I am not surprised to learn…Yellow Jackets are at their population peak in the late summer and early fall. This is when nests can have populations of 2,000 to 4,000 worker yellow jackets (all female), some drone (male) yellow jackets and up to 50 queens at once. The workers will soon start dying off until late in autumn when until the nest population is reduced to a small number of queens that will survive the winter.
Until this time of year, Yellow Jackets are less scary as they go about the business of pollen collection and preying on garden pest insects and spiders. It’s when they switch from a search for protein sources for feeding larva to sugar sources for the queens in the nest, who must fatten up to survive their winter dormancy… that we encounter most aggressive encounters with this species of hornet. I predict most folks who enjoy the outdoors have a frightful Yellow Jacket tale to tell.
(Fact finding help- Discovery Place- Nature)