My first Sarracenia flower, on a purple pitcher plant, has finally opened enough for me to see the cool trick I've heard about. Photos I've run across didn't show enough for my curiosity to be satisfied. To prevent self-pollination, insects must pass over a modified stigma before it reaches the pollen from the flower itself, pollinating the flower from an outside source, before it reaches the flower's pollen. Then it escapes under the petals, not passing the stigma again.