlan 1877 (Trichoptera, Leptoceridae) from New Caledonia, Zootaxa 4809 (2), pp. 201-240 : 220-222

Oecetis gracilis sp. nov.

Figs 57–61

Diagnosis. This species is distinguished from many of the Australasian Oecetis species by the absence of modified tergites on segment VIII and forward. The species is unique in the presence of an extremely long, slender and ventrally curving posterior process of tergum X which is apically dilated in lateral view and round in dorsal view. Oecetis gracilis sp. nov. resembles O. multidentata sp. nov. in having simple and slender coxopodites and a long and curving posterior spine of tergum X. Oecetis gracilis sp. nov. can be distinguished from O. multidentata sp. nov. by having coxopodites that are tallest at mid-length instead of at their bases, a much longer and more-slender posterior spine, longer and taller superior appendages, and the long stout spine of the phallus.

Description, male. Length of each forewing 4.2–6.2 mm (N = 13). Genitalia ( Figs 57–61 ) longer than tall in lateral view. Upper two-thirds of segment IX oriented slightly posterodorsad, ventral part much longer than dorsal part in lateral view; on each side anterior margin almost straight in upper part, slightly angled at one-third distance from venter; posterior margin with long and slender lower posterolateral process of segment IX situated above base of coxopodite; upper posterolateral processes of segment IX absent; longitudinal apodemes absent; acrotergite of segment IX small, forming single cluster of punctures, about as wide as width of one superior appendage in dorsal view; dorsal semimembranous processes of segment IX long, finger-like, diverging; membranous areas absent. Main branch of tergum X forming two lateral lobes, broadly club-shaped in lateral view, each reaching as far posteriorly as superior appendages, semimembranous, almost straight along their length, directed posteroventrad, without setae; apex tall, rounded in lateral view; in dorsal view lobes almost meeting mesally, each lobe slightly narrowing posteriorly. Posterior spine of tergum X originating at base of main branch, very long, narrow for most of its length except dilating sub-apically in lateral view, gradually curving ventrad about 90° and crossing coxopodites at apex; in dorsal view slender, parallel-sided for most of its length, with circular dilated apex. Superior appendages long, about as long as main branch of tergum X, almost parallel-sided in lateral and dorsal views. Each coxopodite slender in lateral view, slightly taller at mid-length; almost straight, with almost straight apex rounded in lateral view; in ventral view coxopodites almost fused basomesally along short and broad bases, each with distal part gradually curving posteromesad and dilated in apical one-third; large setae absent. Phallus as long as coxopodites, almost tubular in lateral view; large spine originating from upper anterior part, U-shaped along right side, apex pointing left in ventral view.

Male holotype: New Caledonia, Province Sud, western slope of Mont Ningua, Kwé Néco Stream, at Camp Jacob , 3.7 km WNW summit of Mont Ningua , on Boulouparis–Thio Road , about 50 m upstream road, 21°43.613’S, 166°06.567’E, 150 m, 12.xii.2003 – 5.i.2004, Malaise trap, loc#054, leg. K.A. Johanson, DNA voucher JB1 .

Paratypes: 3 males, 3 females: same data as holotype, except DNA vouchers AR9, JD2, JC5, JH6, JC4, JF1 . 2 females: New Caledonia, Province Nord, western slope of Mont Kugüö, Xwé Wida Di Stream , 2 km E Koh, 21°35.474’S, 165°50.776’E, 154 m, 20.xi–12.xii.2003, Malaise trap, loc#036, leg. K.A. Johanson, DNA vouchers JE2, JE1 . 1 male: New Caledonia, Province Sud, Dumbéa river, Branche Sud , 22°08.344’S, 166°30.147’E, 42 m, 3.xi.2003, light trap, loc#006, leg. K.A. Johanson, DNA voucher JM9 . 1 male: New Caledonia, Province Sud, Dumbéa River, Branche Nord, 2.2 km SE summit of Mont Piditéré , 22°07.503’S, 166°29.899’E, 25 m, 21.i.2004, light trap, loc#124a, leg. K.A. Johanson & C. Pöllabauer, DNA voucher JK4 . 1 male: New Caledonia, Province Sud, western part of Plaine des lacs, 150 m downstream bridge at La Capture , 22°15.967’S, 166°49.493’E, 261 m, 4–22.xi.2003, Malaise trap, loc#007, leg. K.A. Johanson, DNA voucher JG8 . 1 male: New Caledonia, Province Sud, Tamoa River, 700 m S road RT1 between Nouméa and La Foa , 22°04.518’S, 166°16.592’E, 19.xi.2003, light trap, loc#033, leg. K.A. Johanson, DNA voucher JK8 .

Etymology. The Latin adjective g racilis means “slender,” referring to the very long and slender posterior spine of tergum X.

Figures

FIGURES 57–61. Genitalia of Oecetis gracilis sp. nov., male holotype. 57, left lateral; 58, dorsal; 59, ventral; 60, phallus, left lateral; 61, phallus, ventral.