HOW DOES A PITCHER PLANT ATTRACT, CATCH AND TRAP INSECTS

Pitcher plants are carnivorous plants whose prey-trapping mechanism features a deep, bulbous cavity filled with a digestive fluid. The traps of what we consider to be ‘true’ pitcher plants are created from modified leaves, however they are not simply folded into a tube - the process is far more complicated!

The process begins when the tip of the leaf begins to extend into a tendril. This gains support for itself by twisting around the stem of another plant, usually making no more than a single turn. The tip then begins to swell, drooping under its own weight. Then, quite suddenly, the swollen tip begins to inflate with air.

How does a pitcher plant catch and trap insects?

As the tip balloons larger and larger, flecks of colour start to appear in the walls of the growing cavity making it recognisable as the trap it will become. At this point the cavity begins to fill with fluid, and once it has fully matured a lid-like segment at the top of the trap opens and the plant is ready to receive its ‘visitors’.

Pitcher plants entice insects to their traps using a fragrant nectar. Any insects that encroach the trap are at risk from a ribbed, widely protruding rim known as the peristome. This is coated with a waxy film which when dry is not much of a threat, but after a period of rainfall the rim becomes covered with a film of water which confounds the surest of insect feet. Inevitably any insect stepping onto the peristome will slip down past the inner walls of the pitcher but these too are coated by a flaky waxy surface that peels off and clogs the feet of insects so that they lose all chance of adhesion.

As the victims tumble into the water and struggle to save themselves, the disturbance stimulates glands in the walls of the pitcher and these start to discharge a digestive acid. This is so powerful that a fly can be reduced to a hollow shell within days and a midge will entirely disappear within hours. The whole device is so effective that these pitchers can trap not just small insects, but larger prey such as cockroaches, centipedes and scorpions. In fact, some of the larger varieties of pitcher plant such as Nepenthes rajah, Nepenthes rafflesiana and Nepenthes attenboroughii are even able to catch prey as large a rat.

For related articles click onto the following links:
HOW TO GROW PITCHER PLANTS
HOW TO GROW THE PITCHER PLANT FROM SEED
WHY DO CARNIVOROUS PLANTS EAT ANIMALS AND INSECTS
PITCHER PLANT