Bald-faced hornets live in aerial nests and are very social insects. The adult hornets are works including sterile females, queens, and males, which come from unfertilized eggs and appear in the late summer. The only females that overwinter are those that have been inseminated, and they live in sheltered places through the winter.
In spring, the females use chewed cellulose material to create a paper nest of dozens of cells in a paper envelope. Each egg is laid in a cell as the cell is constructed. The queen then feeds the larvae with nectar and arthropod proteins. The first five to seven workers emerge after about 30 days and take over all work other than laying eggs. Eventually, the nest will contain three to five, rounded paper combs which are opened ventrally and attached one below the other, covered with a many-layered envelope.
Nest sizes can reach up to 3,500 cells in five combs; however, they tend to consist of less than 2,000 cells in three to four combs. Reproductive cells are made in which males and queens will be reared, and males are usually reared in the old worker cells. At this point, the colony is entering a decline. The new males and queens will then leave the nest and mate. The inseminated queens will hibernate to survive the winter, while the founding queen, the works, and the males die.