Some male butterflies go to extreme lengths to ensure their paternity – sealing their mate’s genitalia with a waxy “chastity belt” to prevent future liaisons. But female butterflies can fight back by evolving larger or more complex organs that are tougher to plug. Males, in turn, counterattack by fastening on even more fantastic structures with winglike projections, slippery scales or pointy hooks.
It’s a battle that pits male and female reproductive interests against one another, with the losing sex evolving adaptations to thwart the winner’s strategies.
Could this sexual one-upmanship ultimately result in new species? It’s a longstanding hypothesis and one that would help explain how butterflies became so diverse. But it has proven difficult to test. MORE
Header image: The size and shape of mating plugs often varies by species. This female Acraea omrora features a small plug with sharp hooks, attached to her abdomen by her partner to ward off rival males. Credit: Jeff Gage/Florida Museum.