"Nyctinastic" plants explained

Pictured to the right is a three-leaf clover with holes generated by insects. Note the symmetry, which is explained at LiveScience: Each night at sunset, a handful of plants "fall asleep." Species as diverse as legumes and daisies curl up their leaves and petals for the evening and do not unfurl until morning.
Now, a new study suggests that plants may have been folding their leaves at night for more than 250 million years. By tracking the unique bite marks that insects inflict only upon folded leaves, the authors determined that one extinct group of plants were likely nyctinastic — the scientific term for plants curling up in response to darkness...
Charles Darwin described "sleep movements in plants" in 1880 in his book "The Power of Movement in Plants," but the phenomenon had already been documented as far back as 324 B.C. by Androsthenes of Thasos, an associate of Alexander the Great. It's hard to miss — stroll through any garden near dusk, and you'll likely notice a few flower species closing their petals...
But if plant sleeping behavior is a defense mechanism, it clearly does not work every time. In fact, one of the telltale signs of nyctinasty is that the plants' leaves are often pockmarked by perfectly symmetrical holes. Not unlike what happens when a child cuts shapes into folded paper to make a snowflake, any hole punched through a folded leaf by an insect will show up on both sides of that leaf when it opens.
Here is an image of a fossilized leaf depicting the same event:

More details and relevant links at LiveScience.