How A Sundew Eats!

Drosera capensis ‘Cape sundew'

     This Drosera capensis aka Cape Sundew, is a carnivorous plant that has a fascinating process of capturing and digesting insects.  The flat leaves on this sundew are covered in small stalked glands or tentacles.  The tentacles are hair-like filaments, and at the end of is a small gland that produces a tiny drop of dew: a clear, gluey mucilage that is extremely sticky.

The Tentacles on Drosera capensis ‘Cape sundew'

The Tentacles on Drosera capensis aka Cape Sundew

A small flying insect may catch sight of the glistening droplets and mistake them for a flower's sweet nectar. It alights on the leaf and is immediately caught in the glue, and struggles to free itself.  The more it thrashes, the more mired it becomes in the tentacles.  The tentacles quickly begin to move, carrying the victim toward the center of the leaf, where more glands await.

A small insect caught in the tentacles of Cape Sundew

A small insect caught in the tentacles of Cape Sundew

     Usually the prey of sundews suffocate when the breathing holes (spiracle) along their abdomens are covered in glue.  Once an insect is caught, the highly developed glands begin to secrete a complex juice of enzymes and acids that rapidly covers the insect's body.  In a matter of hours or days, the digestive juices liquefy the softer parts of the insect. The glands then begin to reabsorb this nutritious soup.  On larger insects the leaf will curl around its prey.

The leaf is bending around a spider. Notice how the end of the tentacles have moved to trap and digest the spider.

A leaf has folded to trap and digest a large insect.  Notice the leaf on the left with many small bugs that have been trapped.  The leaf doesn't fold on small insects.

     

After digestion, the tentacles usually dry up and return to their normal upright position. The shriveled carcass falls from the leaf, is washed off by rain, or simply remains as a dire warning to future prey. Dew drops reappear, and the leaf is ready for another meal. Sometimes older leaves remain curled up even as the leaf turns brown and dies. During their active growth cycle, most sundews continually replace older leaves with new ones.

Drosera capensis ‘Cape sundew'