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 variabilis sp. nov. Figs 83–87 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 similar to several species distributed in Australasia. The coxopodite of O. variabilis sp. nov. resembles those of O. chathamensis Tillyard 1925 , from the New Zealand Chatham islands , but they also appear similar to those of the Australian O. umbra Neboiss 1977 , O. magelensis Wells 2006 , and O. crosslandi Wells 2004 . Oecetis variabilis sp. nov. is separated from these species in its shorter posterior spine of tergum X, the shape of the basoventral process of each coxopodite, and the very broad phallus. Description, male. Length of each forewing: 7.3 mm (N = 1). Genitalia ( Figs 83–87 ) slightly longer than tall in lateral view. Segment IX oriented vertically, narrowly drop-shaped in lateral view, ventral part much longer than dorsal part; in lateral view each side with anterior margin weakly convex; ventral half of posterior margin with tall, short, rounded lower posterolateral process of segment IX; upper posterolateral process of segment IX triangular, situated immediately below superior appendages; longitudinal apodeme located evident anteriorly (but not posteriorly) as continuation of lower margin of coxopodite; acrotergite of segment IX forming single uniform cluster of punctures, about as wide as distance between superior appendages in dorsal view; dorsal pair of semimembranous processes of segment IX short, posteriorly oriented lobes situated closely to each other; membranous areas absent. Main branch of tergum X forming pair of semimembranous lobes, about twice as long as superior appendages, oriented posteriorly and curving slightly ventrad near apex, apex with two long setae; in dorsal view well separated from half-length, oriented posteriorly. Posterior spine of tergum X originating basally on main branch, slightly longer than superior appendages, almost straight, oriented posteriorly; in lateral view slender along its length, basally wide in dorsal view before narrowing at mid-point. Superior appendages about half as long as main branch of tergum X, oblong-rectangular in lateral view; oval in dorsal view. Pair of coxopodites each forming tall plate for basal half, sharply narrowing at mid-length into slender process originating from lower edge; ventral process originating basally, immediately posterior of segment IX; asymmetrical with left and right ventral processes of different length. Phallus about as long as coxopodites, almost parallel-sided in lateral view, almost round (onion-shaped) in ventral view; long sclerotized spine originating from right-dorsal part of anterior end, curving ventrad and to left before sharply angling to the right before posterior end; short second sclerotized process located dorsally near posterior end. FIGURES 83–87. Genitalia of Oecetis variabilis sp. nov. , male holotype. 83 , left lateral; 84 , dorsal; 85 , ventral; 86 , phallus, left lateral; 87 , phallus, ventral. Male holotype : New Caledonia , Province Nord , Wan Pwé On Stream , draining NNE side of Mont Panié , 3.9 km NW Cascade de Tao , 20°31.820’S , 164°47.016’E , 18.xii.2003 , light trap , loc#085, leg. K.A. Johanson , DNA voucher JK1 . Etymology. The Latin adjective variabilis , means “variable,” referring to the shape of the ventral processes of the coxopodites in ventral view.