In late summer, the fully grown larvae leave the water. The larvae form into pupae in these cells. In less than two weeks, adult water scavenger beetles come out of the cells. The adults crawl back to the pond from where they developed as larvae. There are one or two generations of giant water scavenger beetles each year.
Some adults live through the winter hidden under plant litter.
Other adult water scavenger beetles live under the ice and are active all winter long. They survive by taking air from air pockets found under the ice. These air pockets are between the water and ice. The beetles are eaten by fish, other larger insects in or near the pond, and birds. Voles and raccoons eat them in the pupa stage.