The Auchenorrhyncha, the planthoppers, cicadas, froghoppers, spittlebugs, treehoppers and leafhoppers, arc often largely unknown even to amateur naturalists and biologists. The main reason apart from their small sizeis certainly the apparent or perceived difficulty of identification. Due to their high abundance, which can exceed 5000 individuals and several grams of biomass per square meter, they are among the dominant herbivore groups and must be considered as a significant component of terrestrial animal communities. On the one hand, they consume plant assimilates and biomass; while on the other hand, they are an important food source for predators and parasitoids. Due to their high degree of host specialisation and their ability to transmit plant diseases, they may alter the competitive relationships among plant species, which may in turn affect the composition of the plant community. The energy flow from the use of the honeydew produced from the feeding of leaflwppers and planthoppers has been little investigated. As pests of cultivated plants they have gained economic importance, particularly as vectors of plant viruses and phytoplasmas as well as by direct sucking on vessels and tissues. More recently, Auchenorrhyncha have been used as a basis for conservation planning, because they are particularly suitable for the evaluation of habitats, management programs and successional stages.In order to facilitate the study of Auchcnorrhyncha within ecological and conservation projects and to stimulate further research on their taxonomy, ecology and zoogeography, we decided to create a modern key to the central European fauna. The compilation would not have been possible in such a short time without the generosity of the publisher, who allowed us to include the excellent figures of Frej Ossiannilsson's work "The Auchcnorrhyncha of Fennoscandia and Denmark". Thus we were forced to achieve his high standard of illustration. During the process of writing we were continuously facing taxonomic and nomenclatural problems. We could solve some of them, hut a solution of several others was clearly beyond the scope of this book (e. g. in the genera Cix•ius, Tettigometm). In these cases we tried to outline and characterise the situation in order to stimulate further research. Originally we had planned this book only to treat central Europe, but later we decided to include also northern Europe and the British Isles, which did not mean too much additional effort due to Ossiannilsson's work. So the northern limits of the coverage became clearly defined, whereas the delimitation in the south and cast is more difficult due to the lack of natural borders. Thus, further species, which are not yet treated here are likely to be found during future field work. After initial reluctance, we also decided to produce distribution maps, even at the risk of drawing an incomplete or even misleading picture in some cases. The final argument was again, however, that the presentation of the status quo should be the best stimulation for future stud...
