The two families are distinguished by their flowers, Nepenthaceae having separate male and female flowers while Sarraceniaceae are hermaphrodites; and by the leaf structure, Nepenthaceae having tendrils.
While Nepenthaceae and Sarraceniaceae are the best-known and most speciose groups of pitcher plants, two more obscure pitcher plant families exist:
- Cephalotaceae is a monotypic family with but one genus and species, Cephalotus follicularis. This species has a highly-developed but very small pitcher (a few cm at most) and is restricted to the southeast corner of Australia.
Here is a picture of a Cephalotus trap
- A few species of bromeliads Bromeliaceae, such as Brocchinia reducta and Catopsis berteroniana are known or suspected to be carnivorous. Bromeliads are monocots, and given that they all naturally collect water where their leaves meet each other, and many species are epiphytic and collect detritus (the tank bromeliads), it is not surprising that a few should have developed the habit a bit further into carnivory by adding wax and downward-pointing hairs.
Like most carnivorous plants Cephalotus and the carnivorous bromeliads are found in regions with poor soil (or other nutrient-poor conditions, such as that experienced by epiphytic bromeliads), bright sunlight, plentiful moisture, and regular ground fires or other disturbance.