Accepted Article This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1111/plb.12475 This article is protected by copyright. All rights reserved. Received Date : 14-Mar-2016 Revised Date : 13-May-2016 Accepted Date : 30-May-2016 Article type : Research Paper Editor : J Arroyo Contribution of gall microscopic structure to taxonomy of gallicolous aphids on Pistacia R. Álvarez 1 *, J-J. I. Martinez 2, 3 , A. L. Muñoz-Viveros 4 , P. Molist 5 , J. Abad-González 6 , J. M. Nieto Nafría 7 1 Departamento de Biología Molecular-Área de Biología Celular, Universidad de León, León, Spain. 2 Department of Animal Sciences, Faculty of Sciences and Technology, Tel Hai College, Tel Hai, Israel. 3 Lab. of Animal Ecology & Biodiversity, MIGAL - Galilee Research Center, South Industry Zone, P.O.Box 831 Kiryat Shmona, 11016 Israel. 4 Laboratorio de Control de Plagas, Facultad de Estudios, Superiores Iztacala, Universidad Nacional Autónoma de México, Tlalnepantla, Mexico. 5 Department of Functional Biology and Health Sciences, University of Vigo, Vigo, Spain. 6 Departamento de Economía y Estadística, Universidad de León, León, Spain. 7 Departamento de Biodiversidad y Gestión Ambiental, Universidad de León, León, Spain. *Corresponding author. e-mail: ralvn@unileon.es ABSTRACT Aphids inducing galls on Pistacia plants belong to the tribe Fordini. According to the classification of Heie & Wegierek (2009), the genera are grouped into three subtribes. Previous microscopic studies showed that this taxonomy is not consistent with the histological characteristics of the galls. In this paper, galls induced by Aploneura lentisci, Asiphonella cynodonti, Forda riccobonii, Slavum wertheimae and Smynthurodes betae were analyzed for the first time, together with nine other galls previously described, and new groupings were determined based on histological features. The main results indicated three groups of galls: the first group comprised closed galls, induced by Baizongia pistaciae, Geoica utricularia, Rectinasus buxtoni and Slavum wertheimae, the second group included two species of Geopemphigus (G. blackmani and G. torsus), and the third group was divided into two subgroups, the first comprised