The nest is made from chewed wood fibres mixed with saliva. It has open cells and a cylindrical column known as a “petiole” attaching the nest to the substrate. The wasps produce a chemical which repels ants and secrete it around the base of the petiole to avoid ant predation.

A solitary female queen starts the nest, building 20–30 cells before initial egg-laying. This phase begins in spring, depending on climatic conditions. She fashions a petiole and produces a single cell at the end of it. Six further cells are then added around this to produce the characteristic hexagonal shape of the nest cells. One egg is laid in each cell, and as it hatches, each larva holds itself in the vertical cell by pressing its body against the sides.

The queen now divides her time between feeding the larvae on the juices of masticated insects and nest building. Once the larva reaches full size, it spins a cover over the cell, pupates and metamorphoses into an adult. When enough adult workers have emerged, they take up most of the colony’s foraging, brood care and nest maintenance throughout their 10 week life cycle.

The queen, who is now fed by the workers, concentrates all her energy on reproduction. The spherical nest is built from the top downwards with successive combs of cells separated by petioles. The queen larvae, known as “gynes”, are reared in larger cells in the lower combs. The finished nest may contain 5,000–10,000 individuals.

Each wasp colony includes one queen and a number of sterile workers. Colonies usually last only one year, with all but the queen dying at the onset of winter. New queens and males (drones) are produced towards the end of the summer, and after mating, the young queen overwinters in a hole or other sheltered location, sometimes in buildings. Wasp nests are not reused from one year to the next.