Biological collections may often be an important source of information about natural history, behavioral habits, and ecology as they contain samples of organisms collected in different places and moments in times. In here, we used museum specimens to examine how populations of three species of Bombus-Bombus bellicosus Smith, Bombus morio (Swederus), and Bombus pauloensis Friese-vary over time with respect to abundance and biomass of each sex and caste. The study included all specimens of these three bumblebee species deposited in the insect collection of the Federal University of Parana that were collected in eastern Paraná, in southern Brazil. Seasonality is most noticeable in the peak of queen activity (number of individuals in collections) in early spring, after dormancy during the winter. Queens then founded nests, and workers and males began to become more abundant during spring and summer. Worker abundance peaked at the end of summer and beginning of fall and may correspond to increasing activity for production of new males and gynes. Male abundance peaks are during the reproductive period. Thus, we show with these data and analyses that museum collections can be very useful tools to examine temporal and ecological processes. We recommend greater use of museum accessions to explore these kinds of patterns that may otherwise go unnoticed.