Yellow jackets (wasps) are marked with bright yellow and black pattern. They appear to be hairless and are about 3/8 to 5/8 inch long. The bald-faced hornet is similar in appearance except that it is black and white and 5/8 to 3/4 inch long. The males and queens are produced in the colony in late summer. They mate, and the fertilized queen overwinters in a protected site. In the spring she seeks an appropriate nesting site in which she builds a paper nest using chewed up wood fibers. Eggs are laid within the cells of the nest, and the young larvae are fed bits of chewed meat or insect parts by the queen and later by the workers. Yellow jackets and hornets build their flat paper nests in stacks which are surrounded by a paper envelope. Bald-faced hornets prefer to build their nests in trees and on the sides of buildings. Unlike bees, these wasps aggressively defend their nests and can inflict multiple stings. They produce very large colonies, some containing as many as 30,000 individuals. These insects are considered to be beneficial because a nuisance, however when they build nests in or near structures scavenge for food in recreational areas and in other places frequented by humans, and seek overwintering sites within structures.