Croatian mayfies (Insecta, Ephemeroptera): species diversity and distribution patterns 99 Croatian mayflies (Insecta, Ephemeroptera): species diversity and distribution patterns Marina Vilenica 1,3 , Jean-Luc Gattolliat 2 , Zlatko Mihaljević 3 , Michel Sartori 2 1 University of Zagreb, Faculty of Teacher Education, Petrinja, Croatia 2 Museum of Zoology, Lausanne, Switzerland 3 University of Zagreb, Faculty of Science, Department of Biology, Division of Zoology, Zagreb, Croatia Corresponding author: Marina Vilenica (marina.vilenica@gmail.com) Academic editor: Benjamin Price  |  Received 26 June 2014  |  Accepted 26 August 2015  |  Published 28 September 2015 http://zoobank.org/13A6BA91-B9A6-4B77-81E6-E43F07B58C00 Citation: Vilenica M, Gattolliat J-L, Mihaljević Z, Sartori M (2015) Croatian mayfies (Insecta, Ephemeroptera): species diversity and distribution patterns. ZooKeys 523: 99–127. doi: 10.3897/zookeys.523.6100 Abstract Knowledge of the mayfy biodiversity in the Balkan Peninsula is still far from complete. Compared to the neighbouring countries, the mayfy fauna in Croatia is very poorly known. Situated at the crossroads of central and Mediterranean Europe and the Balkan Peninsula, Croatia is divided into two ecoregions: Dinaric western Balkan and Pannonian lowland. Mayfies were sampled between 2003 and 2013 at 171 sites, and a total of 66 species was recorded. Combined with the literature data, the Croatian mayfy fauna reached a total of 79 taxa. Of these, 29 species were recorded for the frst time in Croatia while 15 spe- cies were not previously recorded in Dinaric western Balkan ecoregion. Based on the mayfy assemblage, sampling sites were frst structured by ecoregion and then by habitat type. In comparison with the sur- rounding countries, the Croatian mayfy fauna is the most similar to the Hungarian and Bosnian fauna. Some morphologically interesting taxa such as Baetis cf. nubecularis Eaton, 1898 and Rhithrogena from the diaphana group were recorded. Ephemera cf. parnassiana Demoulin, 1958, the species previously recorded only from Greece, was also recorded. Keywords Ephemeroptera, species list, biodiversity, Balkan Peninsula ZooKeys 523: 99–127 (2015) doi: 10.3897/zookeys.523.6100 http://zookeys.pensoft.net Copyright Marina Vilenica et al.. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. RESEARCH ARTICLE Launched to accelerate biodiversity research A peer-reviewed open-access journal