All castes and species of bee have four wings. The pair of wings that is closer to the head is always larger and folds over the rear pair when the bee is at rest. The rear pair is shorter and hooks into the forward pair when unfolded for flight.
The rear pair has a line of hooks on the front edge that connects into a line of grooves on the back edge of the other wings. This couples the wings together and makes them into a single, large flight surface. Some bees have very short rear wings and cannot fly. The wings beat very rapidly in short, choppy strokes that cause the wing surfaces to flop backward and reverse direction. This allows bees to fly despite their aerodynamics being very different from fixed-wing fliers like airplanes.