In butterfly battle of sexes, males deploy 'chastity belts' but females fight back

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.