Citizen science – the involvement of the public in scientific research – has become an emerging field, both as a research approach and as a discipline (the science of citizen science) by itself. The ‘Mückenatlas’ (German for ‘mosquito atlas’) was launched in 2012, shortly before citizen science also gained momentum in Germany. The goal of the ‘Mückenatlas’ is to support mapping the occurrence and distribution of native and introduced mosquito species. Therefore, people collect and submit physical mosquito samples to the responsible research institutions. In return, participants receive an individual answer with information about the biology of the captured spe¬cies and, if desired, a personal marker on the collectors’ map on the ‘Mückenatlas’ website. In this thesis, the project was evaluated from three perspectives, based on current controversies in citizen science: as a monitoring method, as a data source, and as a public outreach activity. The general aim of the dissertation was to assess the contributions of the opportunistic data collection of the ‘Mückenatlas’ project to mosquito research in Germany. The ‘Mückenatlas’ performance as monitoring method was evaluated by comparing it to a professional monitoring approach. The results showed that monitoring by professionals allows for a better coverage of land use types and species richness, whereas the citizen science approach provides important data from urban areas and can very well detect invasive species. By investigating the ‘Mückenatlas’ data collection as data source for research, anthropogenic and environmental factors were identified as drivers of the spatio-temporal variation in the numbers of submissions. Despite this bias, a study of the effects of urbanisation on indoor mosquito communities showed that opportunistic data have the capacity to confirm findings and generate novelty. Finally, considering the ‘Mückenatlas’ as an outreach activity demonstrated the positive association of mass media reports with the number of submissions across time and space. In addition, the style of the titles and texts of media reports, as well as an already raised media and public attention towards mosquito topics, increased the responsiveness of participants. The findings of this thesis show that the opportunistic data collection of the ‘Mückenatlas’ can make a crucial contribution to mosquito research, especially in gaining insights into species occurrence through the sheer number of samples submitted. Recommendations are made on when and how citizens can be involved in formal mosquito monitoring programmes, what biases and patterns to consider in data analysis, and how communication strategies can influence participation and affect the data.
