There are around 800 species of thick-headed flies or conopids, and they’re all parasites. They use the hard tips of their abdomens like can-openers to prise apart the body segments of bees and wasps, so they can lay an egg inside. They even do this while flying. A conopid can chase down a bee, grab it in mid-air, open it up, and implant it with an egg, without ever touching the ground.