Very few studies on population sizes of invertebrates have been conducted in the past, and even fewer were based on standardized methods documenting sampling locations exactly. Knowledge on long-term trends in insect communities is thus very limited. Here, we repeated a semi-quantitative study on grasshoppers, true bugs, planthoppers and leafhoppers conducted in the Weser floodplain grasslands (northwestern Germany) in 1951. It was supplemented by a study on grasshoppers, planthoppers and leafhoppers which were caught with standardized methodology in the early 1960s on dry grasslands of eastern Germany and repeated in 2008/2009/2010. Trends over time gave a mixed picture. In the Weser floodplain, species numbers of grasshoppers remained stable; those of planthoppers/leafhoppers and bugs showed a clear increase. Bugs also increased in individual numbers, whereas the abundance of the other two groups declined strongly by more than 60%. Similar trends were found for the dry grasslands: Richness of grasshoppers and planthoppers/leafhoppers remained constant over time. Individual numbers were only available for the latter groups; they declined by 50-70 % in all three paired study years we had data for. Our data do not support the idea of dramatically decreasing species numbers of insects in grasslands but do raise concern with respect to dramatic losses in population sizes that should receive more attention in conservation biology.