How does a Cobra lily trap its prey?

March 4th, 2011 | by lucy |

In a sun-lit meadow on the mountainside, a large grove of curving plants grow close together in the marshy grass, which glistens with cool running spring water.  Humans are struck by the resemblance of these pitcher plants to hooded cobras, poised to strike, and have christened them Cobra Lilies, but for an insect there is nothing threatening about them at all.

On the contrary, they are very enticing.  The pitcher plant surface is covered in scattered nectar glands where insects can feed, and there are even more on a bright red appendage, forked like a snake’s tongue. The tongue hangs down from a mouth-like opening, and just inside there is a particularly copious supply of the tempting sweet stuff.

For us, the snake illusion is completed by the pattern on the domed leaves, giving the impression of scales.  They are translucent aeroles that flood the pitcher with bright light. An insect might be reluctant to enter a dark interior, but is lulled into a false sense of security in this well-lit space.

Having gorged, rather than go back out the way it came in, the insect might head straight for one of these false exits.  After all, the mouth is half hidden by its curling lip.

Disorientated and tired, like a fly that has been helplessly crashing into a glass window, the insect might try to settle on the slippery walls of the plant.  Unable to get a grip, it goes plunging down the spiralling tube straight into the pool at the bottom, which is kept filled with water pumped up from the ground.  The down-pointing hairs on the inner walls discourage any attempts of a soaked insect to climb back to freedom.  By the end of the summer, these carnivorous pitcher plants will be half-filled with insect remains, the sign of a successful season.

Cobra Lilies (Darlingtonia californica) are native to northern California and southern Oregon in the United States.

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