Yellow jackets and hornets differ in where they build their nests and how they eat. Yellow jackets build nests in soil, while hornets build their nests in trees. Yellow jackets are scavengers, eating dead insects and sugars. Hornets only eat live insects.
Yellow jackets and hornets both belong to the Vespid family of wasps. They are social wasps that tend to defend their territory. Many are encountered by humans since they build their nests in areas where humans tend to congregate.
Both the yellow jacket and hornet construct nests out of wood fiber. The queen gathers wood fibers in the spring, turning them into a papery pulp. She uses this pulp to build an open, umbrella-shaped nest. If she is a hornet, she constructs her nest hanging from a tree branch or other aerial perch. A yellow jacket queen prefers construction below ground. These underground nests are often encountered when mowing.
Yellow jacket and hornet nests degrade over the winter and are rebuilt each spring in warmer temperatures. The queen hides during the cold winter, emerging in the spring to build a new nest and lay her eggs. This queen is replaced by a new queen in late summer or fall. The new queen mates and retires until the next spring to continue the cycle.