Taxonomic notes on Nemoura banatica Kis, 1965 and Nemoura marginata Pictet, 1836 (Plecoptera: Nemouridae) from the Jura Mountains

Originally described from the Banat region, which is presently divided between Hungary, Romania and Serbia, Nemoura banatica Kis, 1965 had been considered as a synonym of Nemoura marginata Pictet, 1836 ever since the study of Zwick (1970), but was recently reinstated as a valid species by Vinçon et al. (2024) after the discovery of this species in several headwater regions in Austria, Italy, Slovenia, and the Jura Mountains of France and Switzerland.For establishing the synonymy, Zwick (1970) had relied on microscopic preparations of the apical sclerite of the epiproct of adult males (Fig. 9), which have become the standard method of taxonomic studies of Nemoura.By placing side-by-side fresh microscopic preparations of N. banatica (Figs 123) and N. marginata (Figs 456) from the Jura Mountains, it appears that the drawings of the apical sclerite of N. marginata provided by Zwick (1970, his Fig. 1m) show characteristics that are somewhat intermediate between both species (Fig. 9).The tip of the apical sclerite of N. marginata, as drawn by Zwick (Fig. 9), is less protruding than it is in freshly prepared specimens (Figs 4-6, 8) and thus appears close to N. banatica (Figs 1-3, 7), which might explain why Zwick (1970) could consider the latter as being a synonym of N. marginata.Given the succinct original description of N. marginata by Pictet (1836, pg.181), as well as the absence of type material, Zwick (1970) had undertaken to designate a neotype based on a specimen collected in May 1943 from River Flon, located on the foothills of the Jura Mountains in the Lausanne region, though the original description of Pictet (1836, pg.182) reports the species from the "Vallée de Chamounix [i.e.Chamonix]" and from the Salève region (Pictet 1841, pg.398), both located in the Savoy Prealps.In defense of Zwick (1970) it may be invoked that the neotype for N. marginata chosen by this author had been based on older material preserved in ethanol, with subsided epiprocts.Specimens from this same locality (05.07.1942,River Flon near Lausanne, leg.Jacques Aubert, GBIFCH01219423) are still extant in the collections of the MZL (State Museum of Natural Sciences (Naturéum), Department of Zoology, Lausanne, Switzerland) and can be identified morphologically by the present author as corresponding to N. marginata.However, having been collected > 80 years ago, the apical sclerite of the epiproct of these specimens is also far less protruding than it is in fresh specimens (Fig. 8) and looks close to the one of N. banatica (Fig. 7).It should be noted that microscopic preparations of the apical sclerite of the epiproct of adult males of N. marginata are very delicate to perform, given that care must be taken not to crush or dislocate this small sclerite, which is attached perpendicularly to its base (Figs 78).It is recommended to first soak the abdomen of specimens preserved in ethanol overnight in 10% room-temperature NaOH before separating and cleaning the epiproct with a dissection needle (Figs 3, 6).The cleaned structures can then be prepared as microscope slides and are best studied by phase-contrast microscopy (Figs 1-2, 4-5).In some figures of N. marginata found in the literature, this apical sclerite is compressed, making the tip of the sclerite nearly invisible.The illustrations of N. marginata, found in Koese (2008), represent an intact tip (his figs 151, 161), whereas the tip of the left apical sclerite is compressed (his fig.160).The microscopic preparation of N. marginata found in Enting (2003, his Fig. 14) also shows a crushed apical sclerite, provided that it is not a misidentified specimen of Nemoura erratica Claassen, 1936.The problem arising from incorrectly prepared samples is that the differences between N. banatica and N. marginata become blurred.The distal edge of the apical sclerite of the epiproct of N. marginata has a long, arched lateral extension ending in a well-marked blunt tip (Figs 4-6, 8), whereas this tip is much less prominent in N. banatica (Figs 1-3, 7).In macroscopic view, the separation of adult males of N. marginata and N. banatica from the Jura Mountains is possible only with specimens having well sclerotized cerci and epiprocts.In dorsal and ventral view, the membranous part of the tip of the cercus of N. banatica is long and distinctly swollen and the sclerotization of the cercus does not reach to its apex (Fig. 10).On N. marginata, in contrast, the membranous part is shorter, straight, and narrow, and the sclerotization