characterized by an internal chamber, pitfall traps are thought to have evolved independently at least six times. this particular adaptation is found within the families sarraceniaceae "(darlingtonia, heliamphora, sarracenia"), nepenthaceae ("nepenthes"), cephalotaceae ("cephalotus"), and eriocaulaceae ("paepalanthus)." within the family bromeliaceae"," pitcher morphology and carnivory evolved twice "(brocchinia" and "catopsis)." because these families do not share a common ancestor who also had pitfall trap morphology, carnivorous pitchers are an example of convergent evolution.