Yellow jackets are bee-sized social wasps that build paper nests, usually underground. They usually have beelike black and yellow bands on their abdomens, but they are not hairy, nor do they collect pollen, like honeybees. Yellow jackets have yellow or white faces. When resting, they usually hold their wings down their back (not spread out). Right before landing, they often fly quickly side to side.
Yellow jacket nests are made of paper like that of paper wasps, but they have multiple parallel layers of comb with downward-facing cells (paper wasps always only have a single layer of cells). Yellow jacket nests are always enclosed in a wood-pulp paper envelope built by the wasps.
Yellow jackets are widely, and incorrectly, called "sweat bees" in Missouri.
Yellow jackets are a significant stinging threat: They nest in colonies and aggressively defend their nest as a group. Individuals can sting repeatedly.