Around 50 different species of gnats (mosquitoes) have been detected in Austria to date. These are not only annoying, they can also be vectors (= carriers) of human pathogens such as the West Nile virus. Exotic mosquito species in particular (e.g. the tiger mosquito Aedes albopictus), which have only colonised Europe in recent decades, are often potential vectors of a variety of pathogens, such as the dengue virus or chikungunya virus. Many of these exotic pathogens cannot be transmitted by the native mosquito species. As the various species of mosquito differ in their capacity to transmit diseases, it is essential to determine which species occur in Austria and how high their infestation with human pathogens is.