Until the middle of the 20th Century, scientists believed that queen bees took only one mating flight in their lifetime. It wasn’t until the 1940’s that a scientist who was studying queen bee mating behavior discovered that queen bees take multiple mating flights. The scientist (Roberts, 1944) determined that the number of mating flights ranged from one to five. It took another ten years or so for another scientist (Woke, 1955) to postulate and prove that queen bees not only take multiple mating flights, but also mate with multiple drones during this flights.
We now know that queen bees mate with approximately 10 to 20 drones, typically over the course of several flights. Why so many flights and drones? By spreading the mating process both over time and over multiple drones, the queen limits the probability that she will mate with a drone that shares the same sex alleles. This varied mating program minimizes the chances of inbreeding and maximizes the chances for “hybrid vigor.”