Most of my publications deal with dragonflies and this groups is still at the center of my attention. I worked extensively on Europe (e.g. the EU Red list, Atlas of the European Dragonflies and Damselflies), southwest Asia (mainly Turkey), New Guinea (amongst others fieldguides for dragonflies and damselflies) and at present the Indian Peninsula (mainly the Himalayan region). Besides taxonomy and phylogeny I have a strong interest in biogeography and conservation.
Much of my work on dragonflies is in close cooperation with KD Dijkstra, Rory Dow, Albert Orr, Stephen Richards, Gunther Theischinger and Jan van Tol. My current work focusses on the Himalayan region for which I hope to produce a field guide, unravelling the biogeographical history and establish dragonflies as tool for the conservation of freshwater ecosystems. Many of the projects I work on make use of molecular techniques and the extensive DNA-library of odonates housed at Naturalis and for this work I cooperate with Frank Stokvis from the molecular lab or Naturalis.