The Carnivorous Plant FAQ v. 12

Q: Exactly how do these plants capture prey? Answer #2--sticky traps

A: Many plants have sticky leaves. The source for the stickiness can be gumminess on the surfaces of the leaves, or mucus produced on stalked glands. Usually the plants have evolved this stickiness to protect them from invaders. For example, the next time you see tomato plants in a garden, look closely and you will probably find dead bugs attached here and there to the leaves. It does not take much of a modification to transform this self defense system to an offensive, carnivorous system. The evolutionary pathway leading to sticky traps is easy to envision.

Examples of carnivorous plants with a primitive sticky traps are in the genus Byblis. These plants have stalked glands that produce a gummy mucus. Bugs caught on the leaves are not digested by plant enzymes. Instead, digestion is completed by symbiotic bugs. The resinous Roridula plants operate much the same way. The majority of sticky trap plants produce digestive enzymes.

Sometimes, the plants exhibit leaf motions that bring digestive organs into contact with the prey--for example, the slime-bearing tentacles of many Drosera bend towards the captured prey. Sometimes, even the entire leaf bends over the prey, clasping it in an enzymatic embrace. Pinguicula leaves often roll up near the margins. These motions do not help capture the prey--instead, they merely help speed digestion, presumably to improve the digestive efficiency but also probably to help foil marauding kleptoparasites.

A few plants, such as D. glanduligera, D. burmannii, and D. sessilifolia have much faster moving glands--especially on the leaf margins--and these glands can carry or even catapult prey into the center of the leaf, where a forest of glandular hairs await.

A few sticky plants have brightly colored glands or boldly contrasting plant parts (such as D. solaris). It may be that such coloration might help attract prey. Other plants have odors---Drosophyllum lusitanicum has a honeylike scent, while some Pinguicula and Byblis have a fungal odor.

Page citations: Lloyd, F.E. 1942; Rice, B.A. 2006a.

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Revised: 2018
©Barry Rice, 2018