Distribution of species richness of Hydradephaga in Switzerland. A. Map with the total number of species recorded per 5×5 km grid, all data and all years combined. The lowland areas of Switzerland are generally those with the highest diversity of Hydradephaga, but some rich areas are also found on higher elevations; B. Altitudinal distribution of species richness. All altitudinal information (where provided) for each species was considered and aggregated by 200 m altitudinal class.