Insectivorous or carnivorous or plants have a trapping device for catching small living animals. They decompose the proteins of insect bodies, with the help of acidic enzymes and then use special glands to absorb decomposed animal products.
Over the aeons, such plants have adapted to growing in areas low in nitrogen, by developing devices to catch insects. Protein is then extracted in the form of nitrogen from the insects body. These plants originate in swamps and boggy wet places, often not in ‘real’ soil. The devices include sticky traps, others that work on the ‘pitfall’ or ‘slippery slide’ method, and the one most people know, the complicated ‘rabbit trap’ which shuts quickly when stimulated.
The simplest trap is found in the sundew or Drosera spp. Sundew leaves have been modified into hair-covered tentacles that catch, hold and digest insects. At the tips of these tentacles is a honey-like blob that attracts insects, usually small ones such as mosquitoes or ants. The insects stick to the droplets, then other tentacles are stimulated to fold over the entire insect, suffocating it. The sundew then secretes a fluid to break the body down and absorbs the protein. Sometimes you may see the empty cases of insect bodies left on the sticky leaves.
The Venus flytrap
The carnivorous plant that many people know is the ‘Venus flytrap’. It certainly looks like a trap, with leaves like an open shell. The inside of the shell is reddish and attracts insects. On this inner surface are three bristly hairs, sometimes more. When an insect touches these hairs, it stimulates the leaves to immediately snap shut. The two sides of the leaf can stop even a large blowfly from escaping. The plant digests the insect’s body fluids, then opens after several days to await more prey. Usually one leaf of the Venus flytrap opens and shuts three or four times, then its catching mechanism loses energy and that leaf dies. But, there are smaller leaves growing all the time. They will live quite happily on a window-sill, if given plenty of water in summer, and then allowed to dry out in winter.
Pitcher plants are carnivorous plants with another bizarre way of trapping. Their name is evocative of the shape of their leaves, which grow in a tubular jug or pitcher shape, often with an umbrella cover. The open end of the tube has nectar glands, and lots of honey to attract insects. Once an insect travels down the tube, it skids on the walls to the bottom of the tube. Here, the insect drowns in the plant juices and acids, and is absorbed as food. Famous naturalist Charles Darwin called them the most interesting plants in the world.
Cultivation of carnivorous plants
- Many carnivorous plants can be grown in pots or in terrariums indoors, or outdoors if you have a boggy spot to which you add peat moss, coarse sand or sphagnum.
- Keep pots in a well-lit situation in-doors-leaves will go lanky if light is too dim.
- During summer they should not be allowed to dry out, so keep them well-watered, even leave them standing in a saucer with constant water.
- During winter they may die back. The Venus flytrap, in particular, will lose its leaves. You may think the plant has died but this is its dormant time. It will come back to life in spring, so this is the time to repot it, using a mixture of peat moss and coarse river sand.
- There is really no need to feed your carnivorous plants as they will catch plenty of their own prey.