Just like many other insects there are many different kind of species of bee and they're reproductive processes vary wildly across both biology and practices. So to truly answer the question 'How Do Bees Mate?' we must first look at the differences across species:
Honeybee colonies reproduce when a mature queen leaves the nest to find male drone bees from other hives. Male drones mate with the queen using their endophallus, this process will occur up to 20 times until the queens oviducts are full of semen and any excess is stored in the spermathecal for later.
A female queen will leave the nest in search of male drones from other hives to mate with. Once the process is complete she will return to the hive and begin to produce young.
Male bumblebees will forcefully knock a female queen bumblebee from mid flight to the ground to mount her thorax and mate with her.
Carpenter bee reproduction starts when a group of male and female carpenter bees begin a 'bobbing' dance. This will normally contain approximately 12 males and 4 females. Once the dance is complete the females will take to the air with the males following closely behind. The males will attempt to mate with the females with the final goal being to position their abdomen directly above that of the females by climbing on to her back mid flight.
Male bees will wait in large numbers at the entrance to the females nest. When the female burrowing bee emerges the males will fight to the death for the opportunity to mate with the female. Male burrowing bees outnumber female bees 100/1 so the battle that ensues can lead to huge losses. The video below show the fascinating but deadly mating ritual...