Eighteen new species of Oecetis McLachlan 1877 (Trichoptera, Leptoceridae) from New Caledonia Author Johanson, Kjell Arne * kjell. arne. johanson @ nrm. se; https: // orcid. org / 0000 - 0002 - 1893 - 3429 & * kjell. arne. johanson @ nrm. se; https: // orcid. org / 0000 - 0002 - 1893 - 3429 Author Mary, Nathalie Jeanne ETHYC’O, B. P. 13821, 98 803 Nouméa Cedex, Nouvelle-Calédonie. & ethyco 2005 @ gmail. com; https: // orcid. org / 0000 - 0001 - 8250 - 7929 Author Sjöberg, Tin * kjell. arne. johanson @ nrm. se; https: // orcid. org / 0000 - 0002 - 1893 - 3429 & tin. sjoberg @ nrm. se; https: // orcid. org / 0000 - 0002 - 2813 - 9325 Author Malm, Tobias * kjell. arne. johanson @ nrm. se; https: // orcid. org / 0000 - 0002 - 1893 - 3429 & tobias. malm @ nrm. se; https: // orcid. org / 0000 - 0003 - 4610 - 4086 text Zootaxa 2020 2020-07-07 4809 2 201 240 journal article 10.11646/zootaxa.4809.2.1 1175-5326 3934048 E697983F-7223-4009-91B4-80A401D0AB8A Oecetis millei sp. nov. Figs 21–25 Diagnosis. The species is distinguished from many of the Australasian Oecetis species by the absence of modified tergites on segment VIII and forward. It resembles many other Oecetis species by having simple and slightly sigmoid or undulating coxopodites in lateral view, and having tergum X divided into a simple dorsal posterior spine and a branched bilobed main branch. It particularly resembles Oecetis loyolaensi sp. nov. and Oecetis christinae sp. nov. in the shape of the coxopodites, being slightly sigmoid in lateral view, lacking a dorsal process, and having a broad basomesal plate in ventral view. Oecetis millei sp. nov. is distinguished from both O. loyolaensi sp. nov. and O. christinae sp. nov. in that the pair of lobes of the main branch of tergum X are much shorter than the posterior spine, the upper posterolateral projection of segment IX situated on each side immediately below the superior appendages is small and triangular, and the phallus has a pair of shorter spine-like structures, not long inner spines. FIGURES 21–25. Genitalia of Oecetis millei sp. nov. , male holotype. 21 , left lateral; 22 , dorsal 23 , ventral; 24 , phallus, left lateral; 25 , phallus, ventral. Description, male. Length of each forewing 3.8–5.9 mm (N = 10). Genitalia ( Figs 21–25 ) slightly longer than tall in lateral view. Segment IX oriented almost vertically, ventral part about as long as dorsal part in lateral view; each side with anterior margin weakly convex above mid-height; posterior margin with upper and lower posterolateral processs of segment IX both short and triangular, situated immediately below superior appendage and near basal part of coxopodite, respectively; longitudinal apodeme absent; acrotergite of segment IX divided into pair of punctate warts, each about as wide as distal end of posterior spine of Tergum X in dorsal view; dorsal semimembranous processes of segment IX paired, subconical, closely situated; membranous areas absent. Main branch of tergum X forming two lobes, each about half as long as posterior spine and slightly exceeding superior appendages, semimembranous, straight, directed posteroventrad, without setae; apex narrowly blunt in lateral view; in dorsal view each lobe tapering towards cone-shaped apex, directed posterad. Posterior spine of tergum X originating from mid-length of main branch, slender, finger-like, slightly dilated apically in lateral view, narrowing along its length in dorsal view. Superior appendages short, oblong in lateral view and almost straight, in dorsal view broadly oval. Each coxopodite in lateral view slightly sigmoid-shaped, basal one-third wider than central one-third, distal onethird slender, almost straight, with rounded apex; clearly exceeding tergum X posteriorly; in ventral view with wide, large basomesal plates having mesal corners slightly produced posterad; large setae absent. Phallus shorter than coxopodites, slightly taller from one-third its length, anterior margin rounded, posteriorly with membranous tissue retracted; short inner spines weakly defined; in ventral view slightly narrower anteriorly. Male holotype : New Caledonia , Province Sud , Dumbéa River , Branche Sud , 22°08.344’S , 166°30.147’E , 42 m , 03.xi.2003 , light trap , loc#006, leg. K.A. Johanson , DNA voucher JA8 . Paratypes : 3 males : New Caledonia , Province Nord , Mont Panié , stream at camp, 20.58167°S , 164.76472°E , 1311 m , 9.xii.2003 , Malaise trap , loc#073, leg. K.A. Johanson , DNA vouchers JC1, JB9, AR7 . 2 males : New Caledonia , Province Nord , Mont Panié , stream at camp, 20.58139°S , 164.76444°E , 1310 m , 9.xii.2003 – 2.i.2004 , Malaise trap , loc#074, leg. K.A. Johanson , DNA vouchers AR3, AR4 . 3 males : New Caledonia , Province Nord , Mont Panié , 20.57306°S , 164.77139°E , 902 m , 9.xii.2003 , Malaise trap , loc#075, leg. K.A. Johanson , DNA vouchers JL7, AO4, AO5 . Etymology. The species is named millei for Dr. Christian Mille, in recognition of his work on New Caledonian Trichoptera diversity.