September nest phenology report

Many bumble bee species have already completed their life cycles and their nests have senesced - meaning they have completed their reproductive output and declined. Other species, like the common eastern bumble bee, hang on later into the season and have just begun producing males and new queens. 

Colonies produce queens when they are able to bring in enough pollen. Queens and workers both develop from fertilized eggs. The only difference is how much they are fed as larvae. Once new queen production starts, the old queens will usually switch to laying unfertilized eggs, which develop into males. These males and new queens will leave the nest to mate with males and queens from other nests. Males and new queens are known as reproductives, and once they are produced, the worker population within a bumble bee nest will start to dwindle, and eventually the nest will die.