This a large hornets nest I noticed today. It is very exposed to the elements.
Hornets appear very similar to common wasps, but are larger and coloured chestnut-brown rather than black and yellow. They build papery nests in hollow trees by chewing the wood and mix it with saliva to form a lightweight, waterproof and robust material similar to paper mache.
The life cycle is similar to that of the common wasp. Newly-mated queens hibernate during the winter, and emerge in spring to begin building a nest. They lay eggs that hatch into sterile female workers who take over nest building and collecting food for the developing larvae. Later in the summer males and fertile females hatch. These mate and the females become next year’s queens. The males, old queen and workers die in the autumn.
They are much less aggressive than wasps, and also hunt at dusk, unlike wasps.