Apart from an appetite for munching insects, there is one other thing that carnivorous plants have in common.  They all live in inhospitable places in nutrient poor soils.  Not surprisingly the two things are connected.  The plants use insects to supplement their diet, supplying them with minerals and nitrogen, which is essential for plant growth, and is in limited supply in the poor soils in which they live. They all lure, capture and kill unwary insects but have evolved many different ingenious and cunning ways to nail them.

 

Carnivorous plants are found all over the world from the rainforests of Borneo and South America to the bogs and moors of Britain. Far from being similar, they have more fiendishly different kinds of traps than a Harrison Ford movie.  Traps fall into two main types, active and passive.  Passive traps don’t move, but that certainly doesn’t mean that they are boring. They are very cleverly designed to entice insects in.

 

Pitcher plants like Sarracenia are passive, pitfall trappers, but they don’t just rely on an insect stumbling in by accident.  The victim is lured with sweet nectar baits often laid in a trail that the insect follows, past downward pointing hairs to another bribe, the point of no return.  The unsuspecting hungry prey walks on to a waxy surface, far more slippery than ice, then slips and slides down a steep slope into the bottom of the waiting trumpet of the plant.  German and French researchers have been working out just how insects which can walk on glass, lose their footing on the wax of the plant and fall to their doom.  ‘We looked at the microscopic surface of the wax, and it turns out to have two layers.  The top one clogs up the soles of the insect’s normally super adhesive feet. The lower one has a surface like a spiky sponge, reducing the contact area between the surface and the foot.  The insect does not have a chance,’ explains Laurence Gaume, a botanist at the University of Montpelier.

 

Having landed in a pool of liquid at the bottom of the pitcher, the body is digested by enzymes secreted by the plant, or bacteria in the fluid.  Some pitcher plants even have insects that lay their eggs on them.  The hatched maggots get to work feeding on the corpses in the pool and give the plant a helping hand with digestion. The plant absorbs the nitrogen rich insect poo like a fertiliser.  Living in high rainfall areas these plants have to make sure that their pitchers do not fill up with rain and flush out their hard won insects, so most have overflows like the one in a bath, or lid–like umbrellas to protect the opening. The largest pitcher plant in the world has 3 foot high trumpets, and can devour whole armies of flies and wasps.