 U. dichotoma |
 Utricularia bladders |
A plant is carnivorous if it attracts, captures, and kills animal life forms. It must also digest and absorb the nutrients from the prey to qualify as a carnivorous plant.
There are many noncarnivorous plants that do some (but not all) of these things. For example, flowers attract pollinators (such as insects, birds, and other creatures, even humans!); some plants (such as orchids, jack-in-the-pulpits, and waterlilies) temporarily trap insect pollinators to ensure pollen transfer; plants such as members of the American genera Ibicella and Proboscidea trap and kill insects by their sticky leaves (but do not digest the prey). All plants absorb nutrients either through their roots or leaves. However, even though these plants do some of the things that carnivorous plants do, they do not fulfill all of the criteria necessary to qualify as a carnivorous plant. Only plants which attract, capture, kill, digest, and absorb prey are truly carnivorous.
In recent years people have been realizing that nature is not quite so black and white as we would like. Some plants are not quite carnivorous, but are not quite noncarnivorous, either! For example, there are sticky plants which harbor bugs on them. These bugs crawl freely on the plant and eat the insects trapped by the sticky leaves. The bugs excrete (i.e. poop) on the leaves, and the plant absorb nutrients from the poop. Other plants rely on bacterial decomposition to break down the captured prey. Are these intermediate cases carnivorous? Or should they be called semi-carnivorous or sub-carnivorous? Scientists and philosophers are still pondering these questions.
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