Attenborough narrates the astonishing bloodletting/beeheading in the bit after the link. Click through and watch; its visceral..

The male bees are adapted to pursue one of two tactics for securing a mate.

Smaller, minor males patrol either flower patches where females forage, or around the periphery of the entrances to females’ burrows.

However, much larger major males patrol the entrance sites for emerging females, seeking to mate with them as soon as they appear.

Up to 90% of all females are mated by major males immediately upon their emergence.