"Look at this!" said my dad, as he inserted the blunt end of his eyeglasses into my Venus fly trap.

The plant closed its fibrous mouth over the plastic ear pad, locking it in.

"Papa, you're killing it. It can only do that a few times before it dies, and you're not feeding it any food," I said, in my exhausted fourth-grade voice.

"BUT LOOK AT THIS!" said my dad. I walked to my room and shut the door. That plant was dead a couple of weeks later.

Although my $4 plant was ruined by this stunt, my dad was actually noting something fascinating about the Venus fly trap: it's remarkably quick response to an insect stepping into its mouth. The movement is so quick, one would be tempted to call it animal-like, instead of plant-like.

But what makes the famous carnivorous plant act so quickly? A new paper in the journal Current Biology spills the beans: Venus fly traps can count.

According to new research by a scientist who apparently spends a ton of his time around Venus fly traps, the plants depend on insects for food mostly when they live in soil devoid of nutrients (read: my parents' kitchen). When they go into carnivorous mode, they have to retain a lot of energy to perform the monumental task of closing their gargantuan mouths. So, when an insect steps his or her little foot onto the plant's surface, it has to be very careful to make sure that the insect is staying long enough for the plant to chow down. The magic number is two.

Once the insect has brushed up twice against the trigger hairs in the plant's mouth, it snaps shut in a fraction of a second. This is done via electrical impulses called "action potentials" or "APs." Two APs within about 20 seconds, and the plant identifies its prey as a moving insect, and locks it in for dinner. But the story doesn't end there.

A third AP triggers the plant's inner taxonomist, prompting it to figure out what kind of insect it has to work with. By the fifth AP, the plant begins to chemically salivate, picking up sodium from the insect and digesting needed nutrients.

Ironically, if the insect stopped moving after step #2, the plant's digestive process would theoretically stop, making it open its mouth again to seek more prey, and let its prisoner out. But like a human trapped in quicksand, the insect instinctively flails about, triggering the digestion process, and sealing its own fate.

In the experiment detailed in the new paper, the researchers fed crickets to the fly traps — one of the largest meals such a plant can expect. The average cricket stimulated one of the plant's hairs 63 times within the first hour of its digestion, suggesting a rather prolonged death. One would hope that some of these stimulations occur because the insect is rolling around in the trap, rather than struggling for survival. What we know for certain is that once the mouth opens up again, often 10 days later, nothing but a corpse remains.

The paper was published online today, in the journal Current Biology.

Photo: Hugo A. Quintero | Flickr

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