
Unlike with most species of bees (there are 20,000+ species in the world), the male of the European carder bee (Anthidium manicatum) is significantly larger than the female.
This is a result of their peculiar behaviour where the males chase away anything that isn't a female of his species from "his" plants. And since when chasing away, size is an advantage, evolution has led to larger males.
But that's not all it has equipped the males with. Since stingers in bees and wasps are modified ovipositors, ie lady parts, no male has a stinger. But some sort of weaponry could be helpful when chasing away other bugs so the males of this species actually have five black spikes on their tail which they use as weapons when defending their turf. They don't really show in this shot, but in part 1, three of them are clearly visible: www.flickr.com/photos/tinyturtle/53906531828/
Also, today I stumbled on a *really* great video on YouTube about this bee which shows a lot of this in wonderful detail. It's just two-and-a-half minutes long, but I really recommend you to check it out here: www.youtube.com/watch?v=qX6d7fDbJp8