The study of plant galls and the keys to their identification have an almost century-long tradition in the Netherlands, culminating in several revised editions of Docters van Leeuwen’s “Gallenboek” by the first author. For Belgium and Luxembourg, Jacques Lambinon substantially contributed with his “Aide-mémoire de cécidologie”, which was later revised and enhanced by the second author.

The recent publication by the first author of “Plant Galls of Europe” also made a new advance in plant gall identification. This is a thorough revision of Buhr’s comprehensive keys with additions from Houard and of many new records and descriptions gathered from the literature.

Plant gall records have also significantly increased through biological data schemes that improve knowledge about the occurrence and abundance of species. Among many other websites, Dr Willem Ellis’ “bladmineerders.nl” allows contributors from all over Europe, and especially from the Benelux, to benefit from an acute validation of their discoveries.

Reflecting the interest that cecidology recently gained among naturalists, we now propose these new keys, based on updated records, knowledge of species’ biology and taxonomy. These are the first covering the identification of galls on plants, mosses and fungi for Belgium, the Netherlands and Luxembourg. This resulted in more than 1500 gallmakers about twice the number of species covered in the 2009 edition of Docters van Leeuwen/Roskams Gallenboek for The Netherlands only.